Showing papers by "European Southern Observatory published in 2012"
University of California, Berkeley1, Lawrence Berkeley National Laboratory2, Australian Astronomical Observatory3, Pontifical Catholic University of Chile4, Harvard University5, Hamilton College6, University of Utah7, University of Tokyo8, Michigan State University9, Space Telescope Science Institute10, California Institute of Technology11, University of Colorado Boulder12, University of California, Santa Cruz13, University of Waterloo14, University of Chicago15, University of Florida16, Stockholm University17, University of Minnesota18, National Institutes of Natural Sciences, Japan19, Leiden University20, Northwestern University21, University of Bonn22, University of California, Davis23, University of Washington24, Kyoto University25, Pennsylvania State University26, European Southern Observatory27, Lawrence Livermore National Laboratory28, University of Lisbon29, Texas A&M University30, University of Toronto31
TL;DR: In this article, Advanced Camera for Surveys, NICMOS and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey was presented.
Abstract: We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on board HST. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union.
1,784 citations
TL;DR: In this article, the star formation rate (SFR)-stellar mass (M{sub *}) relation in a self-consistent manner from 0 10 at 1 < z < 1.
Abstract: We study the star formation rate (SFR)-stellar mass (M{sub *}) relation in a self-consistent manner from 0 10 at 1 < z < 1.5), (2) red star-forming galaxies with low levels of dust obscuration and low-specific SFRs (11%), and (3) dusty, blue star-forming galaxies with high-specific SFRs (7%). The remaining 28% comprises quiescent galaxies. Galaxies on the 'normal' star formation sequence show strong trends of increasing dust attenuationmore » with stellar mass and a decreasing specific SFR, with an observed scatter of 0.25 dex. The dusty, blue galaxies reside in the upper envelope of the star formation sequence with remarkably similar spectral shapes at all masses, suggesting that the same physical process is dominating the stellar light. The red, low-dust star-forming galaxies may be in the process of shutting off and migrating to the quiescent population.« less
921 citations
Space Telescope Science Institute1, Spanish National Research Council2, University of the Basque Country3, Michigan State University4, Johns Hopkins University5, Tel Aviv University6, University of California, Berkeley7, California Institute of Technology8, European Southern Observatory9, Academia Sinica10, Leiden University11, University College London12, Pontifical Catholic University of Chile13, Rutgers University14, Carnegie Institution for Science15, Ohio State University16, INAF17, University of California, San Diego18, CERN19, Max Planck Society20
TL;DR: The Cluster Lensing And Supernova Survey with Hubble (CLASH) as mentioned in this paper is a 524-orbit Multi-Cycle Treasury Program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions.
Abstract: The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit Multi-Cycle Treasury Program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, 20 CLASH clusters are solely X-ray selected. The X-ray-selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (θ_Ein > 35" at z_s = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (σ_z ~ 0.02(1 + z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over eight epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6+2223 (z = 0.544).
910 citations
University of Bologna1, University of Barcelona2, INAF3, University of Edinburgh4, Centre national de la recherche scientifique5, University of Toulouse6, European Southern Observatory7, California Institute of Technology8, ETH Zurich9, Max Planck Society10, Paris Diderot University11, University of Vienna12, Spanish National Research Council13, University of Insubria14, Institute for the Physics and Mathematics of the Universe15, University of Nottingham16, National Taiwan Normal University17, Johns Hopkins University18, Space Telescope Science Institute19, Institut d'Astrophysique de Paris20, University of California, Santa Cruz21, University of California, Davis22, Lawrence Livermore National Laboratory23
TL;DR: In this paper, the authors presented new improved constraints on the Hubble parameter H(z) in the redshift range 0.15 -1.1, obtained from the differential spectroscopic evolution of early-type galaxies as a function of redshift.
Abstract: We present new improved constraints on the Hubble parameter H(z) in the redshift range 0.15 \textless z \textless 1.1, obtained from the differential spectroscopic evolution of early-type galaxies as a function of redshift. We extract a large sample of early-type galaxies ( 11000) from several spectroscopic surveys, spanning almost 8 billion years of cosmic lookback time (0.15 \textless z \textless 1.42). We select the most massive, red elliptical galaxies, passively evolving and without signature of ongoing star formation. Those galaxies can be used as standard cosmic chronometers, as firstly proposed by Jimenez & Loeb (2002), whose (life! Nit age evolution as a function of cosmic time directly probes H (z). We analyze the 4000 angstrom break (D4000) as a function of redshift, use stellar population synthesis models to theoretically calibrate the dependence of the differential age evolution on the differential D4000, and estimate the Hubble parameter taking into account both statistical and systematical errors. We provide 8 new measurements of H(z) (see table 4), and determine its change in H(z) to a precision of 5-12% mapping homogeneously the redshift range up to z 1.1; for the first time, we place a constraint on 11(z) at z not equal 0 with a precision comparable with the one achieved for the Hubble constant (about 5-6% at z similar to 0.2), and covered a redshift range (0.5 \textless z \textless 0.8) which is crucial to distinguish many different quintessence cosmologies. These measurements have been tested to best match a ACDM model, clearly providing a statistically robust indication that the Universe is undergoing an accelerated expansion. This method shows the potentiality to open a new avenue in constrain a variety of alternative cosmologies, especially when future surveys (e.g. Euclid) will open the possibility to extend it up to z similar to 2.
724 citations
European Southern Observatory1, Yale University2, Leiden University3, Max Planck Society4, Harvard University5, University of Wisconsin–Milwaukee6, University of Arizona7, University of California, Santa Cruz8, Tufts University9, Carnegie Learning10, California Institute of Technology11, University of Wisconsin-Madison12
TL;DR: 3D-HST as discussed by the authors is a near-infrared spectroscopic Treasury program with the Hubble Space Telescope for studying the physical processes that shape galaxies in the distant universe.
