Showing papers by "Lise Christensen published in 2011"
TL;DR: X-shooter as mentioned in this paper is the first 2nd generation instrument of the ESO Very Large Telescope (VLT), which was installed at the Cassegrain focus of UT2 in 2009.
Abstract: X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope(VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R~4,000 - 17,000, depending on wavelength and slit width) with fixed echelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8"x4" Integral Field Unit as an alternative to the 11" long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.
1,031 citations
TL;DR: In this paper, the second part of a series reporting on the results from a survey conducted with the ESO VLT/X-shooter spectrograph was presented, where high-metallicity damped Lyman alpha absorbers (DLAs) with th
Abstract: This is the second paper of a series reporting on the results from a survey conducted with the ESO VLT/X-shooter spectrograph. We target high-metallicity damped Lyman alpha absorbers (DLAs) with th ...
123 citations
TL;DR: X-shooter as discussed by the authors is the first 2nd generation instrument of the ESO Very Large Telescope (VLT), which was installed at the Cassegrain focus of UT2 in 2009.
Abstract: X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope(VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R~4,000 - 17,000, depending on wavelength and slit width) with fixed echelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8"x4" Integral Field Unit as an alternative to the 11" long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.
97 citations
University College London1, King's College London2, University of Cambridge3, University of Copenhagen4, Aarhus University5, Stanford University6, University of Southern California7, Duke University8, Pomeranian Medical University9, University of Texas Health Science Center at Houston10, Roswell Park Cancer Institute11, University of Hawaii at Manoa12, University of Ulm13, Fred Hutchinson Cancer Research Center14, University of Erlangen-Nuremberg15, Royal Brisbane and Women's Hospital16, University of California, Los Angeles17, German Cancer Research Center18
TL;DR: Evidence is shown for the involvement of a common allele of STAG3 in the development of epithelial ovarian cancer and the potential role of tSNPs in these nine genes in ovarian cancer development is evaluated.
Abstract: Common germline genetic variation in the population is associated with susceptibility to epithelial ovarian cancer. Microcell-mediated chromosome transfer and expression microarray analysis identified nine genes associated with functional suppression of tumorogenicity in ovarian cancer cell lines; AIFM2, AKTIP, AXIN2, CASP5, FILIP1L, RBBP8, RGC32, RUVBL1 and STAG3. Sixty-three tagging single nucleotide polymorphisms (tSNPs) in these genes were genotyped in 1,799 invasive ovarian cancer cases and 3,045 controls to look for associations with disease risk. Two SNPs in RUVBL1, rs13063604 and rs7650365, were associated with increased risk of serous ovarian cancer [HetOR = 1.42 (1.15-1.74) and the HomOR = 1.63 (1.10-1.42), p-trend = 0.0002] and [HetOR = 0.97 (0.80-1.17), HomOR = 0.74 (0.58-0.93), p-trend = 0.009], respectively. We genotyped rs13063604 and rs7650365 in an additional 4,590 cases and 6,031 controls from ten sites from the United States, Europe and Australia; however, neither SNP was significant in Stage 2. We also evaluated the potential role of tSNPs in these nine genes in ovarian cancer development by testing for allele-specific loss of heterozygosity (LOH) in 286 primary ovarian tumours. We found frequent LOH for tSNPs in AXIN2, AKTIP and RGC32 (64, 46 and 34%, respectively) and one SNP, rs1637001, in STAG3 showed significant allele-specific LOH with loss of the common allele in 94% of informative tumours (p = 0.015). Array comparative genomic hybridisation indicated that this nonrandom allelic imbalance was due to amplification of the rare allele. In conclusion, we show evidence for the involvement of a common allele of STAG3 in the development of epithelial ovarian cancer.
63 citations
INAF1, Spanish National Research Council2, North Carolina State University3, University of Copenhagen4, Technische Universität München5, University of Warwick6, University of Valencia7, University of Iceland8, University of Colorado Boulder9, University of Hawaii10, Southwest Research Institute11, University of Leicester12, University of Chicago13, University of Oslo14
TL;DR: The case of GRB 090426 at z = 2.609, whose optical spectrum indicates an almost fully ionized medium together with a low column density of neutral hydrogen was studied in this article.
