Showing papers in "The Astrophysical Journal in 2005"
TL;DR: This paper considers the requirements and implementation constraints on a framework that simultaneously enables an efficient discretization with associated hierarchical indexation and fast analysis/synthesis of functions defined on the sphere and demonstrates how these are explicitly satisfied by HEALPix.
Abstract: HEALPix the Hierarchical Equal Area isoLatitude Pixelization is a versatile structure for the pixelization of data on the sphere. An associated library of computational algorithms and visualization software supports fast scientific applications executable directly on discretized spherical maps generated from very large volumes of astronomical data. Originally developed to address the data processing and analysis needs of the present generation of cosmic microwave background experiments (e.g., BOOMERANG, WMAP), HEALPix can be expanded to meet many of the profound challenges that will arise in confrontation with the observational output of future missions and experiments, including, e.g., Planck, Herschel, SAFIR, and the Beyond Einstein inflation probe. In this paper we consider the requirements and implementation constraints on a framework that simultaneously enables an efficient discretization with associated hierarchical indexation and fast analysis/synthesis of functions defined on the sphere. We demonstrate how these are explicitly satisfied by HEALPix.
5,518 citations
Sloan Fellows1, University of Arizona2, New York University3, University of Pittsburgh4, University of Pennsylvania5, Massachusetts Institute of Technology6, Institute for Advanced Study7, University of Washington8, Fermilab9, Princeton University10, Apache Corporation11, Spanish National Research Council12, Eötvös Loránd University13, University of Tokyo14, University of Chicago15, Johns Hopkins University16, University of Colorado Boulder17, Space Telescope Science Institute18, University of Michigan19, University of Edinburgh20, Rochester Institute of Technology21, Lawrence Berkeley National Laboratory22, Pennsylvania State University23, Adler Planetarium24, University of Hawaii25
TL;DR: In this paper, a large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey is presented, which demonstrates the linear growth of structure by gravitational instability between z ≈ 1000 and the present and confirms a firm prediction of the standard cosmological theory.
Abstract: We present the large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey. The survey region covers 0.72h −3 Gpc 3 over 3816 square degrees and 0.16 < z < 0.47, making it the best sample yet for the study of large-scale structure. We find a well-detected peak in the correlation function at 100h −1 Mpc separation that is an excellent match to the predicted shape and location of the imprint of the recombination-epoch acoustic oscillations on the low-redshift clustering of matter. This detection demonstrates the linear growth of structure by gravitational instability between z ≈ 1000 and the present and confirms a firm prediction of the standard cosmological theory. The acoustic peak provides a standard ruler by which we can measure the ratio of the distances to z = 0.35 and z = 1089 to 4% fractional accuracy and the absolute distance to z = 0.35 to 5% accuracy. From the overall shape of the correlation function, we measure the matter density mh 2 to 8% and find agreement with the value from cosmic microwave background (CMB) anisotropies. Independent of the constraints provided by the CMB acoustic scale, we find m = 0.273 ±0.025+0.123(1+ w0)+0.137K. Including the CMB acoustic scale, we find that the spatial curvature is K = −0.010 ± 0.009 if the dark energy is a cosmological constant. More generally, our results provide a measurement of cosmological distance, and hence an argument for dark energy, based on a geometric method with the same simple physics as the microwave background anisotropies. The standard cosmological model convincingly passes these new and robust tests of its fundamental properties. Subject headings: cosmology: observations — large-scale structure of the universe — distance scale — cosmological parameters — cosmic microwave background — galaxies: elliptical and lenticular, cD
4,428 citations
TL;DR: Galaxy Evolution Explorer (GALEX) as mentioned in this paper performed the first space UV sky survey, including imaging and grism surveys in two bands (1350-1750 and 1750-2750?).
Abstract: We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on 2003 April 28. GALEX is performing the first space UV sky survey, including imaging and grism surveys in two bands (1350-1750 and 1750-2750 ?). The surveys include an all-sky imaging survey (mAB 20.5), a medium imaging survey of 1000 deg2 (mAB 23), a deep imaging survey of 100 deg2 (mAB 25), and a nearby galaxy survey. Spectroscopic (slitless) grism surveys (R = 100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys in other bands. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the relationship of the UV and global star formation rate in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 2 and probe the physical drivers of star formation in galaxies. The GALEX mission includes a guest investigator program, supporting the wide variety of programs made possible by the first UV sky survey.
2,410 citations
TL;DR: In this article, the authors derived ages, total metallicities, and element ratios of 124 early-type galaxies in high and low-density environments, and analyzed the data by comparison with mock galaxy samples created through Monte Carlo simulations taking the typical average observational errors into account.
Abstract: The aim of this paper is to set constraints on the epochs of early-type galaxy formation through the archaeology of the stellar populations in local galaxies. Using our models of absorption-line indices that account for variable abundance ratios, we derive ages, total metallicities, and element ratios of 124 early-type galaxies in high- and low-density environments. The data are analyzed by comparison with mock galaxy samples created through Monte Carlo simulations taking the typical average observational errors into account, in order to eliminate artifacts caused by correlated errors. We find that all three parameters, age, metallicity, and ?/Fe ratio, are correlated with velocity dispersion. We show that these results are robust against recent revisions of the local abundance pattern at high metallicities. To recover the observed scatter we need to assume an intrinsic scatter of about 20% in age, 0.08?dex in [Z/H], and 0.05?dex in [?/Fe]. All low-mass objects with M* 1010 M? (? 130 km s-1) show evidence for the presence of intermediate-age stellar populations with low ?/Fe ratios. About 20% of the intermediate-mass objects with 1010 M*/M? 1011 [110 ?/(km s-1) 230; both elliptical and lenticular galaxies] must have either a young subpopulation or a blue horizontal branch. On the basis of the above relationships, valid for the bulk of the sample, we show that the Mg-? relation is mainly driven by metallicity, with similar contributions from the ?/Fe ratio (23%) and age (17%). We further find evidence for an influence of the environment on the stellar population properties. Massive early-type galaxies in low-density environments seem on average ~2?Gyr younger and slightly (~0.05-0.1?dex) more metal-rich than their counterparts in high-density environments. No offsets in the ?/Fe ratios are instead detected. With the aid of a simple chemical evolution model, we translate the derived ages and ?/Fe ratios into star formation histories. We show that most star formation activity in early-type galaxies is expected to have happened between redshifts ~3 and 5 in high-density environments and between redshifts 1 and 2 in low-density environments. We conclude that at least 50% of the total stellar mass density must have already formed at z ~ 1, in good agreement with observational estimates of the total stellar mass density as a function of redshift. Our results suggest that significant mass growth in the early-type galaxy population below z ~ 1 must be restricted to less massive objects, and a significant increase of the stellar mass density between redshifts 1 and 2 should be present, caused mainly by the field galaxy population. The results of this paper further imply the presence of vigorous star formation episodes in massive objects at z ~ 2-5 and evolved elliptical galaxies around z ~ 1, both observationally identified as SCUBA galaxies and extremely red objects, respectively.