Abstract: We present 3D-HST, a near-infrared spectroscopic Treasury program with the Hubble Space Telescope for studying
the physical processes that shape galaxies in the distant universe. 3D-HST provides rest-frame optical spectra for
a sample of ∼7000 galaxies at 1 < z < 3.5, the epoch when ∼60% of all star formation took place, the number
density of quasars peaked, the first galaxies stopped forming stars, and the structural regularity that we see in
galaxies today must have emerged. 3D-HST will cover three quarters (625 arcmin^2) of the CANDELS Treasury
survey area with two orbits of primary WFC3/G141 grism coverage and two to four orbits with the ACS/G800L
grism in parallel. In the IR, these exposure times yield a continuum signal-to-noise ratio of ∼5 per resolution element
at H_140 ∼ 23.1 and a 5σ emission-line sensitivity of ∼5 × 10^(−17) erg s^−1 cm^(−2) for typical objects, improving by
a factor of ∼2 for compact sources in images with low sky background levels. The WFC3/G141 spectra provide
continuous wavelength coverage from 1.1 to 1.6μm at a spatial resolution of ∼0."13, which, combined with their
depth, makes them a unique resource for studying galaxy evolution. We present an overview of the preliminary
reduction and analysis of the grism observations, including emission-line and redshift measurements from combined
fits to the extracted grism spectra and photometry from ancillary multi-wavelength catalogs. The present analysis
yields redshift estimates with a precision of σ(z) = 0.0034(1 + z), or σ(v) ≈ 1000 km s^(−1). We illustrate how
the generalized nature of the survey yields near-infrared spectra of remarkable quality for many different types
of objects, including a quasar at z = 4.7, quiescent galaxies at z ∼ 2, and the most distant T-type brown dwarf
star known. The combination of the CANDELS and 3D-HST surveys will provide the definitive imaging and
spectroscopic data set for studies of the 1 < z < 3.5 universe until the launch of the James Webb Space Telescope.
723 citations
TL;DR: The first data release of the UltraVISTA near-infrared imaging survey of the COSMOS field is described in this paper, where stacked, sky-subtracted images in YJHK_s and narrow-band filters constructed from data collected during the first year of UltraVisTA observations are presented.
Abstract: In this paper we describe the first data release of the UltraVISTA near-infrared imaging survey of the COSMOS field. We summarise the key goals and design of the survey and provide a detailed description of our data reduction techniques. We provide stacked, sky-subtracted images in YJHK_s and narrow-band filters constructed from data collected during the first year of UltraVISTA observations. Our stacked images reach 5σAB depths in an aperture of 2″ diameter of ~25 in Y and ~24 in JHK_s bands and all have sub-arcsecond seeing. To this 5σ limit, our K_s catalogue contains 216 268 sources. We carry out a series of quality assessment tests on our images and catalogues, comparing our stacks with existing catalogues. The 1σ astrometric rms in both directions for stars selected with 17.0 < K_s(AB) < 19.5 is ~0.08″ in comparison to the publicly-available COSMOS ACS catalogues. Our images are resampled to the same pixel scale and tangent point as the publicly available COSMOS data and so may be easily used to generate multi-colour catalogues using this data. All images and catalogues presented in this paper are publicly available through ESO’s “phase 3” archiving and distribution system and from the UltraVISTA web site.
717 citations
University of Oxford1, University of California, Berkeley2, Centre national de la recherche scientifique3, Paris Diderot University4, University of Massachusetts Amherst5, European Southern Observatory6, Leiden University7, University of Lyon8, École Normale Supérieure9, Max Planck Society10, ASTRON11, Kapteyn Astronomical Institute12, University of Hertfordshire13, Swinburne University of Technology14, University of Toronto15
TL;DR: A study of the two-dimensional stellar kinematics for the large representative ATLAS3D sample of nearby early- type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models finds a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, implying that a galaxy’s IMF depends intimately on the galaxy's formation history.
Abstract: Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history
639 citations
Heidelberg University1, Institut d'Astrophysique de Paris2, European Southern Observatory3, University College London4, University of St Andrews5, University of Tasmania6, Niels Bohr Institute7, University of Warsaw8, University of Notre Dame9, University of Canterbury10, Space Telescope Science Institute11, Lawrence Livermore National Laboratory12, University of Rijeka13, University of Vienna14, University of Toulouse15, NASA Exoplanet Science Institute16, Osaka University17, University of Concepción18, University of Cambridge19
TL;DR: It is concluded that stars are orbited by planets as a rule, rather than the exception, and that of stars host Jupiter-mass planets 0.5–10 au (Sun–Earth distance) from their stars.
Abstract: Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17–30% of solar-like stars host a planet. Gravitational microlensing on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002–07) that reveals the fraction of bound planets 0.5–10 au (Sun–Earth distance) from their stars. We find that 17^(+16)_(-9)% of stars host Jupiter-mass planets (0.3–10 M_J, where M_J = 318 M_⊕ plus and M_⊕ plus is Earth’s mass). Cool Neptunes (10–30 M_⊕ plus) and super-Earths (5–10 M_⊕ plus) are even more common: their respective abundances per star are 52^(+22)_(-29)% and 62^(+35)_(-73)% . We conclude that stars are orbited by planets as a rule, rather than the exception.
623 citations
TL;DR: In this article, the star formation rate (SFR) - stellar mass (M*) relation in a self-consistent manner from 0 10 at 1 < z < 1.5 was studied.
Abstract: We study the star formation rate (SFR) - stellar mass (M*) relation in a self-consistent manner from 0 10 at 1 < z < 1.5), 2) red star-forming galaxies with low levels of dust obscuration and low specific SFRs (11%), and 3) dusty, blue star-forming galaxies with high specific SFRs (7%). The remaining 28% comprises quiescent galaxies. Galaxies on the "normal" star formation sequence show strong trends of increasing dust attenuation with stellar mass and a decreasing specific SFR, with an observed scatter of 0.25 dex (0.17 dex intrinsic scatter). The dusty, blue galaxies reside in the upper envelope of the star formation sequence with remarkably similar spectral shapes at all masses, suggesting that the same physical process is dominating the stellar light. The red, low-dust star-forming galaxies may be in the process of shutting off and migrating to the quiescent population.
505 citations
Liverpool John Moores University1, University of Western Australia2, University of St Andrews3, University of Sussex4, University of Sydney5, University of Melbourne6, European Southern Observatory7, Durham University8, Australian Astronomical Observatory9, University of Nottingham10, University of Edinburgh11, Monash University, Clayton campus12, University of Central Lancashire13, Australian National University14, Max Planck Society15
TL;DR: In this paper, the low-redshift field galaxy stellar mass function (GSMF) was determined from a sample of 5210 galaxies using a density-corrected maximum volume method.