Abstract: Long duration gamma-ray bursts are commonly associated with the deaths of massive stars. Spectroscopic studies using the afterglow as a light source provide a unique opportunity to unveil the medium surrounding it, probing the densest region of their galaxies. This material is usually in a low ionization state and at large distances from the burst site, hence representing the normal interstellar medium in the galaxy. Here we present the case of GRB 090426 at z= 2.609, whose optical spectrum indicates an almost fully ionized medium together with a low column density of neutral hydrogen. For the first time, we also observe variations in the Lyα absorption line. Photoionization modelling shows that we are probing material from the vicinity of the burst (∼80 pc). The host galaxy is a complex of two luminous interacting galaxies, which might suggest that this burst could have occurred in an isolated star-forming region outside its host galaxy created in the interaction of the two galaxies.
63 citations
TL;DR: The case of GRB 090426 is presented, whose optical spectrum indicates an almost fully ionized medium together with a low column density of neutral hydrogen, and for the first time, variations in the Lyα absorption line are observed.
Abstract: Long duration gamma-ray bursts are commonly associated with the deaths of massive stars. Spectroscopic studies using the afterglow as a light source provide a unique opportunity to unveil the medium surrounding it, probing the densest region of their galaxies. This material is usually in a low ionisation state and at large distances from the burst site, hence representing the normal interstellar medium in the galaxy. Here we present the case of GRB 090426 at z=2.609, whose optical spectrum indicates an almost fully ionised medium together with a low column density of neutral hydrogen. For the first time, we also observe variations in the Ly alpha absorption line. Photoionisation modeling shows that we are probing material from the vicinity of the burst (~80 pc). The host galaxy is a complex of two luminous interacting galaxies, which might suggest that this burst could have occurred in an isolated star-forming region outside its host galaxy created in the interaction of the two galaxies.
62 citations
TL;DR: In this article, a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35 < z < 6.7 observed with low-resolution optical spectra.
Abstract: We present a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35 < z < 6.7 observed with low-resolution optical spectra. The composite spectrum covers the wavelength range 700-6600 A in the rest frame and has a mean signal-to-noise ratio of 150 per 1 A pixel and reaches a maximum of ~300 in the range 2500-3500 A. Equivalent widths are measured from metal absorption lines from the Lyα line to ~5200 A, and associated metal and hydrogen lines are identified between the Lyman break and Lyα line. The average transmission within the Lyman forest is consistent with that found along quasar lines of sight. We find a temporal variation in fine-structure lines when dividing the sample into bursts observed within 2 hr from their trigger and those observed later. Other lines in the predominantly neutral gas show variations too, but this is most likely a random effect caused by weighting of individual strong absorption lines and which mimics a temporal variation. Bursts characterized with high- or low-prompt GRB energy release produce afterglows with similar absorption line strengths, and likewise for bursts with bright or faint optical afterglows. Bursts defined as dark from their optical to X-ray spectral index have stronger absorption lines relative to the optically bright bursts. The composite spectrum has strong Ca II and Mg II absorption lines as commonly found in dusty galaxies, however, we find no evidence for dust or a significant molecular content based on the non-detection of diffuse interstellar bands. Compared to starburst galaxy spectra, the GRB composite has much stronger fine-structure lines, while metal absorption lines are weaker.
54 citations
TL;DR: In this paper, a damped Lyα absorber (DLA) is observed at a higher redshift in the spectrum of the brighter member of a quasar pair at z ∼ 1.929 with a separation of 3.3 arcsec on the sky.