1,668 citations
TL;DR: In this paper, the authors identify a subset of 850 stars that have Doppler observations sufficient to detect uniformly all planets with radial velocity semiamplitudes K > 30 m s-1 and orbital periods shorter than 4 yr, and determine that fewer than 3% of stars with -0.5 + 0.3 dex, 25% of observed stars have detected gas giant planets.
Abstract: We have recently carried out spectral synthesis modeling to determine Teff, log g, v sin i, and [Fe/H] for 1040 FGK-type stars on the Keck, Lick, and Anglo-Australian Telescope planet search programs. This is the first time that a single, uniform spectroscopic analysis has been made for every star on a large Doppler planet search survey. We identify a subset of 850 stars that have Doppler observations sufficient to detect uniformly all planets with radial velocity semiamplitudes K > 30 m s-1 and orbital periods shorter than 4 yr. From this subset of stars, we determine that fewer than 3% of stars with -0.5 +0.3 dex, 25% of observed stars have detected gas giant planets. A power-law fit to these data relates the formation probability for gas giant planets to the square of the number of metal atoms. High stellar metallicity also appears to be correlated with the presence of multiple-planet systems and with the total detected planet mass. This data set was examined to better understand the origin of high metallicity in stars with planets. None of the expected fossil signatures of accretion are observed in stars with planets relative to the general sample: (1) metallicity does not appear to increase as the mass of the convective envelopes decreases, (2) subgiants with planets do not show dilution of metallicity, (3) no abundance variations for Na, Si, Ti, or Ni are found as a function of condensation temperature, and (4) no correlations between metallicity and orbital period or eccentricity could be identified. We conclude that stars with extrasolar planets do not have an accretion signature that distinguishes them from other stars; more likely, they are simply born in higher metallicity molecular clouds.
1,624 citations
Abstract: We have obtained spectroscopic redshifts using the Keck I telescope for a sample of 73 submillimeter galaxies (SMGs), with a median 850 μm flux density of 5.7 mJy, for which precise positions are available through their faint radio emission. The galaxies lie at redshifts out to z = 3.6, with a median redshift of 2.2 and an interquartile range z = 1.7-2.8. Modeling a purely submillimeter flux-limited sample, based on the expected selection function for our radio-identified sample, suggests a median redshift of 2.3, with a redshift distribution remarkably similar to the optically and radio-selected quasars. The observed redshift distributions are similar for the active galactic nucleus (AGN) and starburst subsamples. The median RAB is 24.6 for the sample. However, the dust-corrected ultraviolet (UV) luminosities of the galaxies rarely hint at the huge bolometric luminosities indicated by their radio/submillimeter emission, with the effect that the true luminosity can be underestimated by a median factor of ~120 for SMGs with pure starburst spectra. Radio and submillimeter observations are thus essential to select the most luminous high-redshift galaxies. The 850 μm, radio, and redshift data are used to estimate the dust temperatures and characterize photometric redshifts. Using 450 μm measurements for a subset of our sample, we confirm that a median dust temperature of Td = 36 ± 7 K, derived on the assumption that the local far-infrared (FIR)-radio correlation applies at high redshift, is reasonable. Individual 450 μm detections are consistent with the local radio-FIR relation holding at z ~ 2. This median Td is lower than that estimated for similarly luminous IRAS 60 μm galaxies locally. We demonstrate that dust temperature variations make it impossible to estimate redshifts for individual SGMs to better than Δz 1 using simple long-wavelength photometric methods. We calculate total infrared and bolometric luminosities (the median infrared luminosity estimated from the radio is 8.5 × 1012 L☉), construct a luminosity function, and quantify the strong evolution of the submillimeter population across z = 0.5-3.5 relative to local IRAS galaxies. We use the bolometric luminosities and UV-spectral classifications to determine a lower limit to the AGN content of the population and measure directly the varying the contribution of highly obscured, luminous galaxies to the luminosity density history of the universe for the first time. We conclude that bright submillimeter galaxies contribute a comparable star formation density to Lyman break galaxies at z = 2-3, and including galaxies below our submillimeter flux limit, this population may be the dominant site of massive star formation at this epoch. The rapid evolution of SMGs and QSO populations contrasts with that seen in bolometrically lower luminosity galaxy samples selected in the rest-frame UV and suggests a close link between SMGs and the formation and evolution of the galactic halos that host QSOs.
1,335 citations
TL;DR: In this paper, the authors presented a new table for low-temperature Rosseland and Planck mean opacities from Alexander & Ferguson, which includes more grain species and updated optical constants.
Abstract: Previous computations of low-temperature Rosseland and Planck mean opacities from Alexander & Ferguson areupdatedandexpanded.Thenewcomputationsincludeamorecompleteequationofstate(EOS)withmoregrain species and updated optical constants. Grains are now explicitly included in thermal equilibrium in the EOS calculation, which allows for a much wider range of grain compositions to be accurately included than was previously the case. The inclusion of high-temperature condensates such as Al2O3 and CaTiO3 significantly affects the total opacityoveranarrowrangeoftemperaturesbeforetheappearanceofthefirstsilicategrains.Thenewopacitytables are tabulated for temperatures ranging from 30,000 to 500 K with gas densities from 10 � 4 to 10 � 19 gc m � 3 .C omparisons with previous Rosseland mean opacity calculations are discussed. At high temperatures, the agreement with OPAL and Opacity Project is quite good. Comparisons at lower temperatures are more divergent as a result of differences in molecular and grain physics included in different calculations. The computation of Planck mean opacities performed with the opacity sampling method is shown to require a very large number of opacity sampling wavelength points; previously published results obtained with fewer wavelength points are shown to be significantly in error. Methods for requesting or obtaining the new tables are provided. Subject heading gs: atomic data — equation of state — methods: numerical — molecular data
1,273 citations
TL;DR: In this paper, it was shown that large-scale galactic winds driven by momentum deposition are an efficient mechanism for feedback during the formation of galaxies and that these winds can expel a significant fraction of the gas in a galaxy.