Abstract: We determine the low-redshift field galaxy stellar mass function (GSMF) using an area of 143 deg 2 from the first three years of the Galaxy And Mass Assembly (GAMA) survey. The magnitude limits of this redshift survey are r < 19.4 mag over two-thirds and 19.8 mag over one-third of the area. The GSMF is determined from a sample of 5210 galaxies using a densitycorrected maximum volume method. This efficiently overcomes the issue of fluctuations in the number density versus redshift. With H0 = 70 km s −1 Mpc −1 , the GSMF is well described
485 citations
Herzberg Institute of Astrophysics1, Peking University2, Paris Diderot University3, Centre national de la recherche scientifique4, University of Paris5, University of Bonn6, Youngstown State University7, Case Western Reserve University8, Pontifical Catholic University of Chile9, University of Strasbourg10, University of Lyon11, European Southern Observatory12, University of Waterloo13, University of British Columbia14, Institut d'Astrophysique de Paris15, Queen's University16, University of Milan17, Keele University18, University of Toronto19, University of Cambridge20, Leiden University21, Carnegie Institution for Science22, Saint Mary's University23, University of Hawaii24, McMaster University25
TL;DR: The Next Generation Virgo Cluster Survey (NGVS) as discussed by the authors uses the 1 deg2 MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical imaging survey of the Virgo cluster, from its core to its virial radius.
Abstract: The Next Generation Virgo Cluster Survey (NGVS) is a program that uses the 1 deg2 MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical imaging survey of the Virgo cluster, from its core to its virial radius—covering a total area of 104 deg2—in the u*griz bandpasses. Thanks to a dedicated data acquisition strategy and processing pipeline, the NGVS reaches a point-source depth of g ≈ 25.9 mag (10σ) and a surface brightness limit of μ g ~ 29 mag arcsec–2 (2σ above the mean sky level), thus superseding all previous optical studies of this benchmark galaxy cluster. In this paper, we give an overview of the technical aspects of the survey, such as areal coverage, field placement, choice of filters, limiting magnitudes, observing strategies, data processing and calibration pipelines, survey timeline, and data products. We also describe the primary scientific topics of the NGVS, which include: the galaxy luminosity and mass functions; the color-magnitude relation; galaxy scaling relations; compact stellar systems; galactic nuclei; the extragalactic distance scale; the large-scale environment of the cluster and its relationship to the Local Supercluster; diffuse light and the intracluster medium; galaxy interactions and evolutionary processes; and extragalactic star clusters. In addition, we describe a number of ancillary programs dealing with "foreground" and "background" science topics, including the study of high-inclination trans-Neptunian objects; the structure of the Galactic halo in the direction of the Virgo Overdensity and Sagittarius Stream; the measurement of cosmic shear, galaxy-galaxy, and cluster lensing; and the identification of distant galaxy clusters, and strong-lensing events.
TL;DR: It is shown that adaptive optics has led to important advances in the authors' understanding of a multitude of astrophysical processes, and how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.
Abstract: Adaptive Optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach the diffraction limit and thus providing spatial resolution superior to that achievable from space with current or planned satellites. In this review we consider adaptive optics from the astrophysical perspective. We show that adaptive optics has led to important advances in our understanding of a multitude of astrophysical processes, and describe how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.
TL;DR: In this article, the authors use coagulation/fragmentation and disk-structure models to simulate the evolution of dust in a bumpy surface density profile, which they mimic with a sinusoidal disturbance.
Abstract: Aims. We attempt to explain grain growth to mm sized particles and their retention in the outer regions of protoplanetary disks, as observed at sub-mm and mm wavelengths, by investigating whether strong inhomogeneities in the gas density profiles can decelerate excessive radial drift and help the dust particles to grow.
Methods. We use coagulation/fragmentation and disk-structure models, to simulate the evolution of dust in a bumpy surface density profile, which we mimic with a sinusoidal disturbance. For different values of the amplitude and length scale of the bumps, we investigate the ability of this model to produce and retain large particles on million-year timescales. In addition, we compare the pressure inhomogeneities considered in this work with the pressure profiles that come from magnetorotational instability. Using the Common Astronomy Software Applications ALMA simulator, we study whether there are observational signatures of these pressure inhomogeneities that can be seen with ALMA.
Results. We present the conditions required to trap dust particles and the corresponding calculations predicting the spectral slope in the mm-wavelength range, to compare with current observations. Finally, we present simulated images using different antenna configurations of ALMA at different frequencies, to show that the ring structures will be detectable at the distances of either the Taurus Auriga or Ophiucus star-forming regions.
Pontifical Catholic University of Chile1, Princeton University2, University of Hertfordshire3, European Southern Observatory4, Atacama Large Millimeter Submillimeter Array5, University of Cambridge6, University of Edinburgh7, University of Manchester8, Queen Mary University of London9, University of La Serena10, University of Lisbon11, Instituto de Astronomía Teórica y Experimental12, INAF13, University of Warsaw14, University of Concepción15, Valparaiso University16, National University of Cordoba17, University of Florida18, National Scientific and Technical Research Council19, University of São Paulo20, National University of La Plata21, University of Padua22, University of Wisconsin–Whitewater23, Universidade Federal do Rio Grande do Sul24, University of Chile25, Peking University26, Kyung Hee University27, Max Planck Society28, University of Alicante29, University College London30, University of Cincinnati31, University of Leeds32, Ames Research Center33, UK Astronomy Technology Centre34, University of La Laguna35, Spanish National Research Council36, University of Southampton37, Saint Mary's University38, Australian Astronomical Observatory39, Macquarie University40, Andrés Bello National University41, Hartebeesthoek Radio Astronomy Observatory42, Aryabhatta Research Institute of Observational Sciences43, University of Kent44
TL;DR: The ESO VISTA public survey VISTA variables in the V�a L�ctea (VVV) started in 2010 and is expected to run for about five years.
