- ID:
- ivo://CDS.VizieR/J/ApJ/843/41
- Title:
- HST/WFC3 obs. of z~2-8 galaxies in 4 HFF clusters
- Short Name:
- J/ApJ/843/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide the first observational constraints on the sizes of the faintest galaxies lensed by the Hubble Frontier Fields (HFF) clusters. Ionizing radiation from faint galaxies likely drives cosmic reionization, and the HFF initiative provides a key opportunity to find such galaxies. However, we cannot assess their ionizing emissivity without a robust measurement of their sizes, since this is key to quantifying both their prevalence and the faint- end slope to the UV luminosity function. Here we provide the first size constraints with two new techniques. The first utilizes the fact that the detectability of highly magnified galaxies as a function of shear is very dependent on a galaxy's size. Only the most compact galaxies remain detectable in high-shear regions (versus a larger detectable size range for low shear), a phenomenon we quantify using simulations. Remarkably, however, no correlation is found between the surface density of faint galaxies and the predicted shear, using 87 high-magnification ({mu}=10-100) z~2-8 galaxies seen behind the first four HFF clusters. This can only be the case if faint (~-15mag) galaxies have significantly smaller sizes than more luminous galaxies, i.e., <~30mas or 160-240pc. As a second size probe, we rotate and stack 26 faint high-magnification sources along the major shear axis. Less elongation is found even for objects with an intrinsic half-light radius of 10mas. Together, these results indicate that extremely faint z~2-8 galaxies have near point-source profiles (half-light radii <30mas and perhaps 5-10mas). These results suggest smaller completeness corrections and hence shallower faint-end slopes for the z~2-8 LFs than derived in some recent studies (by {Delta}{alpha}>~0.1-0.3).
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/810/42
- Title:
- Hydrogen RRL parameters of H II regions
- Short Name:
- J/ApJ/810/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H II regions are the ionized spheres surrounding high-mass stars. They are ideal targets for tracing Galactic structure because they are predominantly found in spiral arms and have high luminosities at infrared and radio wavelengths. In the Green Bank Telescope H II Region Discovery Survey (GBT HRDS), we found that >30% of first Galactic quadrant H II regions have multiple hydrogen radio recombination line (RRL) velocities, which makes determining their Galactic locations and physical properties impossible. Here we make additional GBT RRL observations to determine the discrete H II region velocity for all 117 multiple-velocity sources within 18{deg}<l<65{deg}. The multiple-velocity sources are concentrated in the zone 22{deg}<l<32{deg}, coinciding with the largest regions of massive star formation, which implies that the diffuse emission is caused by leaked ionizing photons. We combine our observations with analyses of the electron temperature, molecular gas, and carbon recombination lines to determine the source velocities for 103 discrete H II regions (88% of the sample). With the source velocities known, we resolve the kinematic distance ambiguity for 47 regions, and thus determine their heliocentric distances.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/102
- Title:
- I-band GALFIT analysis of luminous infrared galaxies
- Short Name:
- J/ApJ/768/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L_IR_>10^11.4^ L_{sun}_) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W "I-band" images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64+/-0.62 mag (1.8_-0.4_^+1.4^ L_1_^*^), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger advances. In contrast, the fraction of nuclear PSFs increases toward later merger stages and is highest in late-stage systems with a single nucleus. Thus, light from an active galactic nucleus or compact nuclear star cluster is more visible at I band as ULIRGs enter their latter stages of evolution. Finally, both GOALS elliptical hosts and nearby Sloan Digital Sky Survey (SDSS) ellipticals occupy the same part of the surface brightness versus half-light radius plot (i.e., the "Kormendy Relation") and have similar slopes, consistent with the possibility that the GOALS galaxies belong to the same parent population as the SDSS ellipticals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/3674