Abstract: We investigate large-scale galactic winds driven by momentum deposition. Momentum injection is provided by (1) radiation pressure produced by the continuum absorption and scattering of photons on dust grains and (2) supernovae (momentum injection by supernovae is important even if the supernova energy is radiated away). Radiation can be produced by a starburst or active galactic nucleus (AGN) activity. We argue that momentum- driven winds are an efficient mechanism for feedback during the formation of galaxies. We show that above a limiting luminosity, momentum deposition from star formation can expel a significant fraction of the gas in a galaxy. The limiting, Eddington-like luminosity is LM ' (4fgc=G)� 4 ,w hereis the galaxy velocity dispersion and fg is the gas fraction; the subscript M refers to momentum driving. A starburst that attains LM moderates its star formation rate and its luminosity does not increase significantly further. We argue that elliptical galaxies attain this limitduring theirgrowthatz k1andthatthisisthe originofthe Faber-Jackson relation.We showthatLymanbreak galaxies and ultraluminous infrared galaxies have luminosities near LM. Since these starbursting galaxies account for a significant fraction of the star formation atz k1, this supports our hypothesis that much of the observed stellar mass in early-type galaxies was formed during Eddington-limited star formation. Star formation is unlikely to efficiently remove gas from very small scales in galactic nuclei, i.e., scales much smaller than that of a nuclear starburst. This gas is available to fuel a central black hole (BH). We argue that a BH clears gas out of its galactic nucleus when the luminosity of the BH itself reachesLM. This shuts off the fuel supply to the BH and may also terminate star formation in the surrounding galaxy. As a result, the BH mass is fixed to be MBH '( fges=� G 2 )� 4 , wherees is the electron scattering opacity. This limit is in accord with the observed MBH-� relation. Subject headingg galaxies: formation — galaxies: fundamental parameters — galaxies: general — galaxies: starburst — intergalactic medium
1,093 citations
TL;DR: In this article, the authors describe a local, linear instability in a Keplerian disk of solids and gas in which the two components mutually interact via aerodynamic drag, which generates radial drift and triggers unstable modes.
Abstract: Interpenetrating streams of solids and gas in a Keplerian disk produce a local, linear instability. The two components mutually interact via aerodynamic drag, which generates radial drift and triggers unstable modes. The secular instability does not require self-gravity, yet it generates growing particle-density perturbations that could seed planetesimal formation. Growth rates are slower than dynamical but faster than radial drift timescales. Growth rates, like streaming velocities, are maximized for marginal coupling (stopping times comparable to dynamical times). Fastest growth occurs when the solid-to-gas density ratio is order unity and feedback is strongest. Curiously, growth is strongly suppressed when the densities are too nearly equal. The relation between background drift and wave properties is explained by analogy with Howard's semicircle theorem. The three-dimensional, two-fluid equations describe a sixth-order (in the complex frequency) dispersion relation. A terminal velocity approximation allows simplification to an approximate cubic dispersion relation. To describe the simplest manifestation of this instability, we ignore complicating (but possibly relevant) factors such as vertical stratification, dispersion of particle sizes, turbulence, and self-gravity. We consider applications to planetesimal formation and compare our work to other studies of particle-gas dynamics.
1,075 citations
TL;DR: In this paper, the authors derived an analytic prediction for the star formation rate in environments ranging from normal galactic disks to starbursts and ULIRGs in terms of the observables of those systems.
Abstract: We derive an analytic prediction for the star formation rate in environments ranging from normal galactic disks to starbursts and ULIRGs in terms of the observables of those systems. Our calculation is based on three premises: (1) star formation occurs in virialized molecular clouds that are supersonically turbulent; (2) the density distribution within these clouds is lognormal, as expected for supersonic isothermal turbulence; and (3) stars form in any subregion of a cloud that is so overdense that its gravitational potential energy exceeds the energy in turbulent motions. We show that a theory based on this model is consistent with simulations and with the observed star formation rate in the Milky Way. We use our theory to derive the Kennicutt-Schmidt law from first principles and make other predictions that can be tested by future observations. We also provide an algorithm for estimating the star formation rate that is suitable for inclusion in numerical simulations.
1,043 citations
TL;DR: In this paper, the authors used a hybrid semianalytic plus N-body approach to distinguish between the evolution of light and dark matter in accreted satellites, which is essential to produce a realistic stellar halo, with mass and density profile much like that of our own Galaxy, and a surviving satellite population that matches the observed number counts and structural parameter distributions of the satellite galaxies of the Milky Way.
Abstract: If the favored hierarchical cosmological model is correct, then the Milky Way system should have accreted � 100– 200 luminous satellite galaxies in the past � 12 Gyr. We model this process using a hybrid semianalytic plus N-body approach that distinguishes explicitly between the evolution of light and dark matter in accreted satellites. This distinction is essential to our ability to produce a realistic stellar halo, with mass and density profile much like that of our own Galaxy, and a surviving satellite population that matches the observed number counts and structural parameter distributions of the satellite galaxies of the Milky Way. Our accreted stellar halos have density profiles that typically drop off with radius faster than the dark matter and follow power laws at rk30 kpc with � / r � � , � ’ 3 4. They are well fit by Hernquist profiles over the full radial range. We find that stellar halos are assembled from the inside out, with the majority of mass (� 80%) coming from the � 15 most massive accretion events. The satellites that contributetothestellarhalohavemedianaccretiontimes of � 9Gyrinthepast,whilesurvivingsatellitesystems have median accretion times of � 5 Gyr in the past. This implies that stars associated with the inner halo should be quite differentchemicallyfromstarsinsurvivingsatellitesandalsofromstarsintheouterhaloorthoseliberatedinrecent disruptionevents.Webrieflydiscusstheexpectedspatialstructureandphase-spacestructureforhalosformedinthismanner. Searches for this type of structure offer a direct test of whether cosmology is indeed hierarchical on small scales. Subject headingg dark matter — galaxies: dwarf — galaxies: evolution — galaxies: formation — galaxies: halos — galaxies: kinematics and dynamics — Galaxy: evolution — Galaxy: formation — Galaxy: halo — Galaxy: kinematics and dynamics — Local Group
TL;DR: In this article, the Spitzer Space Telescope mid-infrared colors, derived from the IRAC Shallow Survey, of nearly 10,000 spectroscopically identified sources from the AGN and Galaxy Evolution Survey, were used to identify active galaxies.