Abstract: Context The ESO public survey VISTA variables in the V�a L�ctea (VVV) started in 2010 VVV targets 562 sq deg in the Galactic bulge and an adjacent plane region and is expected to run for about five years Aims: We describe the progress of the survey observations in the first observing season, the observing strategy, and quality of the data obtained Methods: The observations are carried out on the 4-m VISTA telescope in the ZYJHK s filters In addition to the multi-band imaging the variability monitoring campaign in the K s filter has started Data reduction is carried out using the pipeline at the Cambridge Astronomical Survey Unit The photometric and astrometric calibration is performed via the numerous 2MASS sources observed in each pointing Results: The first data release contains the aperture photometry and astrometric catalogues for 348 individual pointings in the ZYJHK s filters taken in the 2010 observing season The typical image quality is 09 arcsec {-10 arcsec} The stringent photometric and image quality requirements of the survey are satisfied in 100% of the JHK s images in the disk area and 90% of the JHK s images in the bulge area The completeness in the Z and Y images is 84% in the disk, and 40% in the bulge The first season catalogues contain 128 � 10 8 stellar sources in the bulge and 168 � 10 8 in the disk area detected in at least one of the photometric bands The combined, multi-band catalogues contain more than 163 � 10 8 stellar sources About 10% of these are double detections because of overlapping adjacent pointings These overlapping multiple detections are used to characterise the quality of the data The images in the JHK s bands extend typically 4 mag deeper than 2MASS The magnitude limit and photometric quality depend strongly on crowding in the inner Galactic regions The astrometry for K s = 15-18 mag has rms 35-175 mas Conclusions: The VVV Survey data products offer a unique dataset to map the stellar populations in the Galactic bulge and the adjacent plane and provide an exciting new tool for the study of the structure, content, and star-formation history of our Galaxy, as well as for investigations of the newly discovered star clusters, star-forming regions in the disk, high proper motion stars, asteroids, planetary nebulae, and other interesting objects Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179B-2002
ASTRON1, Kapteyn Astronomical Institute2, University of California, Berkeley3, European Southern Observatory4, École normale supérieure de Lyon5, Paris Diderot University6, University of Oxford7, University of Massachusetts Amherst8, Leiden University9, Max Planck Society10, University of Hertfordshire11, University of Toronto12, New Mexico Institute of Mining and Technology13
Abstract: We present the ATLAS3D H i survey of a volume-limited, complete sample of 166 nearby early-type galaxies (ETGs) brighter than MK=-21.5. The survey is mostly based on data taken with the Westerbork Synthesis Radio Telescope, which enables us to detect H i down to 5 x 1065 x 107 M? within the survey volume. We detect similar to 40 per cent of all ETGs outside the Virgo galaxy cluster and similar to 10 per cent of all ETGs inside it. This demonstrates that it is common for non-cluster ETGs to host H i. The morphology of the detected gas varies in a continuous way from regular, settled H i discs and rings to unsettled gas distributions (including tidal or accretion tails) and systems of clouds scattered around the galaxy. The majority of the detections consist of H i discs or rings (1/4 of all ETGs outside Virgo) so that if H i is detected in an ETG it is most likely distributed on a settled configuration. These systems come in two main types: small discs [ M?], which are confined within the stellar body and share the same kinematics of the stars; and large discs/rings [M(H i) up to 5 x 109 M?], which extend to tens of kpc from the host galaxy and are in half of the cases kinematically decoupled from the stars. Neutral hydrogen seems to provide material for star formation in ETGs. Galaxies containing H i within similar to 1Re exhibit signatures of on-going star formation in similar to 70 per cent of the cases, approximately five times more frequently than galaxies without central H i. The interstellar medium (ISM) in the centre of these galaxies is dominated by molecular gas, and in ETGs with a small gas disc the conversion of H i into H2 is as efficient as in spirals. The ETG H i mass function is characterized by M*similar to 2 x 109 M? and by a slope a similar to-0.7. Compared to spirals, ETGs host much less H i as a family. However, a significant fraction of all ETGs are as H i-rich as spiral galaxies. The main difference between ETGs and spirals is that the former lack the high-column-density H i typical of the bright stellar disc of the latter. The ETG H i properties vary with environment density in a more continuous way than suggested by the known Virgo versus non-Virgo dichotomy. We find an envelope of decreasing M(H i) and M(H i)/LK with increasing environment density. The gas-richest galaxies live in the poorest environments (as found also with CO observations), where the detection rate of star formation signatures is higher. Galaxies in the centre of Virgo have the lowest H i content, while galaxies at the outskirts of Virgo represent a transition region and can contain significant amounts of H i, indicating that at least a fraction of them has joined the cluster only recently after pre-processing in groups. Finally, we find an H i morphologydensity relation such that at low environment density (measured on a local scale) the detected H i is mostly distributed on large, regular discs and rings, while more disturbed H i morphologies dominate environment densities typical of rich groups. This confirms the importance of processes occurring on a galaxy-group scale for the evolution of ETGs.
TL;DR: In this paper, the authors investigated the spatial and density structure of the Rosette molecular cloud, irradiated by the NGC2244 cluster, and concluded that star-formation in Rosette is not globally triggered by the impact of UV-radiation.
Abstract: For many years feedback processes generated by OB-stars in molecular clouds, including expanding ionization fronts, stellar winds, or UV-radiation, have been proposed to trigger subsequent star formation. However, hydrodynamic models including radiation and gravity show that UV-illumination has little or no impact on the global dynamical evolution of the cloud. The Rosette molecular cloud, irradiated by the NGC2244 cluster, is a template region for triggered star-formation, and we investigated its spatial and density structure by applying a curvelet analysis, a filament-tracing algorithm (DisPerSE), and probability density functions (PDFs) on Herschel column density maps, obtained within the HOBYS key program. The analysis reveals not only the filamentary structure of the cloud but also that all known infrared clusters except one lie at junctions of filaments, as predicted by turbulence simulations. The PDFs of sub-regions in the cloud show systematic differences. The two UV-exposed regions have a double-peaked PDF we interprete as caused by shock compression. The deviations of the PDF from the log-normal shape typically associated with low- and high-mass star-forming regions at Av~3-4m and 8-10m, respectively, are found here within the very same cloud. This shows that there is no fundamental difference in the density structure of low- and high-mass star-forming regions. We conclude that star-formation in Rosette - and probably in high-mass star-forming clouds in general - is not globally triggered by the impact of UV-radiation. Moreover, star formation takes place in filaments that arose from the primordial turbulent structure built up during the formation of the cloud. Clusters form at filament mergers, but star formation can be locally induced in the direct interaction zone between an expanding HII--region and the molecular cloud.