Abstract: Context. Q 0151+048 is a physical quasar (QSO) pair at z ∼ 1.929 with a separation of 3.3 arcsec on the sky. In the spectrum of the brighter member of this pair, Q 0151+048A, a damped Lyα absorber (DLA) is observed at a higher redshift. We have previously detected the host galaxies of both QSOs, as well as a Lyα blob whose emission surrounding Q 0151+048A extends over 5×3.3 arcsec. Aims. We seek to constrain the geometry of the system and understand the possible relations between the DLA, the Lyα blob, and the two QSOs. We also aim at characterizing the former two objects in more detail. Methods. To study the nature of the Lyα blob, we performed low-resolution, long-slit spectroscopy with the slit aligned with the extended emission. We also observed the whole system using the medium-resolution VLT/X-shooter spectrograph and the slit aligned with the two QSOs. The systemic redshift of both QSOs was determined from rest-frame optical emission lines redshifted into the NIR. We employed line-profile fitting technique, to measure metallicities and the velocity width of low-ionization metal absorption lines associated to the DLA and photo-ionization modeling to characterize the DLA further. Results. We measure systemic redshifts of zem(A) = 1.92924± 0.00036 and zem(B) = 1.92863± 0.00042 from the H β and Hα emission lines, respectively. In other words, the two QSOs have identical redshifts within 2σ. From the width of Balmer emission lines and the strength of the rest-frame optical continuum, we estimate the masses of the black holes of the two QSOs to be 109.33 M and 108.38 M for Q 0151+048A and Q 0151+048B, respectively. We then use the correlation between black hole mass and dark matter halo mass to infer the mass of the dark matter halos hosting the two QSOs: 1013.74 M and 1013.13 M for Q 0151+048A and Q 0151+048B, respectively. We observe a velocity gradient along the major axis of the Lyα blob consistent with the rotation curve of a large disk galaxy, but it may also be caused by gas inflow or outflow. We detect residual continuum in the DLA trough, which we interpret as emission from the host galaxy of Q 0151+048A. The derived H0 column density of the DLA is log NH0 = 20.34 ± 0.02 cm−2. Metal column densities are also determined for a number of low-ionization species resulting in an overall metallicity of 0.01 Z . We detect C ii∗, which allows us to make a physical model of the DLA cloud. Conclusions. From the systemic redshifts of the QSOs, we conclude that the Lyα blob is associated with Q 0151+048A rather than with the DLA. The DLA must be located in front of both the Lyα blob and Q 0151+048A at a distance greater than 30 kpc and has a velocity relative to the blob of 640 ± 70 km s−1. The two quasars accrete at normal Eddington ratios. The DM halo of this double quasar will grow to the mass of our local supercluster at z = 0. We point out that those objects therefore form an ideal laboratory to study the physical interactions in a z = 2 precursor of our local supercluster.
34 citations
TL;DR: In this article, the authors performed low-resolution spectroscopy with the slit aligned with the extended emission of Q0151+048A (qA) and QB (qB) to estimate the masses of the black holes of the two QSOs.
Abstract: Q0151+048 is a physical QSO pair at z ~ 1.929 with a separation of 3.3 arcsec on the sky. In the spectrum of Q0151+048A (qA), a DLA is observed at a higher redshift. We have previously detected the host galaxies of both QSOs, as well as a Lya blob. We performed low-resolution spectroscopy with the slit aligned with the extended emission. We also observed the system using the medium-resolution VLT/X-shooter spectrograph and the slit aligned with the two QSOs. We measure systemic redshifts of zem(A)=1.92924{\pm}0.00036 and zem(B)=1.92863{\pm}0.00042 from the H{\beta} and H{\alpha} emission lines, respectively. We estimate the masses of the black holes of the two QSOs to be 10^9.33 M{\odot} and 10^8.38 M{\odot} for qA and qB, respectively. From this we infered the mass of the dark matter halos hosting the two QSOs: 10^13.74 M{\odot} and 10^13.13 M{\odot} for qA and qB, respectively. We observe a velocity gradient along the major axis of the Lya blob consistent with the rotation curve of a large disk galaxy, but it may also be caused by gas inflow or outflow. We detect residual continuum in the DLA trough which we interpret as emission from the host galaxy of qA. The derived H0 column density of the DLA is log NH0 = 20.34 {\pm} 0.02. Metal column densities results in an overall metallicity of 0.01 Z{\odot}. We detect CII* which allows us to make a physical model of the DLA cloud. From the systemic redshifts of the QSOs, we conclude that the Lya blob is associated with qA rather than with the DLA. The DLA must be located in front of both the Lya blob and qA at a distance larger than 30 kpc. The two QSOs accrete at normal eddington ratios. The DM halo of this double quasar will grow to the mass of our local super-cluster at z=0. We point out that those objects therefore form an ideal laboratory to study the physical interactions in a z=2 pre-cursor of our local super-cluster.