- Title:
- IC 348 circumstellar discs ALMA data
- Short Name:
- J/MNRAS/478/3674
- Date:
- 10 Dec 2021 00:10:52
- Publisher:
- CDS
- Description:
- We present a 1.3mm continuum survey of the young (2-3Myr) stellar cluster IC 348 that lies at a distance of 310pc and is dominated by low-mass stars (M*~0.1-0.6M_{sun}_). We observed 136 Class II sources (discs that are optically thick in the infrared) at 0.8arcsec (200au) resolution with a 3{sigma} sensitivity of ~0.45mJy (M_dust_~1.3M_{Earth}_). We detect 40 of the targets and construct a mm-continuum luminosity function. We compare the disc mass distribution in IC 348 to those of younger and older regions, taking into account the dependence on stellar mass. We find a clear evolution in disc masses from 1 to 5-10Myr. The disc masses in IC 348 are significantly lower than those in Taurus (1-3Myr) and Lupus (1-3Myr), similar to those of Chamaleon I, (2-3Myr) and {sigma} Ori (3-5Myr) and significantly higher than in Upper Scorpiusrpius (5-10Myr). About 20 discs in our sample (~5 percent of the cluster members) have estimated masses (dust+gas)>1M_Jup_ and hence might be the precursors of giant planets in the cluster. Some of the most massive discs include transition objects with inner opacity holes based on their infrared Spectral Energy Distribution (SEDs). From a stacking analysis of the 96 non-detections, we find that these discs have a typical dust mass of just <=0.4M_{Earth}_, even though the vast majority of their infrared SEDs remain optically thick and show little signs of evolution. Such low-mass discs may be the precursors of the small rocky planets found by Kepler around M-type stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/1796
- Title:
- IDEOS redshift catalogue
- Short Name:
- J/MNRAS/455/1796
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first of a series of papers on the Infrared Database of Extragalactic Observables from Spitzer (IDEOS). In this work, we describe the identification of optical counterparts of the infrared sources detected in Spitzer Infrared Spectrograph (IRS) observations and the acquisition and validation of redshifts. The IDEOS sample includes all the spectra from the Cornell Atlas of Spitzer/IRS Sources (CASSIS, Lebouteiller et al., 2011ApJS..196....8L, 2015ApJS..218...21L) of galaxies beyond the Local Group. Optical counterparts were identified from correlation of the extraction coordinates with the NASA Extragalactic Database (NED). To confirm the optical association and validate NED redshifts, we measure redshifts with unprecedented accuracy on the IRS spectra ({sigma}({Delta}z/(1+z))~0.0011) by using an improved version of the maximum combined pseudo-likelihood method (MCPL). We perform a multistage verification of redshifts that considers alternate NED redshifts, the MCPL redshift, and visual inspection of the IRS spectrum. The statistics is as follows: the IDEOS sample contains 3361 galaxies at redshift 0<z<6.42 (mean: 0.48, median: 0.14). We confirm the default NED redshift for 2429 sources and identify 124 with incorrect NED redshifts. We obtain IRS-based redshifts for 568 IDEOS sources without optical spectroscopic redshifts, including 228 with no previous redshift measurements. We provide the entire IDEOS redshift catalogue in machine-readable formats. The catalogue condenses our compilation and verification effort, and includes our final evaluation on the most likely redshift for each source, its origin, and reliability estimates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/346/1125
- Title:
- IK photometry of faint Extremely Red Objects
- Short Name:
- J/MNRAS/346/1125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a survey for extremely red objects (EROs) in deep, high-resolution optical images taken from the Hubble Space Telescope (HST) Medium Deep Survey. We have surveyed 35 deep F814W HST/WFPC2 fields in the near-infrared to a typical depth of K>20. From a total area of 206 arcmin^2^ and to a limit of K=20.0, we identify 224 EROs [(1.14+/-0.08)arcmin^-2^] with (I_814_-K)>=4.0 and 83 [(0.41+/-0.05)arcmin^-2^] with (I_814_-K)>=5.0.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/109
- Title:
- Imperial IRAS-FSC redshift catalogue (IIFSCz)
- Short Name:
- J/MNRAS/398/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue, the Imperial IRAS-FSC Redshift Catalogue (IIFSCz), of 60303 galaxies selected at 60um from the IRAS Faint Source Catalogue (FSC). The IIFSCz consists of accurate position, optical, near-infrared and/or radio identifications, spectroscopic redshift (if available) or photometric redshift (if possible), predicted far-infrared (FIR) and submillimetre (submm) fluxes ranging from 12 to 1380um based upon the best-fitting infrared template. About 55% of the galaxies in the IIFSCz have spectroscopic redshifts, and a further 20% have photometric redshifts obtained through either the training set or the template-fitting method. For S(60)>0.36Jy, the 90% completeness limit of the FSC, 90% of the sources have either spectroscopic or photometric redshifts. Scientific applications of the IIFSCz include validation of current and forthcoming infrared and submm/mm surveys such as AKARI, Planck and Herschel, follow-up studies of rare source populations, large-scale structure and galaxy bias, local multiwavelength luminosity functions and source counts. The catalogue is publicly available at http://astro.imperial.ac.uk/~mrr/fss/.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A44
- Title:
- Infrared dark cloud G28.3 HI and CI maps
- Short Name:
- J/A+A/638/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained. Identify and characterize the cloud formation signatures in atomic and molecular gas. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employ spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in ^13^CO in the 1-0 and 3-2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers, estimates of the mass flow rates, velocity structure functions, a Histogram of Oriented Gradients (HOG) study as well as comparisons to simulations. The central IRDC is embedded in a more diffuse envelope of cold neutral medium (CNM) traced by HI self-absorption (HISA) and molecular gas. The spectral line data as well as the HOG and structure function analysis indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and position-velocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent with gas flows being dominated by the formation of hierarchical structures. The observations and analysis are consistent with a picture where the IRDC G28 is formed at the center of two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar, gravitationally driven collapse of the cloud, external compression by, e.g., spiral arm shocks or supernovae explosions cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/343
- Title:
- Infrared excesses of Hipparcos stars
- Short Name:
- J/MNRAS/427/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the fundamental parameters (temperature and luminosity) of 107619 Hipparcos stars and place these stars on a true Hertzsprung-Russell diagram. This is achieved by comparing BT-SETTL model atmospheres to spectral energy distributions (SEDs) created from Hipparcos, Tycho, Sloan Digital Sky Survey, DENIS, Two Micron All Sky Survey, MSX, AKARI, IRAS and Wide-field Infrared Survey Explorer data. We also identify and quantify from these SEDs any infrared excesses attributable to circumstellar matter. We compare our results to known types of objects, focusing on the giant branch stars. Giant star dust production (as traced by infrared excess) is found to start in earnest around 680L_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/73
- Title:
- Infrared extinction toward the Galactic Centre
- Short Name:
- J/ApJ/737/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the extinction curve toward the Galactic center (GC) from 1 to 19um. We use hydrogen emission lines of the minispiral observed by ISO-SWS and SINFONI. The extinction-free flux reference is the 2cm continuum emission observed by the Very Large Array. Toward the inner 14"x20", we find an extinction of A_2.166um_=2.62+/-0.11, with a power-law slope of {alpha}=-2.11+/-0.06 shortward of 2.8um, consistent with the average near-infrared slope from the recent literature. At longer wavelengths, however, we find that the extinction is grayer than shortward of 2.8um. We find that it is not possible to fit the observed extinction curve with a dust model consisting of pure carbonaceous and silicate grains only, and the addition of composite particles, including ices, is needed to explain the observations. Combining a distance-dependent extinction with our distance-independent extinction, we derive the distance to the GC to be R_0_=7.94+/-0.65kpc. Toward Sgr A* (r<0.5"), we obtain A_H_=4.21+/-0.10, A_Ks_=2.42+/-0.10, and A_L'_=1.09+/-0.13.