Johns Hopkins University1, Space Telescope Science Institute2, Heidelberg University3, Siena College4, University of Science and Technology of China5, University College London6, Spanish National Research Council7, California Institute of Technology8, Pontifical Catholic University of Chile9, Leiden University10, University of the Basque Country11, Ikerbasque12, Michigan State University13, University of Copenhagen14, Rutgers University15, Carnegie Institution for Science16, Ohio State University17, European Southern Observatory18, Academia Sinica Institute of Astronomy and Astrophysics19, Max Planck Society20
TL;DR: In this paper, the authors report multiband observations of the cluster MACS J1149+2223 that have revealed (with high probability) a gravitationally magnified galaxy from the early Universe, at a redshift of z = 9.6 − 0.2 (that is, a cosmic age of 490 − 15 million years, or 3.6 per cent of the age of the Universe).
Abstract: Re-ionization of the intergalactic medium occurred in the early Universe at redshift z ≈ 6-11, following the formation of the first generation of stars. Those young galaxies (where the bulk of stars formed) at a cosmic age of less than about 500 million years (z ≲ 10) remain largely unexplored because they are at or beyond the sensitivity limits of existing large telescopes. Understanding the properties of these galaxies is critical to identifying the source of the radiation that re-ionized the intergalactic medium. Gravitational lensing by galaxy clusters allows the detection of high-redshift galaxies fainter than what otherwise could be found in the deepest images of the sky. Here we report multiband observations of the cluster MACS J1149+2223 that have revealed (with high probability) a gravitationally magnified galaxy from the early Universe, at a redshift of z = 9.6 ± 0.2 (that is, a cosmic age of 490 ± 15 million years, or 3.6 per cent of the age of the Universe). We estimate that it formed less than 200 million years after the Big Bang (at the 95 per cent confidence level), implying a formation redshift of ≲14. Given the small sky area that our observations cover, faint galaxies seem to be abundant at such a young cosmic age, suggesting that they may be the dominant source for the early re-ionization of the intergalactic medium.
TL;DR: In this article, the authors used the Vista Variables in the Via Lactea (VVV) ESO public survey data to measure extinction values in the complete area of the Galactic bulge covered by the survey at high resolution.
Abstract: Context. The Milky Way bulge is the nearest galactic bulge and the most readily accessible laboratory for studies of stellar populations in spheroids based on individual stellar abundances and kinematics. These studies are challenged by the strongly variable and often large extinction on a small spatial scale. Aims. We use the Vista Variables in the Via Lactea (VVV) ESO public survey data to measure extinction values in the complete area of the Galactic bulge covered by the survey at high resolution. Methods. We derive reddening values using the method described in Paper I. This is based on measuring the mean (J − Ks) color of red clump giants in small subfields of 2 � × 2 � to 6 � × 6 � in the following bulge area: −10.3 ◦ ≤ b ≤ +5.1 ◦ and −10.0 ◦ ≤ l ≤ +10.4 ◦ . To determine the reddening values E(J − Ks) for each region, we measure the RC color and compare it to the (J − Ks) color of RC stars measured in Baade’s Window, for which we adopt E(B − V) = 0.55. This allows us to construct a reddening map sensitive to small-scale variations minimizing the problems arising from differential extinction. Results. The significant reddening variations are clearly observed on spatial scales as small as 2 � . We find good agreement between our extinction measurements and Schlegel maps in the outer bulge, but, as already stated in the literature the Schlegel maps are unreliable for regions within |b| < 6 ◦ . In the inner regions, we compare our results with maps derived from DENIS and Spitzer surveys. While we find good agreement with other studies in the corresponding overlapping regions, our extinction map is of higher quality owing to both its higher resolution and a more complete spatial coverage of the bulge. We investigate the importance of differential reddening and demonstrate the need for high spatial resolution extinction maps for detailed studies of bulge stellar populations and structure. Conclusions. We present the first extinction map covering uniformly ∼315 sq. deg. of the Milky Way bulge at high spatial resolution. We consider a 30 arcmin window at a latitude of b = −4 ◦ , which corresponds to a frequently studied low extinction window, the so-called Baade’s Window, and find that its AKs values can vary by up to 0.1 mag. Larger extinction variations are observed at lower Galactic latitudes. The extinction variations on scales of up to 2 � −6 � must be taken into account when analyzing the stellar populations of the Galactic bulge.
Harvard University1, Max Planck Society2, California Institute of Technology3, University of Hawaii4, University of California, Riverside5, Space Telescope Science Institute6, University of Arizona7, European Southern Observatory8, National Autonomous University of Mexico9, ETH Zurich10, Carnegie Institution for Science11, Yale University12, Institute for the Physics and Mathematics of the Universe13, University of Bologna14
TL;DR: In this article, the authors used the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources in the Chandra COSMOS Survey.
Abstract: The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg^2 of the COSMOS field down to limiting depths of 1.9 × 10^(–16) erg cm^(–2) s^(–1) in the soft (0.5-2 keV) band, 7.3 × 10^(–16) erg cm^(–2) s^(–1) in the hard (2-10 keV) band, and 5.7 × 10^(–16) erg cm^(–2) s^(–1) in the full (0.5-10 keV) band. In this paper we report the i, K, and 3.6 μm identifications of the 1761 X-ray point sources. We use the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online. Making use of the large number of X-ray sources, we update the "classic locus" of active galactic nuclei (AGNs) defined 20 years ago in soft X-ray surveys and define a new locus containing 90% of the AGNs in the survey with full-band luminosity >10^(42) erg s^(–1). We present the linear fit between the total i-band magnitude and the X-ray flux in the soft and hard bands, drawn over two orders of magnitude in X-ray flux, obtained using the combined C-COSMOS and XMM-COSMOS samples. We focus on the X-ray to optical flux ratio (X/O) and we test its known correlation with redshift and luminosity, and a recently introduced anti-correlation with the concentration index (C). We find a strong anti-correlation (though the dispersion is of the order of 0.5 dex) between X/O computed in the hard band and C and that 90% of the obscured AGNs in the sample with morphological information live in galaxies with regular morphology (bulgy and disky/spiral), suggesting that secular processes govern a significant fraction of the black hole growth at X-ray luminosities of 10^(43)-10^(44.5) erg s^(–1). We also investigate the degree of obscuration of the sample using the hardness ratio, and we compare the X-ray color with the near-infrared to optical color.