33 citations
TL;DR: In this article, the authors present the first mid-infrared spectrum of a GRB host, HG 031203, allowing both low and high-resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS).
Abstract: Gamma-ray burst (GRB) host galaxies have been studied extensively in optical photometry and spectroscopy. Here we present the first mid-infrared spectrum of a GRB host, HG 031203. It is one of the nearest GRB hosts at z = 0.1055, allowing both low- and high-resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS). Medium-resolution UV to K-band spectroscopy with the X-shooter spectrograph on the Very Large Telescope is also presented, along with Spitzer IRAC and MIPS photometry, as well as radio and submillimeter observations. These data allow us to construct a UV to radio spectral energy distribution with almost complete spectroscopic coverage from 0.3 to 35 {mu}m of a GRB host galaxy for the first time, potentially valuable as a template for future model comparisons. The IRS spectra show strong, high-ionization fine structure line emission indicative of a hard radiation field in the galaxy-in particular the [S IV]/[S III] and [Ne III]/[Ne II] ratios-suggestive of strong ongoing star formation and a very young stellar population. The absence of any polycyclic aromatic hydrocarbon emission supports these conclusions, as does the probable hot peak dust temperature, making HG 031203 similar to the prototypical blue compact dwarf galaxy (BCD), II Zw 40. The selection ofmore » HG 031203 via the presence of a GRB suggests that it might be a useful analog of very young star-forming galaxies in the early universe, and hints that local BCDs may be used as more reliable analogs of star formation in the early universe than typical local starbursts. We look at the current debate on the ages of the dominant stellar populations in z {approx} 7 and z {approx} 8 galaxies in this context. The nebular line emission is so strong in HG 031203 that at z {approx} 7, it can reproduce the spectral energy distributions of z-band dropout galaxies with elevated IRAC 3.6 and 4.5 {mu}m fluxes without the need to invoke a 4000 A break. Indeed, photometry of HG 031203 shows elevation of the broadband V-magnitude at a level similar to the IRAC elevation in stacked z-band dropouts, solely due to its strong [O III] line emission.« less
33 citations
TL;DR: In this article, the 8 o'clock arc of a gravitationally lensed galaxy was analyzed using the X-shooter spectrograph on the Very Large Telescope (HST).
Abstract: We present the analysis of new near-infrared, intermediate-resolution spectra of the gravitationally lensed galaxy "the 8 o'clock arc" at zsys = 2.7350 obtained with the X-shooter spectrograph on the Very Large Telescope. These rest-frame optical data, combined with Hubble and Spitzer Space Telescopes images, provide very valuable information, which nicely complement our previous detailed rest-frame UV spectral analysis, and make the 8 o'clock arc one of the better understood "normal" star-forming galaxies at this early epoch of the history of the Universe. From high-resolution HST images, we reconstruct the morphology of the arc in the source plane, and identify that the source is formed of two majors parts, the main galaxy component and a smaller blob separated by 1.2 kpc in projected distance. The blob, with a twice larger magnification factor, is resolved in the X-shooter spectra. The multi-Gaussian fitting of detected nebular emission lines and the spectral energy distribution modeling of the available multi-wavelength photometry provide the census of gaseous and stellar dust extinctions, gas-phase metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical masses for both the main galaxy and the blob. As a result, the 8 o'clock arc shows a marginal trend for a more attenuated ionized gas than stars, and supports a dependence of the dust properties on the SFR. With a high specific star-formation rate, SSFR = 33 ± 19 Gyr-1, this lensed Lyman-break galaxy deviates from the mass-SFR relation, and is characterized by a young age of 40+25-20 Myr and a high gas fraction of about 72%. The 8 o'clock arc satisfies the fundamental mass, SFR, and metallicity relation, and favors that it holds up beyond z ≃ 2.5. We believe that the blob, with a gas mass Mgas = (2.2 ± 0.9) × 109 Ms (one order of magnitude lower than the mass of the galaxy), a half-light radius r1/2 = 0.53 ± 0.05 kpc, a star-formation rate SFRHα = 33 ± 19 Ms yr-1, and in rotation around the main core of the galaxy, is one of these star-forming clumps commonly observed in z > 1 star-forming galaxies, because it is characterized by very similar physical properties. The knowledge of detailed physical properties of these clumps is a very useful input to models that aim to predict the formation and evolution of these clumps within high-redshift objects. Based on X-shooter observations made with the European Southern Observatory VLT/Kueyen telescope, Paranal, Chile, collected under the programme ID No. 284.A-5006(A).Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute.