Abstract: Mid-infrared photometry provides a robust technique for identifying active galaxies. While the ultraviolet to mid-infrared (λ 5 μm) continuum of stellar populations is dominated by the composite blackbody curve and peaks at approximately 1.6 μm, the ultraviolet to mid-infrared continuum of active galactic nuclei (AGNs) is dominated by a power law. Consequently, with a sufficient wavelength baseline, one can easily distinguish AGNs from stellar populations. Mirroring the tendency of AGNs to be bluer than galaxies in the ultraviolet, where galaxies (and stars) sample the blue, rising portion of stellar spectra, AGNs tend to be redder than galaxies in the mid-infrared, where galaxies sample the red, falling portion of the stellar spectra. We report on Spitzer Space Telescope mid-infrared colors, derived from the IRAC Shallow Survey, of nearly 10,000 spectroscopically identified sources from the AGN and Galaxy Evolution Survey. On the basis of this spectroscopic sample, we find that simple mid-infrared color criteria provide remarkably robust separation of active galaxies from normal galaxies and Galactic stars, with over 80% completeness and less than 20% contamination. Considering only broad-lined AGNs, these mid-infrared color criteria identify over 90% of spectroscopically identified quasars and Seyfert 1 galaxies. Applying these color criteria to the full imaging data set, we discuss the implied surface density of AGNs and find evidence for a large population of optically obscured active galaxies.
TL;DR: In this paper, the authors analyzed a sample of ~2600 Spitzer MIPS 24 μm sources and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of the universe up to z ~ 1.
Abstract: We analyze a sample of ~2600 Spitzer MIPS 24 μm sources brighter than ~80 μJy and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of the universe up to z ~ 1. Using published ancillary optical data, we first obtain a nearly complete redshift determination for the 24 μm objects associated with R 24 mag counterparts at z 1. These sources represent ~55%-60% of the total MIPS 24 μm population with f24 μm 80 μJy, the rest of the sample likely lying at higher redshifts. We then determine an estimate of their total IR luminosities using various libraries of IR spectral energy distributions. We find that the 24 μm population at 0.5 z 1 is dominated by "luminous infrared galaxies" (i.e., 1011 L☉ ≤ LIR ≤ 1012 L☉), the counterparts of which appear to be also luminous at optical wavelengths and tend to be more massive than the majority of optically selected galaxies. A significant number of fainter sources (5 × 1010 L☉ LIR ≤ 1011 L☉) are also detected at similar distances. We finally derive 15 μm and total IR luminosity functions (LFs) up to z ~ 1. In agreement with the previous results from the Infrared Space Observatory (ISO) and SCUBA and as expected from the MIPS source number counts, we find very strong evolution of the contribution of the IR-selected population with look-back time. Pure evolution in density is firmly excluded by the data, but we find considerable degeneracy between strict evolution in luminosity and a combination of increases in both density and luminosity [L ∝ (1 + z), ∝ (1 + z)]. A significant steepening of the faint-end slope of the IR luminosity function is also unlikely, as it would overproduce the faint 24 μm source number counts. Our results imply that the comoving IR energy density of the universe evolves as (1 + z)3.9±0.4 up to z ~ 1 and that galaxies luminous in the infrared (i.e., LIR ≥ 1011 L☉) are responsible for 70% ± 15% of this energy density at z ~ 1. Taking into account the contribution of the UV luminosity evolving as (1 + z)~2.5, we infer that these IR-luminous sources dominate the star-forming activity beyond z ~ 0.7. The uncertainties affecting these conclusions are largely dominated by the errors in the k-corrections used to convert 24 μm fluxes into luminosities.
TL;DR: In this paper, a multwavelength submillimeter survey of 153 young stellar objects in the Taurus-Auriga star formation region is presented, with a detection rate of 61% to a completeness limit of 10 mJy (3 � ) at850� m.
Abstract: We present a sensitive, multiwavelength submillimeter continuum survey of 153 young stellar objects in the Taurus-Auriga star formation region. The submillimeter detection rate is 61% to a completeness limit of � 10 mJy (3 � )at850� m.Theinferredcircumstellardiskmassesarelognormallydistributedwithameanmassof � 5 ; 10 � 3 M� and a large dispersion (0.5 dex). Roughly one-third of the submillimeter sources have disk masses larger than the minimalnebulafromwhichthesolarsystemformed.Themediandisk-to-starmassratiois0.5%.Theempiricalbehavior of the submillimeter continuum is best described as F� / � 2:0� 0:5 between 350 � m and 1.3 mm, which we argue is duetothecombinedeffectsofthefractionofopticallythickemissionandaflatterfrequencybehavioroftheopacity compared to the interstellar medium. The latter effect could be due to a substantial population of large dust grains, which presumably would have grown through collisional agglomeration. In this sample, the only stellar property that is correlated with the outer disk is the presence of a companion. We find evidence for significant decreases in submillimeterfluxdensities,diskmasses,andsubmillimetercontinuumslopesalongthecanonicalinfraredspectral energy distribution evolution sequence for young stellar objects. The fraction of objects detected in the submillimeter isessentially identicalto the fractionwith excessnear-infrared emission,suggestingthatdustin the inner and outer disks is removed nearly simultaneously.
TL;DR: In this article, the authors investigated the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities.
Abstract: We reinvestigate the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of RBLR for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of RBLR for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data subsample and regression technique. Although small systematic differences were found depending on the method of analysis, our results are generally consistent. Assuming a power-law relation RBLR ∝ Lα, we find that the mean best-fitting α is about 0.67 ± 0.05 for the optical continuum and the broad Hβ luminosity, about 0.56 ± 0.05 for the UV continuum luminosity, and about 0.70 ± 0.14 for the X-ray luminosity. We also find an intrinsic scatter of ~40% in these relations. The disagreement of our results with the theoretical expected slope of 0.5 indicates that the simple assumption of all AGNs having on average the same ionization parameter, BLR density, column density, and ionizing spectral energy distribution is not valid and there is likely some evolution of a few of these characteristics along the luminosity scale.