TL;DR: In this paper, the authors proposed a scenario where blazars are classified as flat-spectrum radio quasars (FSRQs), BL Lacs, low synchrotron, or high synchoretron peaked objects according to a varying mix of the Doppler boosted radiation from the jet, the emission from the accretion disk, the broad line region, and the light from the host galaxy.
Abstract: We propose a scenario where blazars are classified as flat-spectrum radio quasars (FSRQs), BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying mix of the Doppler boosted radiation from the jet, the emission from the accretion disk, the broad line region, and the light from the host galaxy. In this framework the peak energy of the synchrotron power (ν S ) in blazars is independent of source type and of radio luminosity. We test this new approach, which builds upon unified schemes, using extensive Monte Carlo simulations and show that it can provide simple answers to a number of long-standing issues including, amongst others, the different cosmological evolution of BL Lacs selected in the radio and X-ray bands, the larger ν S peak values observed in BL Lacs, the fact that high synchrotron peaked blazars are always of the BL Lac type, and the existence of FSRQ/BL Lac transition objects. Objects so far classified as BL Lacs on the basis of their observed weak, or undetectable, emission lines are of two physically different classes: intrinsically weak lined objects, more common in X-ray selected samples, and heavily diluted broad lined sources, more frequent in radio selected samples, which explains some of the confusion in the literature. We also show that strong selection effects are the main cause of the diversity observed in radio and X-ray samples, and that the correlation between luminosity and ν S , that led to the proposal of the “blazar sequence”, is also a selection effect arising from the comparison of shallow radio and X-ray surveys, and to the fact that high ν S peak - high radio power objects have never been considered because their redshift is not measurable.
University of St Andrews1, University of Western Australia2, Liverpool John Moores University3, University of Nottingham4, University of Sydney5, Australian Astronomical Observatory6, Swinburne University of Technology7, European Southern Observatory8, University of Sussex9, Durham University10, University of Bristol11, University of Central Lancashire12, University of Melbourne13, Max Planck Society14
TL;DR: In this article, a single-Sersic two-dimensional (2D) model fits to 167 600 galaxies modelled independently in the ugrizYJHK bandpasses using reprocessed Sloan Digital Sky Survey Data Release Seven (SDSS DR7) and UKIRT Infrared Deep Sky Survey Large Area Survey imaging data available from the Galaxy And Mass Assembly (GAMA) data base is presented.
Abstract: We present single-Sersic two-dimensional (2D) model fits to 167 600 galaxies modelled independently in the ugrizYJHK bandpasses using reprocessed Sloan Digital Sky Survey Data Release Seven (SDSS DR7) and UKIRT Infrared Deep Sky Survey Large Area Survey imaging data available from the Galaxy And Mass Assembly (GAMA) data base. In order to facilitate this study we developed Structural Investigation of Galaxies via Model Analysis (sigma), an r wrapper around several contemporary astronomy software packages including source extractor, psf extractor and galfit 3. sigma produces realistic 2D model fits to galaxies, employing automatic adaptive background subtraction and empirical point spread function measurements on the fly for each galaxy in GAMA. Using these results, we define a common coverage area across the three GAMA regions containing 138 269 galaxies. We provide Sersic magnitudes truncated at 10re which show good agreement with SDSS Petrosian and GAMA photometry for low Sersic index systems (n 4), recovering as much as Δm= 0.5 mag in the r band. We employ a K-band Sersic index/u−r colour relation to delineate the massive (n > ∼2) early-type galaxies (ETGs) from the late-type galaxies (LTGs). The mean Sersic index of these ETGs shows a smooth variation with wavelength, increasing by 30 per cent from g through K. LTGs exhibit a more extreme change in Sersic index, increasing by 52 per cent across the same range. In addition, ETGs and LTGs exhibit a 38 and 25 per cent decrease, respectively, in half-light radius from g through K. These trends are shown to arise due to the effects of dust attenuation and stellar population/metallicity gradients within galaxy populations.
California Institute of Technology1, National Radio Astronomy Observatory2, Harvard University3, University of Michigan4, ASTRON5, Heidelberg University6, University of St Andrews7, Max Planck Society8, University of Illinois at Urbana–Champaign9, University of Maryland, College Park10, European Southern Observatory11, INAF12
TL;DR: In this article, the authors present dust continuum observations of the protoplanetary disk surrounding the pre-main-sequence star AS 209, spanning more than an order of magnitude in wavelength from 0.88 to 9.8mm.
Abstract: We present dust continuum observations of the protoplanetary disk surrounding the pre-main-sequence star AS 209, spanning more than an order of magnitude in wavelength from 0.88 to 9.8 mm. The disk was observed with subarcsecond angular resolution (02-05) to investigate radial variations in its dust properties. At longer wavelengths, the disk emission structure is notably more compact, providing model-independent evidence for changes in the grain properties across the disk. We find that physical models which reproduce the disk emission require a radial dependence of the dust opacity κν. Assuming that the observed wavelength-dependent structure can be attributed to radial variations in the dust opacity spectral index (β), we find that β(R) increases from β 1.5 for R 80 AU, inconsistent with a constant value of β across the disk (at the 10σ level). Furthermore, if radial variations of κν are caused by particle growth, we find that the maximum size of the particle-size distribution (a max) increases from submillimeter-sized grains in the outer disk (R 70 AU) to millimeter- and centimeter-sized grains in the inner disk regions (R 70 AU). We compare our observational constraint on a max(R) with predictions from physical models of dust evolution in protoplanetary disks. For the dust composition and particle-size distribution investigated here, our observational constraints on a max(R) are consistent with models where the maximum grain size is limited by radial drift.
TL;DR: The calibration of an astronomical spectrograph with a short-term Doppler shift repeatability of 2.5 cm s−1 is reported, which should make it possible to detect Earth-like planets in the habitable zone of star or even to measure the cosmic acceleration directly.
