- ID:
- ivo://CDS.VizieR/J/MNRAS/472/4878
- Title:
- Number counts predictions for surveys
- Short Name:
- J/MNRAS/472/4878
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate the number counts of line emitters at high redshift and their evolution with cosmic time based on a combination of photometry and spectroscopy. We predict the H{alpha}, H{beta}, [OII], and [OIII] line fluxes for more than 35000 galaxies down to stellar masses of ~10^9^M_{sun}_ in the COSMOS and GOODS-S fields, applying standard conversions and exploiting the spectroscopic coverage of the FMOS-COSMOS survey at z~1.55 to calibrate the predictions. We calculate the number counts of H{alpha}, [OII], and [OIII] emitters down to fluxes of 1x10^-17^erg/cm^2^/s in the range 1.4<z<1.8 covered by the FMOS-COSMOS survey. We model the time evolution of the differential and cumulative H{alpha} counts, steeply declining at the brightest fluxes. We expect ~9300-9700 and ~2300-2900-galaxies/deg^2^ for fluxes >=1x10^-16^ and >=2x10^-16^erg/cm^2^/s over the range of 0.9<z<1.8. We show that the observed evolution of the main sequence of galaxies with redshift is enough to reproduce the observed counts variation at 0.2<z<2.5. We characterize the physical properties of the H{alpha} emitters with fluxes >=2x10^-16^erg/cm^2^/s including their stellar masses, UV sizes, [NII]/H{alpha} ratios and H{alpha} equivalent widths. An aperture of R~R_e_~0.5arcsec maximizes the signal-to-noise ratio for a detection, whilst causing a factor of ~2x flux losses, influencing the recoverable number counts, if neglected. Our approach, based on deep and large photometric data sets, reduces the uncertainties on the number counts due to the selection and spectroscopic samplings whilst exploring low fluxes. We publicly release the line flux predictions for the explored photometric samples.
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- ID:
- ivo://CDS.VizieR/J/ApJ/836/99
- Title:
- NuSTAR serendipitous survey: the 40-month catalog
- Short Name:
- J/ApJ/836/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ~20Ms of effective exposure time over 331 fields, with an areal coverage of 13deg^2^, and 497 sources detected in total over the 3-24keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z=0.002 to 3.4 (median of <z>=0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from log(f_3-24keV_/erg/s/cm^2^)~-14 to -11, and in rest-frame 10-40keV luminosity, from log(L_10-40keV_/erg/s)~39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ~15% at the highest luminosities (L_X_>10^44^erg/s) to ~80% at the lowest luminosities (L_X_<10^43^erg/s). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (i.e., the type 2 fraction) is F_Type2_=53_-15_^+14^% , for a well-defined subset of the 8-24keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10keV X-ray missions.
- ID:
- ivo://CDS.VizieR/J/ApJS/241/32
- Title:
- OB stars from the LAMOST DR5 spectra
- Short Name:
- J/ApJS/241/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 22901 OB spectra of 16032 stars identified from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope data release 5 (LAMOST DR5) data set. A larger sample of OB candidates are first selected from the distributions in the spectral line indices' space. Then, all 22901 OB spectra are identified by manual inspection. Based on a subsample validation, we find that the completeness of the OB spectra reaches about 89+/-22% for the stars with spectral types earlier than B7, while around 57+/-16% B8-B9 stars are identified. The smaller completeness for late B stars will lead to the difficulty in discriminating them from A0-A1-type stars. The subclasses of the OB samples are determined using the software package MKCLASS. With a careful validation using 646 subsamples, we find that MKCLASS can give fairly reliable subtypes and luminosity classes for most of the OB stars. The uncertainty of the spectral subtype is around 1 subtype, and the uncertainty of the luminosity class is around 1 level. However, about 40% of the OB stars fail to be assigned to any class by MKCLASS, and a few spectra are significantly misclassified by MKCLASS. This is likely because the template spectra of MKCLASS are selected from nearby stars in the solar neighborhood, while the OB stars in this work are mostly located in the outer disk and may have lower metallicities. The rotation of the OB stars may also be responsible for the misclassifications. Moreover, we find that the spectral and luminosity classes of the OB stars located in the Galactic latitude larger than 20{deg} are substantially different with those located in the latitude smaller than 20{deg}, which may either be due to the observational selection effect or may hint a different origin of the high Galactic latitude OB stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/205
- Title:
- [OII] emitting galaxies in the HETDEX survey
- Short Name:
- J/ApJ/799/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) pilot survey identified 284 [OII]{lambda}3727 emitting galaxies in a 169arcmin^2^ field of sky in the redshift range 0<z<0.57. This line flux limited sample provides a bridge between studies in the local universe and higher-redshift [OII] surveys. We present an analysis of the star formation rates (SFRs) of these galaxies as a function of stellar mass as determined via spectral energy distribution fitting. The [OII] emitters fall on the "main sequence" of star-forming galaxies with SFR decreasing at lower masses and redshifts. However, the slope of our relation is flatter than that found for most other samples, a result of the metallicity dependence of the [OII] star formation rate indicator. The mass-specific SFR is higher for lower mass objects, supporting the idea that massive galaxies formed more quickly and efficiently than their lower mass counterparts. This is confirmed by the fact that the equivalent widths of the [OII] emission lines trend smaller with larger stellar mass. Examination of the morphologies of the [OII] emitters reveals that their star formation is not a result of mergers, and the galaxies' half-light radii do not indicate evolution of physical sizes.