University of Wisconsin-Madison1, University of Virginia2, Space Science Institute3, University of Maryland, College Park4, University of California, Berkeley5, Boston University6, University of Minnesota7, University of Wyoming8, European Space Research and Technology Centre9, California Institute of Technology10
TL;DR: In this paper, the extinction ratio between two of the filters, e.g., AJ/AK, is required to calculate A[λ]/AK from those measured ratios, which shows a flattening across the 3-8 μm wavelength range, roughly consistent with the extinction measurements derived by Lutz and coworkers for the sight line toward the Galactic center.
Abstract: We determine and tabulate A[λ]/AK, the wavelength dependence of interstellar extinction, in the Galactic plane for 1.25 μm ≤ λ ≤ 8.0 μm along two lines of sight: l = 42° and 284°. The first is a relatively quiescent and unremarkable region; the second contains the giant H II region RCW 49, as well as a "field" region unrelated to the cluster and nebulosity. Areas near these Galactic longitudes were imaged at J, H, and K bands by 2MASS and at 3-8 μm by Spitzer for the GLIMPSE Legacy program. We measure the mean values of the color excess ratios (A[λ] - AK)/(AJ - AK) directly from the color distributions of observed stars. The extinction ratio between two of the filters, e.g., AJ/AK, is required to calculate A[λ]/AK from those measured ratios. We use the apparent JHK magnitudes of giant stars along our two sight lines and fit the reddening as a function of magnitude (distance) to determine AJ kpc-1, AK kpc-1, and AJ/AK. Our values of A[λ]/AK show a flattening across the 3-8 μm wavelength range, roughly consistent with the extinction measurements derived by Lutz and coworkers for the sight line toward the Galactic center.
TL;DR: In this article, a complete sample of seven luminous early-type galaxies in the Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and 2.47 was reported.
Abstract: We report on a complete sample of seven luminous early-type galaxies in the Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and 2.47, and to KAB 1:4. Low-resolution spectra of these objects have been extracted from the Hubble Space Telescope (HST) ACS grism data taken over the UDF by the Grism ACS Program for Extragalactic Science (GRAPES) project. Redshifts for the seven galaxies have been identified based on the UV feature at rest frame 2640 < k < 2850 8. This feature is mainly due to a combination of Fe ii ,M gi ,a nd Mgii absorptions, which are characteristic of stellar populations dominated by stars older than � 0.5 Gyr. The redshift identification and the passively evolvingnatureofthesegalaxiesisfurthersupportedbythephotometricredshiftsandbytheoverallspectralenergy distribution (SED), with the ultradeep HST ACS NICMOS imaging revealing compact morphologies typical of
TL;DR: In this article, the authors used the ideal helical kink instability of a force-free coronal magnetic flux rope, anchored in the photosphere, as a model for solar eruptions.
Abstract: The ideal helical kink instability of a force-free coronal magnetic flux rope, anchored in the photosphere, is studied as a model for solar eruptions. Using the flux rope model of Titov and D?moulin as the initial condition in MHD simulations, both the development of helical shape and the rise profile of a confined (or failed) filament eruption (on 2002 May 27) are reproduced in very good agreement with the observations. By modifying the model such that the magnetic field decreases more rapidly with height above the flux rope, a full (or ejective) eruption of the rope is obtained in very good agreement with the developing helical shape and the exponential-to-linear rise profile of a fast coronal mass ejection (CME) on 2001 May 15. This confirms that the helical kink instability of a twisted magnetic flux rope can be the mechanism of the initiation and the initial driver of solar eruptions. The agreement of the simulations with properties that are characteristic of many eruptions suggests that they are often triggered by the kink instability. The decrease of the overlying field with height is a main factor in deciding whether the instability leads to a confined event or to a CME.
TL;DR: PHOEBE (PHysics of Eclipsing BinariEs) as discussed by the authors is a modeling package for eclipsing binary stars, built on top of the widely used WD program of Wilson & Devinney.
Abstract: PHOEBE (PHysics Of Eclipsing BinariEs) is a modeling package for eclipsing binary stars, built on top of the widely used WD program of Wilson & Devinney. This introductory paper gives an overview of the most important scientific extensions (incorporating observational spectra of eclipsing binaries into the solution-seeking process, extracting individual temperatures from observed color indices, main-sequence constraining, and proper treatment of the reddening), numerical innovations (suggested improvements to WD's differential corrections method, the new Nelder & Mead downhill simplex method), and technical aspects (back-end scripter structure, graphical user interface). While PHOEBE retains 100% WD compatibility, its add-ons are a powerful way to enhance WD by encompassing even more physics and solution reliability. The operability of all these extensions is demonstrated on a synthetic main-sequence test binary; applications to real data will be published in follow-up papers. PHOEBE is released under the GNU General Public License, which guarantees it to be free and open to anyone interested in joining in on future development.
TL;DR: In this paper, the results of the Sun in Time multiwavelength program (X-rays to UV) of solar analogs with ages covering 0.1-7 Gyr were reported.
Abstract: We report on the results of the Sun in Time multiwavelength program (X-rays to UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter goal, which has the ultimate purpose of providing the spectral irradiance evolution of solar-type stars to be used in the study and modeling of planetary atmospheres. The results from the Sun in Time program suggest that the coronal X-ray-EUV emissions of the young main-sequence Sun were ~100-1000 times stronger than those of the present Sun. Similarly, the transition region and chromospheric FUV-UV emissions of the young Sun are expected to be 20-60 and 10-20 times stronger, respectively, than at present. When we consider the integrated high-energy emission from 1 to 1200 A, the resulting relationship indicates that about 2.5 Gyr ago the solar high-energy flux was about 2.5 times the present value and about 3.5 Gyr ago was about 6 times the present value (when life supposedly arose on Earth). The strong radiation emissions inferred should have had major influences on the thermal structure, photochemistry, and photoionization of planetary atmospheres and have played an important role in the development of primitive life in the solar system. Some examples of the application of the Sun in Time results on exoplanets and on early solar system planets are discussed.
TL;DR: In this paper, the color transformation induced by star formation and active galactic nuclei during major mergers of spiral galaxies is studied. But the authors assume that a small fraction of the bolometric luminosity of an accreting black hole couples thermally to surrounding gas, providing a feedback mechanism that regulates its growth.