Abstract: The best spectrographs are limited in stability by their calibration light source. Laser frequency combs are the ideal calibrators for astronomical spectrographs. They emit a spectrum of lines that are equally spaced in frequency and that are as accurate and stable as the atomic clock relative to which the comb is stabilized. Absolute calibration provides the radial velocity of an astronomical object relative to the observer (on Earth). For the detection of Earth-mass exoplanets in Earth-like orbits around solar-type stars, or of cosmic acceleration, the observable is a tiny velocity change of less than 10 cm s(-1), where the repeatability of the calibration--the variation in stability across observations--is important. Hitherto, only laboratory systems or spectrograph calibrations of limited performance have been demonstrated. Here we report the calibration of an astronomical spectrograph with a short-term Doppler shift repeatability of 2.5 cm s(-1), and use it to monitor the star HD 75289 and recompute the orbit of its planet. This repeatability should make it possible to detect Earth-like planets in the habitable zone of star or even to measure the cosmic acceleration directly.
TL;DR: It is reported that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers, corresponding well to an effective ranking of the dynamical stage reached by stellar systems, thereby permitting a direct measure of the cluster dynamical age purely from observed properties.
Abstract: Globular clusters can be grouped into a few distinct families on the basis of the radial distribution of ‘blue stragglers’, stars with masses greater than those at the turn-off point on the main sequence; this grouping can yield a direct measure of the cluster’s dynamical age purely from observed properties. Star clusters formed at the same cosmic time may differ in the way they evolve dynamically, and a reliable method for determining cluster dynamical age would be a valuable tool for future studies. This study of a class of stars known as blue stragglers—among the most massive and luminous objects in old clusters—demonstrates that globular clusters can be grouped into a few distinct families based on the radial distribution of blue stragglers. Such a grouping allows a direct measure of the cluster dynamical age from purely observed properties. Globular star clusters that formed at the same cosmic time may have evolved rather differently from the dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre1. Therefore clusters with the same chronological age may have reached quite different stages of their dynamical history (that is, they may have different ‘dynamical ages’). Blue straggler stars have masses greater2 than those at the turn-off point on the main sequence and therefore must be the result of either a collision3,4 or a mass-transfer event5,6,7. Because they are among the most massive and luminous objects in old clusters, they can be used as test particles with which to probe dynamical evolution. Here we report that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers. This grouping corresponds well to an effective ranking of the dynamical stage reached by stellar systems, thereby permitting a direct measure of the cluster dynamical age purely from observed properties.
TL;DR: In this article, the growth of the red sequence through the number density and structural evolution of a sample of young and old quiescent galaxies at 0 1 that are almost non-existent at z 1 were studied.
Abstract: We study the growth of the red sequence through the number density and structural evolution of a sample of young and old quiescent galaxies at 0 1 that are almost non-existent at z 1 are consistent with a simple model in which all old quiescent galaxies were once identified as post-starburst galaxies. We find that the overall population of quiescent galaxies have smaller sizes and slightly more elongated shapes at higher redshift, in agreement with other recent studies. Interestingly, the most recently quenched galaxies at 1 < z < 2 are not larger, and possibly even smaller, than older galaxies at those redshifts. This result is inconsistent with the idea that the evolution of the average size of quiescent galaxies is largely driven by continuous transformations of larger, star-forming galaxies: in that case, the youngest quiescent galaxies would also be the largest. Instead, mergers or other mechanisms appear to be required to explain the size growth of quiescent galaxies from z = 2 to the present.
TL;DR: In this article, the authors presented twenty-three transit light curves and seven occultation light curves for the ultra short period planet WASP -43 b, in addition to eight new measurements of the radial velocity of the star.
Abstract: We present twenty-three transit light curves and seven occultation light curves for the ultra-short period planet WASP -43 b, in addition to eight new measurements of the radial velocity of the star. Thanks to this extensive data set, we improve significantly t he parameters of the system. Notably, the largely improved precision on the stellar density (2.41± 0.08ρ⊙) combined with constraining the age to be younger than a Hubble time allows us to break the degeneracy of the stellar solution mentioned in the discovery paper. The resulting stellar mass and size are 0.717± 0.025 M⊙ and 0.667± 0.011 R⊙. Our deduced physical parameters for the planet are 2.034± 0.052 MJup and 1.036± 0.019 RJup. Taking into account its level of irradiation, the high dens ity of the planet favors an old age and a massive core. Our deduced orbital eccentricity, 0.0035 +0.0060 −0.0025 , is consistent with a fully circularized orbit. We detect th e emission of the planet at 2.09µm at better than 11-σ, the deduced occultation depth being 1560± 140 ppm. Our detection of the occultation at 1.19µm is marginal (790± 320 ppm) and more observations are needed to confirm it. We pla ce a 3-σ upper limit of 850 ppm on the depth of the occultation at∼0.9µm. Together, these results strongly favor a poor redistribu tion of the heat to the night-side of the planet, and marginally favor a model with no day-side temperature inversion.
TL;DR: In this article, the authors presented a homogeneous subsample of 69 Swift GRB-selected galaxies spanning a very wide redshift range and made the sample optically unbiased through simple and well-defined selection criteria based on the high-energy properties of the bursts and their positions on the sky.
Abstract: Long-duration gamma-ray bursts (GRBs) are powerful tracers of star-forming galaxies. We have defined a homogeneous subsample of 69 Swift GRB-selected galaxies spanning a very wide redshift range. Special attention has been devoted to making the sample optically unbiased through simple and well-defined selection criteria based on the high-energy properties of the bursts and their positions on the sky. Thanks to our extensive follow-up observations, this sample has now achieved a comparatively high degree of redshift completeness, and thus provides a legacy sample, useful for statistical studies of GRBs and their host galaxies. In this paper, we present the survey design and summarize the results of our observing program conducted at the ESO Very Large Telescope (VLT) aimed at obtaining the most basic properties of galaxies in this sample, including a catalog of R and Ks magnitudes and redshifts. We detect the host galaxies for 80% of the GRBs in the sample, although only 42% have Ks-band detections, which confirms that GRB-selected host galaxies are generally blue. The sample is not uniformly blue, however, with two extremely red objects detected. Moreover, galaxies hosting GRBs with no optical/NIR afterglows, whose identification therefore relies on X-ray localizations, are significantly brighter and redder than those with an optical/NIR afterglow. This supports a scenario where GRBs occurring in more massive and dusty galaxies frequently suffer high optical obscuration. Our spectroscopic campaign has resulted in 77% now having redshift measurements, with a median redshift of 2.14 ± 0.18. TOUGH alone includes 17 detected z> 2 Swift GRB host galaxies suitable for individual and statistical studies—a substantial increase over previous samples. Seven hosts have detections of the Lyα emission line and we can exclude an early indication that Lyα emission is ubiquitous among GRB hosts, but confirm that Lyα is stronger in GRB-selected galaxies than in flux-limited samples of Lyman break galaxies.