TL;DR: The results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue as part of a very long baseline interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south, were presented in this paper.
Abstract: We present the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue as part of a very long baseline interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south. We made the observations with the 3.58 m European Southern Observatory New Technology Telescope. We obtained redshifts for 30 quasars and one radio galaxy, with a further seven objects being probable BL Lac objects with featureless spectra. Of the remainder, four were clear misidentifications with Galactic stars and five had low signal-to-noise spectra and could not be classified. These results, in combination with new VLBI data of the radio sources with redshifts more than 2, add significantly to the existing data needed to refine the distribution of source proper motions over the celestial sphere.
TL;DR: In this article, the results of a deep (J ∼ 21 at 5σ) infrared photometric survey of a 0.95-deg2 area in the central region of the Upper Sco association were presented.
Abstract: We present the results of a deep ( J ∼ 21 at 5σ) infrared photometric survey of a 0.95-deg2 area in the central region of the Upper Sco association. The photometric observations consist of a deep Y + J -band image obtained with the Wide Field Camera on the United Kingdom Infra-Red Telescope (UKIRT) with part coverage in Z complemented by the methane ON and OFF imaging survey conducted with the Wide-field InfraRed Camera on the Canada–France–Hawaii Telescope. We have selected five potential T-type objects belonging to the Upper Sco association on the basis of their blue methane colours and their J − CH 4off colours. We have also identified a sample of seven to eight Upper Sco member candidates bridging the gap between known cluster M types and our new T-type candidates. These candidates were selected based on their positions in various colour–magnitude diagrams, and they follow the sequence of known Upper Sco members identified in the UKIRT Infrared Deep Sky Survey Galactic Clusters Survey. We present additional membership constraints using proper motion estimates from the multiple epochs available with us. We also present optical and near-infrared spectra obtained with the X-Shooter spectrograph on the Very Large Telescope for five L-type candidates covering the 0.6–2.5 μm wavelength range, none of which is confirmed as a young brown dwarf. We discuss the lack of detection of new candidate members as well as the possible turn-down in the Upper Sco mass function as we are approaching the fragmentation limit.
TL;DR: In this paper, the authors used the VIMOS integral field spectrograph to map the emission line properties in a sample of 24 star forming galaxies selected from the SDSS database.
Abstract: We have used the VIMOS integral field spectrograph to map the emission line properties in a sample of 24 star forming galaxies selected from the SDSS database. In this data paper we present and describe the sample, and explore some basic properties of SDSS galaxies with resolved emission line fields. We fit the Halpha+[NII] emission lines in each spectrum to derive maps of continuum, Halpha flux, velocity and velocity dispersion. The Halpha, Hbeta, [NII] and [OIII] emission lines are also fit in summed spectra for circular annuli of increasing radius. A simple mass model is used to estimate dynamical mass within 10 kpc, which compared to estimates of stellar mass shows that between 10 and 100% of total mass is in stars. We present plots showing the radial behaviour of EW[Halpha], u-i colour and emission line ratios. Although EW[Halpha] and u-i colour trace current or recent star formation, the radial profiles are often quite different. Whilst line ratios do vary with annular radius, radial gradients in galaxies with central line ratios typical of AGN or LINERS are mild, with a hard component of ionization required out to large radii. We use our VIMOS maps to quantify the fraction of Halpha emission contained within the SDSS fibre, taking the ratio of total Halpha flux to that of a simulated SDSS fibre. A comparison of the flux ratios to colour-based SDSS extrapolations shows a 175% dispersion in the ratio of estimated to actual corrections in normal star forming galaxies, with larger errors in galaxies containing AGN. We find a strong correlation between indicators of nuclear activity: galaxies with AGN-like line ratios and/or radio emission frequently show enhanced dispersion peaks in their cores, requiring non-thermal sources of heating. Altogether, about half of the galaxies in our sample show no evidence for nuclear activity or non-thermal heating.