Abstract: We use hydrodynamical simulations to study the color transformations induced by star formation and active galactic nuclei (AGNs) during major mergers of spiral galaxies. Our modeling accounts for radiative cooling, star formation, and supernova feedback. Moreover, we include a treatment of accretion onto supermassive black holes embedded in the nuclei of the merging galaxies. We assume that a small fraction of the bolometric luminosity of an accreting black hole couples thermally to surrounding gas, providing a feedback mechanism that regulates its growth. The encounter and coalescence of the galaxies triggers nuclear gas inflow, which fuels both a powerful starburst and strong black hole accretion. Comparing simulations with and without black holes, we show that AGN feedback can quench star formation and accretion on a short timescale, particularly in large galaxies where the black holes can drive powerful winds once they become sufficiently massive. The color evolution of the remnant differs markedly between mergers with and without central black holes. Without AGNs, gas-rich mergers lead to elliptical galaxies that remain blue owing to residual star formation, even after more than 7 Gyr have elapsed. In contrast, mergers with black holes produce elliptical galaxies that redden much faster, an effect that is more pronounced in massive remnants where a nearly complete termination of star formation occurs, allowing them to redden to u - r 2.3 in less than 1 Gyr. AGN feedback may thus be required to explain the population of extremely red massive early-type galaxies, and it appears to be an important driver in generating the observed bimodal color distribution of galaxies in the local universe.
University of Arizona1, Ohio State University2, University of Chicago3, Fermilab4, New York University5, University of Pittsburgh6, Princeton University7, Nagoya University8, University of Tokyo9, University of Nottingham10, New Mexico State University11, University of Washington12, University of Sussex13, University of Edinburgh14, Pennsylvania State University15, University of Pennsylvania16, Drexel University17
TL;DR: In this article, the authors measured the projected correlation function wp(rp), which is directly related to the real-space correlation function, and interpreted these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters.
Abstract: Westudytheluminosityandcolordependenceofthegalaxytwo-pointcorrelationfunctionintheSloanDigitalSky Survey, starting from a sample of � 200,000 galaxies over 2500 deg 2 . We concentrate our analysis on volume-limited subsamples of specified luminosity ranges, for which we measure the projected correlation function wp(rp), which is directly related to the real-space correlation function � (r). The amplitude of wp(rp) rises continuously with luminosity from Mr �� 17: 5t oMr �� 22:5, with the most rapid increase occurring above the characteristic luminosity L� (Mr �� 20:5). Over the scales 0:1 h � 1 Mpc � 22 can be approximated, imperfectly, by power-law three-dimensional correlation functions � (r) ¼ (r/r0) � � with � � 1:8 and r0(L� ) � 5:0 h � 1 Mpc. The brightest subsample, � 23 < Mr < � 22, has a significantly steeper � (r). When we divide samples by color, redder galaxies exhibit a higher amplitude and steeper correlation function at all luminosities. The correlation amplitude of blue galaxies increases continuously with luminosity, but the luminosity dependence for red galaxies is less regular, with bright red galaxies exhibiting the strongest clustering at large scales and faint red galaxies exhibiting the strongest clustering at small scales. We interpret these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters. For most samples, an HOD model with two adjustable parameters fits the wp(rp) data better than a power law, explaining inflections at rp � 1 3 h � 1 Mpc as the transition between the one-halo and two-halo regimes of � (r). The implied minimum mass for a halo hosting a central galaxy more luminous than L grows steadily, with Mmin / L at low luminosities and a steeper dependence above L� . The mass at which a halo has, on average, one satellite galaxy brighter than L is M1 � 23Mmin(L), at all luminosities. These results imply a conditional luminosity function (at fixed halo mass) in which central galaxies lie far above a Schechter function extrapolation of the satellite population. The HOD model fits nicely explain the color dependence of wp(rp) and the cross correlation between red and blue galaxies. For galaxies with Mr < � 21, halos slightly above Mmin have blue central galaxies, while more massive halos have red central galaxies and predominantly red satellite populations. The fraction of blue central galaxies increases steadily with decreasing luminosity and host halo mass. The strong clustering offaint red galaxies follows from the fact that nearly all of them are satellite systems in high-mass halos. The HOD fitting results are in good qualitative agreement with the predictions of numerical and semianalytic models of galaxy formation. Subject headingg cosmology: observations — cosmology: theory — galaxies: distances and redshifts — galaxies: halos — galaxies: statistics — large-scale structure of universe
TL;DR: In this article, a diffraction-limited image of the galactic center was obtained with the W.M.KeckI10mtelescope, which was used to estimate the central dark mass of the galaxy.
Abstract: Wepresentnew diffraction-limitedimagesoftheGalacticcenter, obtainedwith theW.M.KeckI10mtelescope. Within0B4oftheGalaxy’scentraldarkmass,17proper-motionstars,withKmagnitudesrangingfrom 14.0to16.8, areidentified,and10ofthesearenewdetections(sixwerealsoindependentlydiscoveredbyothers).Inthissample, three newly identified (S0-16, S0-19, and S0-20) and four previously known (S0-1, S0-2, S0-4, and S0-5) sources have measured proper motions that reveal orbital solutions. Orbits are derived simultaneously so that they jointly constrain the central dark object’s properties: its mass,its position, and, for the first time using orbits, its motion on the plane of the sky. This analysis pinpoints the Galaxy’s central dark mass to within 1.3 mas (10 AU) and limits its propermotionto1:5 � 0:5masyr � 1 (orequivalently60 � 20kms � 1 )withrespecttothecentralstellarcluster.This localizationofthecentraldarkmassisconsistentwithourderivationofthepositionoftheradiosourceSgrA*inthe infrared reference frame (� 10 mas) but with an uncertainty that is a factor of 8 times smaller, which greatly facilitates searches for near-infrared counterparts to the central black hole. Consequently, one previous claim for such a counterpart can now be ascribed to a close stellar passage in 1996. Furthermore, we can place a conservative upper limit of 15.5 mag on any steady state counterpart emission. The estimated central dark mass from orbital motions is 3:7(� 0:2) ;10 6 R0= 8k pc ðÞ ½� 3 M� ; this is a more direct measure of mass than those obtained from velocitydispersion measurements,which are asmuchasafactorof2 smaller.The Galactic center’sdistance,which adds an additional 19% uncertainty in the estimated mass, is now the limiting source of uncertainty in the absolute mass. For stars in this sample, the closest approach is achieved by S0-16, which came within a mere 45 AU (=0:0002 pc ¼ 600Rs) at a velocity of 12,000 km s � 1 . This increases the inferred dark mass density by 4 orders of magnitude compared to earlier analyses based on velocity and acceleration vectors, making the Milky Way the strongest existing case for a supermassive black hole at the center of a normal-type galaxy. Well-determined orbital parameters for these seven Sgr A* cluster stars also provide new constraints on how these apparently massive, young (<10 Myr) stars formed in a region that seems to be hostile to star formation. Unlike the more distant He i emission line stars—another population of young stars in the Galactic center—that appear to have coplanar orbits, the Sgr A* cluster stars have orbital properties (eccentricities, angular momentum vectors, and apoapse directions) that are consistent with an isotropic distribution. Therefore, many of the mechanisms proposed for the formation of the He i stars, such as formation from a preexisting disk, are unlikely solutions for the Sgr A* cluster stars. Unfortunately, alternative theories for producing young stars, or old stars that look young, in close proximity to a centralsupermassiveblackholeareallalsosomewhatproblematic.Understandingtheapparentyouthofstarsinthe Sgr A* cluster, as well as the more distant Hei emission line stars, has now become one of the major outstanding issues in the study of the Galactic center. Subject headingg black hole physics — Galaxy: center — Galaxy: kinematics and dynamics — infrared: stars — techniques: high angular resolution
TL;DR: In this paper, the authors examined the contribution of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class.