TL;DR: In this article, the IRAM Plateau de Bure Interferometer was used to detect the 158 µm [C II] emission line and underlying dust continuum in the host galaxy of the quasar ULAS J112001.3 (hereafter J1120+0641) at z 7.48+064124.
Abstract: Using the IRAM Plateau de Bure Interferometer, we report the detection of the 158 {mu}m [C II] emission line and underlying dust continuum in the host galaxy of the quasar ULAS J112001.48+064124.3 (hereafter J1120+0641) at z 7.0842 {+-} 0.0004. This is the highest redshift detection of the [C II] line to date, and allows us to put the first constraints on the physical properties of the host galaxy of J1120+0641. The [C II] line luminosity is 1.2 {+-} 0.2 Multiplication-Sign 10{sup 9} L{sub Sun }, which is a factor {approx}4 lower than observed in a luminous quasar at z = 6.42 (SDSS J1148+5251). The underlying far-infrared (FIR) continuum has a flux density of 0.61 {+-} 0.16 mJy, similar to the average flux density of z {approx} 6 quasars that were not individually detected in the rest-frame FIR. Assuming that the FIR luminosity of L{sub FIR} = 5.8 Multiplication-Sign 10{sup 11}-1.8 Multiplication-Sign 10{sup 12} L{sub Sun} is mainly powered by star formation, we derive a star formation rate in the range 160-440 M{sub Sun} yr{sup -1} and a total dust mass in the host galaxy of 6.7 Multiplication-Sign 10{sup 7}-5.7 Multiplication-Sign 10{sup 8} M{sub Sun} (both numbers have significant uncertainties givenmore » the unknown nature of dust at these redshifts). The [C II] line width of {sigma}{sub V} = 100 {+-} 15 km s{sup -1} is among the smallest observed when compared to the molecular line widths detected in z {approx} 6 quasars. Both the [C II] and dust continuum emission are spatially unresolved at the current angular resolution of 2.0 Multiplication-Sign 1.7 arcsec{sup 2} (corresponding to 10 Multiplication-Sign 9 kpc{sup 2} at the redshift of J1120+0641).« less
TL;DR: In this article, the authors investigated the reliability of the many accretion tracers currently used to measure the mass accretion rate in low-mass, young stars and the accuracy of the correlations between these secondary tracers (mainly accretion line luminosities) found in the literature.
Abstract: We present high-quality, medium resolution X-shooter/VLT spectra in the range 300-2500 nm for a sample of 12 very low-mass stars in the Orionis cluster. The sample includes eight stars with evidence of disks from Spitzer and four without, with masses ranging from 0.08 to 0.3 M . The aim of this first paper is to investigate the reliability of the many accretion tracers currently used to measure the mass accretion rate in low-mass, young stars and the accuracy of the correlations between these secondary tracers (mainly accretion line luminosities) found in the literature. We use our spectra to measure the accretion luminosity from the continuum excess emission in the UV and visual; the derived mass accretion rates range from 10 9 M yr 1 down to 5 10 11 M yr 1 , allowing us to investigate the behavior of the accretion-driven emission lines in very-low mass accretion rate regimes. We compute the luminosity of ten accretion-driven emission lines, from the UV to the near-IR, all obtained simultaneously. In general, most of the secondary tracers correlate well with the accretion luminosity derived from the continuum excess emission. We recompute the relationships between the accretion luminosities and the line luminosities, we confirm the validity of the correlations given in the literature, with the possible exception of H . Metallic lines, such as the CaII IR triplet or the Na I line at 589.3 nm, show a larger dispersion. When looking at individual objects, we find that the Hydrogen recombination lines, from the UV to the near-IR, give good and consistent measurements of Lacc often in better agreement than the uncertainties introduced by the adopted correlations. The average Lacc derived from several Hydrogen lines, measured simultaneously, have a much reduced error. This suggests that some of the spread in the literature correlations may be due to the use of non-simultaneous observations of lines and continuum. Three stars in our sample deviate from this behavior, and we discuss them individually.
European Southern Observatory1, Centre national de la recherche scientifique2, INAF3, Cardiff University4, University of Manchester5, Ghent University6, Peking University7, University of Paris-Sud8, Max Planck Society9, University of Copenhagen10, Imperial College London11, University of California, Irvine12, University of Cambridge13, University of Chile14
TL;DR: In this article, the authors combine new Herschel/SPIRE sub-millimeter observations with existing multiwavelength data to investigate the dust scaling relations of the Herschel Reference Survey, a magnitude-, volume-limited sample of similar to 300 nearby galaxies in different environments.
Abstract: We combine new Herschel/SPIRE sub-millimeter observations with existing multiwavelength data to investigate the dust scaling relations of the Herschel Reference Survey, a magnitude-, volume-limited sample of similar to 300 nearby galaxies in different environments. We show that the dust-to-stellar mass ratio anti-correlates with stellar mass, stellar mass surface density and NUV - r colour across the whole range of parameters covered by our sample. Moreover, the dust-to-stellar mass ratio decreases significantly when moving from late-to early-type galaxies. These scaling relations are similar to those observed for the Hi gas-fraction, supporting the idea that the cold dust is tightly coupled to the cold atomic gas component in the interstellar medium. We also find a weak increase of the dust-to-Hi mass ratio with stellar mass and colour but no trend is seen with stellar mass surface density. By comparing galaxies in different environments we show that, although these scaling relations are followed by both cluster and field galaxies, Hi-deficient systems have, at fixed stellar mass, stellar mass surface density and morphological type systematically lower dust-to-stellar mass and higher dust-to-Hi mass ratios than Hi-normal/field galaxies. This provides clear evidence that dust is removed from the star-forming disk of cluster galaxies but the effect of the environment is less strong than what is observed in the case of the Hi disk. Such effects naturally arise if the dust disk is less extended than the Hi and follows more closely the distribution of the molecular gas phase, i.e., if the dust-to-atomic gas ratio monotonically decreases with distance from the galactic center.