TL;DR: In this article, the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the ICRC, as part of a very long baseline interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south.
Abstract: We present the results of spectroscopic observations of the optical counterparts of 47 southern radio sources from the candidate International Celestial Reference Catalogue (ICRC), as part of a Very Long Baseline Interferometry (VLBI) program to strengthen the celestial reference frame, especially in the south. The observations were made with the 3.58-meter European Southern Observatory New Technology Telescope (NTT). We obtained redshifts for 30 quasars and one radio galaxy, with a further 7 objects being probable BL Lac objects with featureless spectra. Of the remainder, four were clear misidentifications with Galactic stars and five had low signal-to-noise spectra and could not be classified. These results, in combination with new VLBI data of the radio sources with redshifts more than 2, add significantly to the existing data needed to refine the distribution of source proper motions over the celestial sphere.
TL;DR: In this article, the authors studied the strong gravitational lensing system number 5 identified by the CAmbridge Sloan Survey Of Wide ARcs in the skY (CASSOWARY).
Abstract: We study the strong gravitational lensing system number 5 identified by the CAmbridge Sloan Survey Of Wide ARcs in the skY (CASSOWARY). In this system, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at redshift 0.388. The average projected angular distance of the multiple images from the primary lens is 12.6 kpc, corresponding to approximately 1.3 times the value of the galaxy effective radius. The observed positions of the multiple images are well reproduced by a model in which the total mass distribution of the deflector is described in terms of two singular isothermal sphere profiles and a small external shear component. The values of the effective velocity dispersions of the two lens galaxies are 328+7− 8 and 350+17− 18 km s−1. The best-fitting lensing model predicts magnification values larger than 2 for each multiple image and a total magnification factor of 17. By modelling the lens galaxy spectral energy distributions, we measure lens luminous masses of (3.09 ± 0.30) × 1011 and (5.87 ± 0.58) × 1011 M⊙ and stellar mass-to-light ratios of 2.5 ± 0.3 and 2.8 ± 0.3 M⊙ L−1⊙, i (in the observed i band). These values are used to disentangle the luminous and dark matter components in the vicinity of the multiple images. We estimate that the dark over total mass ratio projected within a cylinder centred on the primary lens and with a radius of 12.6 kpc is 0.8 ± 0.1. Inside the effective radii of the two galaxies, we measure projected total mass-to-light ratios of 12.6 ± 1.4 and 13.1 ± 1.7 M⊙ L−1⊙, i. We contrast these measurements with the typical values found at similar distances (in units of the effective radius) in isolated lens galaxies and show that the amount of dark matter present in these lens galaxies is almost a factor 4 larger than in field lens galaxies with comparable luminous masses. Data and models are therefore consistent with interpreting the lens of this system as a galaxy group. We infer that the overdense environment and dark matter concentration in these galaxies must have affected the assembly of the lens luminous mass components, resulting in the large values of the galaxy effective radii. We conclude that further multidiagnostics analyses on the internal properties of galaxy groups have the potential of providing us a unique insight into the complex baryonic and dark matter physics interplay that rules the formation of cosmological structures.
TL;DR: In this paper, the rest-frame UV to optical spectrum of the gravitationally lensed galaxy, the 8 o'clock arc at z = 2.735, was obtained with the X-shooter spectrograph.