Abstract: The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at the level of individual dark matter halos. The properties of galaxies residing at the centers of halos differ from those of satellite galaxies because of differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation and a semianalytic (SA) galaxy formation model, we examine the separate contributions of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class. In agreement with earlier results for dark matter subhalos, we find that the mean occupation function langNrangM for galaxies above a baryonic mass threshold can be approximated by a step function for central galaxies plus a power law for satellites and that the distribution of satellite numbers is close to Poisson at fixed halo mass. Since the number of central galaxies is always zero or one, the width of P(N|M) is narrower than a Poisson distribution at low N and approaches Poisson at high N. For galaxy samples defined by different baryonic mass thresholds, there is a nearly linear relation between the minimum halo mass Mmin required to host a central galaxy and the mass M1 at which an average halo hosts one satellite, with M1 ≈ 14Mmin (SPH) or M1 ≈ 18Mmin (SA). The stellar population age of central galaxies correlates with halo mass, and this correlation explains much of the age dependence of the galaxy HOD. The mean occupation number of young galaxies exhibits a local minimum at M ~ 10Mmin where halos are too massive to host a young central galaxy but not massive enough to host satellites. Using the SA model, we show that the conditional galaxy mass function at fixed halo mass cannot be described by a Schechter function because central galaxies produce a "bump" at high masses. We suggest parameterizations for the HOD and the conditional luminosity function that can be used to model observed galaxy clustering. Many of our predictions are in good agreement with recent results inferred from clustering in the Sloan Digital Sky Survey.
TL;DR: In this article, the authors present the first stellar evolution calculations to follow the evolution of rotating massive stars including, at least approximately, all these effects, magnetic and nonmagnetic, from the zero-age main sequence until the onset of iron-core collapse.
Abstract: As a massive star evolves through multiple stages of nuclear burning on its way to becoming a supernova, a complex, differentially rotating structure is set up. Angular momentum is transported by a variety of classic instabilities and also by magnetic torques from fields generated by the differential rotation. We present the first stellar evolution calculations to follow the evolution of rotating massive stars including, at least approximately, all these effects, magnetic and nonmagnetic, from the zero-age main sequence until the onset of iron-core collapse. The evolution and action of the magnetic fields is as described by Spruit in 2002, and a range of uncertain parameters is explored. In general, we find that magnetic torques decrease the final rotation rate of the collapsing iron core by about a factor of 30-50 when compared with the nonmagnetic counterparts. Angular momentum in that part of the presupernova star destined to become a neutron star is an increasing function of main-sequence mass. That is, pulsars derived from more massive stars rotate faster and rotation plays a more important role in the star's explosion. The final angular momentum of the core has been determined—to within a factor of 2—by the time the star ignites carbon burning. For the lighter stars studied, around 15 M☉, we predict pulsar periods at birth near 15 ms, though a factor of 2 range is easily tolerated by the uncertainties. Several mechanisms for additional braking in a young neutron star, especially by fallback, are explored.
TL;DR: In this paper, the authors consider the structure of marginally Toomre-stable starburst disks under the assumption that radiation pressure on dust grains provides the dominant vertical support against gravity.
Abstract: We consider the structure of marginally Toomre-stable starburst disks under the assumption that radiation pressure on dust grains provides the dominant vertical support against gravity. This assumption is particularly appropriate when the disk is optically thick to its own infrared radiation, as in the central regions of ULIRGs. We argue that because the disk radiates at its Eddington limit (for dust), the "Schmidt law" for star formation changes in the optically thick limit, with the star formation rate per unit area scaling as ∝ Σg/κ, where Σg is the gas surface density and κ is the mean opacity of the disk. Our calculations further show that optically thick starburst disks have a characteristic flux, star formation rate per unit area, and dust effective temperature of F ~ 1013 L☉ kpc-2, ~ 103 M☉ yr-1 kpc-2, and Teff ~ 90 K, respectively. We compare our model predictions with observations of ULIRGs and find good agreement. We extend our model of starburst disks from many hundred parsec scales to subparsec scales and address the problem of fueling AGNs. We assume that angular momentum transport proceeds via global torques (e.g., spiral waves, winds, or a central bar) rather than a local viscosity. We consistently account for the radial depletion of gas due to star formation and find a strong bifurcation between two classes of disk models: (1) solutions with a starburst on large scales that consumes all of the gas with little or no fueling of a central AGN and (2) models with an outer large-scale starburst accompanied by a more compact starburst on 1-10 pc scales and a bright central AGN. The luminosity of the latter models is in many cases dominated by the AGN, although these disk solutions exhibit a broad mid- to far-infrared peak from star formation. We show that the vertical thickness of the starburst disk on parsec scales can approach h ~ r, perhaps accounting for the nuclear obscuration in some type 2 AGNs. We also argue that the disk of young stars in the Galactic center may be the remnant of such a compact nuclear starburst.
TL;DR: In this paper, the authors present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1, which represents the first direct detection of photons emitted by a planet orbiting another star.
Abstract: We present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1. The data span a predicted time of secondary eclipse, corresponding to the passage of the planet behind the star. In both bands of our observations, we detect a flux decrement with a timing, amplitude, and duration as predicted by published parameters of the system. This signal represents the first direct detection of (i.e. the observation of photons emitted by) a planet orbiting another star. The observed eclipse depths (in units of relative flux) are 0.00066 ± 0.00013 at 4.5 µm and 0.00225±0.00036 at 8.0 µm. These estimates provide the first observational constraints on models of the thermal emission of hot Jupiters. Assuming that the planet emits as a blackbody, we estimate an effective temperature of Tp = 1060 ±50 K. Under the additional assumptions that the planet is in thermal equilibrium with the radiation from the star and emits isotropically, we find a Bond albedo of A = 0.31 ± 0.14. This would imply that the planet absorbs the majority of stellar radiation incident upon it, a conclusion of significant impact to atmospheric models of these objects. We also compare our data to a previously-published model of the planetary thermal emission, which predicts prominent spectral features in our observational bands due to water and carbon monoxide. This model adequately reproduces the observed planet-to-star flux ratio at 8.0 µm, however it significantly over-predicts the ratio at 4.5 µm. We also present an estimate of the timing of the secondary eclipse, which we use to place a
TL;DR: In this paper, the authors present a new method for estimating the masses of black holes in low-redshift active galaxies based on the width of the broad Hα emission line.
Abstract: It has been established that virial masses for black holes in low-redshift active galaxies can be estimated from measurements of the optical continuum strength and the width of the broad Hβ line. Under various circumstances, however, both of these quantities can be challenging to measure or can be subject to large systematic uncertainties. To mitigate these difficulties, we present a new method for estimating black hole masses. From analysis of a new sample of broad-line active galactic nuclei, we find that Hα luminosity scales almost linearly with optical continuum luminosity and that a strong correlation exists between Hα and Hβ line widths. These two empirical correlations allow us to translate the standard virial mass system to a new one based solely on observations of the broad Hα emission line.
TL;DR: In this article, the dependence of galactic outflow speeds on starburst luminosity and galactic mass has been investigated in 18 ultraluminous infrared galaxies (ULIGs) using Doppler shifts.
Abstract: Measurements of interstellar Na I λλ5890, 5896 absorption lines in 18 ultraluminous infrared galaxies (ULIGs) have been combined with published Na I data, to reassess the dependence of galactic outflow speeds on starburst luminosity and galactic mass. The Doppler shifts reveal outflows of relatively cool gas in 15 of 18 ULIGs with an average outflow speed at the line center of 330 ± 100 km s-1. The relation between outflow speed and star formation rate (SFR), defined by the distribution's upper envelope over 4 orders of magnitude in SFR, demonstrates that winds from more luminous starbursts accelerate interstellar gas to higher speeds roughly as v ∝ SFR0.35. This result is surprising since, in the traditional model for starburst-driven winds, these relatively cool gas clouds are accelerated by the ram pressure of a hot, supernova-heated wind that exhibits weak (if any) X-ray temperature variation with increasing galactic mass. The lack of evidence for much hotter winds is partly a sensitivity issue, but the Na I velocities in ultraluminous starbursts actually are consistent with acceleration by the tepid wind, indicating that a hotter component is unlikely to dominate the momentum flux. The Na I velocities in the dwarf starburst winds do not reach the terminal velocity of a hot wind at the measured temperature of kT ~ 0.73 keV, a result that could be interpreted simply as evidence that the hot superbubbles are too confined in dwarf starbursts to generate a free-flowing wind. A dynamically motivated scenario, however, is that the dwarf starburst winds simply lack enough momentum to accelerate the clouds to the velocity of the hot wind. Among the subsample of starbursts with well-constrained dynamical masses, the terminal outflow velocities are always found to approach the galactic escape velocity. Motivated by a similar scaling relation for stellar winds, the galactic Eddington luminosity for dusty starbursts is shown to be within the range measured for ULIGs. If radiation pressure on dust grains, coupled to the cool wind, is indeed important for galactic wind dynamics, then feedback is stronger in massive galaxies than previously thought, helping shape the high-mass end of the galaxy luminosity function. Regardless of the nature of the acceleration mechanism in ULIGs, the mass flux of cool gas estimated from these data demonstrates that starburst-driven winds transport significant gas during the assembly stage of field elliptical galaxies, a factor that helps explain the rapid decline in SFR in these systems inferred from elemental abundance ratios.
TL;DR: In this article, a 0.6-4.1?m spectroscopic sequence of M, L, and T dwarfs was presented, which nearly double the number of observed L and T-band spectra.
Abstract: We present a 0.6-4.1 ?m spectroscopic sequence of M, L, and T dwarfs. The spectra have R ? ?/?? ? 2000 from 0.9 to 2.4 ?m and R = 2500-200 from 2.9 to 4.1 ?m. These new data nearly double the number of L and T dwarfs that have reported L-band spectra. The near-infrared spectra are combined with previously published red-optical spectra to extend the wavelength coverage to ~0.6 ?m. Prominent atomic and molecular absorption features are identified including neutral lines of Al, Fe, Mg, Ca, Ti, Na, and K and 19 new weak CH4 absorption features in the H-band spectra of mid- to late-type T dwarfs. In addition, we detect for the first time the 0-0 band of the A 4?-X 4?- transition of VO at ~1.06 ?m in the spectra of L dwarfs and the P- and R-branches of the ?3 band of CH4 in the spectrum of a T dwarf. The equivalent widths of the refractory atomic features all decrease with increasing spectral type and are absent by a spectral type of ~L0, except for the 1.189 ?m Fe I line, which persists to at least ~L3. We compute the bolometric luminosities of the dwarfs in our sample with measured parallaxes and find good agreement with previously published results that use L'-band photometry to account for the flux emitted from 2.5 to 3.6 ?m. Finally, 2MASS J2224381-0158521 (L4.5) has an anomalously red spectrum and the strongest ?? = +2 CO bands in our sample. This may be indicative of unusually thick condensate clouds and/or low surface gravity.