Abstract: We present the rest-frame UV to optical spectrum of the gravitationally lensed galaxy, the “8 o'clock arc” at z = 2.735, obtained with the X-shooter spectrograph. This is one of the rare comprehensive study of a high-redshift star-forming galaxy, usually not feasible due to the faintness of these objects. The spectrum of the 8 o'clock arc is rich in stellar and interstellar absorption features and in nebular emission features. Their analysis allowed us to derive most of the physical properties characterizing the galaxy. From HST images, we reconstruct the morphology of the arc in the source plane and confirm that we resolve a clump in rotation around the main core of galaxy in our X-shooter spectrum (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this article, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at Redshift 0.388 and 0.8 +/- 0.1.
Abstract: We study the strong gravitational lensing system number 5 identified by the CASSOWARY survey. In this system, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at redshift 0.388. The observed positions of the multiple images are well reproduced by a model in which the total mass distribution of the deflector is described in terms of two singular isothermal sphere profiles. By modelling the lens galaxy spectral energy distributions, we measure the lens luminous masses and stellar mass-to-light ratios. These values are used to disentangle the luminous and dark matter components in the vicinity of the multiple images. We estimate that the dark over total mass ratio projected within a cylinder centred on the primary lens and with a radius of 12.6 kpc is 0.8 +/- 0.1. We contrast these measurements with the typical values found at similar distances (in units of the effective radius) in isolated lens galaxies and show that the amount of dark matter present in these lens galaxies is almost a factor four larger than in field lens galaxies with comparable luminous masses. Data and models are therefore consistent with interpreting the lens of this system as a galaxy group. We infer that the overdense environment and dark matter concentration in these galaxies must have affected the assembly of the lens luminous mass components. We conclude that further multi-diagnostics analyses on the internal properties of galaxy groups have the potential of providing us a unique insight into the complex baryonic and dark-matter physics interplay that rules the formation of cosmological structures.
TL;DR: In this paper, the results of a deep (J ~ 21 mag at 5 sigma) infrared photometric survey of a 0.95 square degree area in the central region of the Upper Sco association were presented.
Abstract: We present the results of a deep (J ~ 21 mag at 5 sigma) infrared photometric survey of a 0.95 square degree area in the central region of the Upper Sco association. The photometric observations consist of a deep (Y+J)-band images obtained with the WFCAM camera on the UKIRT InfraRed Telescope (UKIRT) with partly coverage in Z complemented by methane ON and OFF conducted with WIRCam on the Canada France Hawaii Telescope. We have selected five potential T-type objects belonging to the Upper Sco association on the basis of their blue methane colours and their J-CH4off colours. We have also identified a sample of 7-8 Upper Sco member candidates bridging the gap between known cluster M-types and our new T-type candidates. These candidates were selected based on their positions in various colour-magnitude diagrams and they follow the sequence of known Upper Sco members identified in the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS). We present additional membership constraints using proper motion estimates from the multiple epochs available to us. We also present optical and near-infrared spectra obtained with the X--Shooter spectrograph on the Very Large Telescope for five L-type candidates covering the 0.6 to 2.5 micron wavelength range, none of them being confirmed as a young brown dwarf. We discuss the lack of detection of new candidate members as well as the possible turn down in the USco mass function as we are approaching the fragmentation limit.
TL;DR: In this paper, X-shooter observations of star-burst galaxies at 0 < z < 6 from commissioning runs, science verification, and regular observations, and demonstrates the capability of the new instrument in this competitive field.
Abstract: In the last couple of decades hundreds of studies have explored the nature of star-forming galaxies at different redshifts. This contribution focuses on X-shooter observations of star-burst galaxies at 0 < z < 6 from commissioning runs, science verification, and regular observations, and demonstrates the capability of the new instrument in this competitive field. Observations of gravitationally lensed galaxies show that X-shooter has no limitation in the redshift desert (1.4 < z < 2) where the strong optical emission lines are shifted to the near-IR region. Physical properties of galaxies, such as masses, metallicities, abundance ratios, and star formation rates can be derived from observations with relatively short integration times for faint galaxies. The simultaneous UV to near-IR spectral coverage makes derivation of physical quantities more reliable because there are no differential slit losses as may occur when observations from different optical and near-IR instruments are used. Over the entire redshift range, spectra of faint galaxies will allow us to better measure stellar ages and dominating ionisation sources compared to broad band spectral energy distribution measurements (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)