- ID:
- ivo://CDS.VizieR/J/AJ/106/591
- Title:
- OP Survey of Halo early-type stars
- Short Name:
- J/AJ/106/591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results are reported of an objective-prism survey of stars, mostly earlier than spectral type F5, for two fields at (l;b) = (90 deg and 270 deg; -45 deg). The fields, each of approximately 70 square degrees, are examined on plates taken with the Schmidt Telescope of the Anglo-Australian Observatory. The brightness range of the stars classified is 10 < V < 15. The prism combination used provides a dispersion of 600 A/mm at Hgamma. The spectral classification presented is defined by the equality of equivalent widths of Ca II K and Hdelta at type "F0" and the absence of Ca II K in stars with significant Balmer lines at type "A0". Positions listed in the catalog were measured on the Stromlo PDS microdensitometer. Most stars were subsequently identified with objects in the ST ScI-NASA-ESO Hubble Space Telescope Guide Star Catalog in which positions have an accuracy of near +/- 1.0 arcsec.
- ID:
- ivo://CDS.VizieR/J/AJ/144/16
- Title:
- Optical and HI properties of galaxies in voids
- Short Name:
- J/AJ/144/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the Sloan Digital Sky Survey. HI imaging of 55 galaxies with the Westerbork Synthesis Radio Telescope reveals morphological and kinematic signatures of ongoing interactions and gas accretion. We probe a total volume of 485Mpc^3^ within the voids, with an angular resolution of 8kpc at an average distance of 85Mpc. We reach column density sensitivities of 5x10^19^/cm^-2^, corresponding to an HI mass limit of 3x10^8^M_{sun}_. We detect HI in 41 galaxies, with total masses ranging from 1.7x10^8^ to 5.5x10^9^M_{sun}_. The upper limits on the 14 non-detections are not inconsistent with their luminosities, given their expected HI mass-to-light ratios. We find that the void galaxies are generally gas-rich, low-luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. The sample spans a range of absolute magnitudes (-16.1>M_r_>-20.4) and colors (0.06<g-r<0.87), and includes disk and irregular galaxies. We also identify three as early-type galaxies, all of which are not detected in HI. All galaxies have stellar masses less than 3x10^10^M_{sun}_, and many have kinematic and morphological signs of ongoing gas accretion, suggesting that the void galaxy population is still in the process of assembling. The small-scale clustering in the void, within 600kpc and 200km/s, is similar to that in higher density regions, and we identify 18 HI-rich neighboring galaxies in the voids. Most are within 100kpc and 100km/s of the targeted galaxy, and we find no significant population of HI-rich low-luminosity galaxies filling the voids, contrary to what is predicted by simulations.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/25
- Title:
- Optical properties of WISE galaxies
- Short Name:
- J/ApJ/758/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4deg^2^ region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22{mu}m selected galaxies. Among 507 WISE 22{mu}m selected sources with (S/N)_22{mu}m_>=3 ({approx}S_22{mu}m_>~2.5mJy), we identify the optical counterparts of 481 sources (~98%) at R<25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R<21 have SHELS spectroscopic data. Most of these objects are at z<0.8. The infrared (IR) luminosities are in the range 4.5x10^8^(L_{sun}_)<~L_IR_<~5.4x10^12^(L_{sun}_). Most 22{mu}m selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000{AA} break. The stacked spectra of the 22 {mu}m selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H{beta} grows with increasing IR luminosity. The optical spectra of the 22{mu}m selected galaxies also show that there are some (~2.8%) unusual galaxies with very strong [Ne III] {lambda}3869, 3968 emission lines that require hard ionizing radiation such as active galactic nuclei (AGNs) or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22{mu}m flux densities are enhanced if the 22{mu}m selected galaxies have close late-type neighbors. The sSFR distribution of the 22{mu}m selected galaxies containing AGNs is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy candidates with large (>~1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z~2.
- ID:
- ivo://CDS.VizieR/J/ApJ/624/135
- Title:
- Phoenix Deep Survey spectroscopic catalog
- Short Name:
- J/ApJ/624/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Phoenix Deep Survey is a multiwavelength survey based on deep 1.4GHz radio imaging, reaching well into the sub-100uJy level. One of the aims of this survey is to characterize the submillijansky radio population, exploring its nature and evolution. In this paper we present the catalog and results of the spectroscopic observations aimed at characterizing the optically "bright" (R<~21.5mag) counterparts of faint radio sources. Of 371 sources with redshift determination, 21% have absorption lines only, 11% show active galactic nucleus signatures, 32% are star-forming galaxies, 34% show narrow emission lines that do not allow detailed spectral classification (owing to poor signal-to-noise ratio and/or lack of diagnostic emission lines), and the remaining 2% are identified with stars.
- ID:
- ivo://CDS.VizieR/J/A+A/495/53
- Title:
- Physical properties of VVDS galaxies
- Short Name:
- J/A+A/495/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to derive the mass-metallicity relation of star-forming galaxies up to z~0.9, using data from the VIMOS VLT Deep Survey. The mass-metallicity relation is commonly understood as the relation between the stellar mass and the gas-phase oxygen abundance. Automatic measurement of emission-line fluxes and equivalent widths have been performed on the full spectroscopic sample of the VIMOS VLT Deep Survey. This sample is divided into two sub-samples depending on the apparent magnitude selection: wide (I_AB_<22.5) and deep (I_AB_<24). These two samples span two different ranges of stellar masses. Emission-line galaxies have been separated into star-forming galaxies and active galactic nuclei using emission line ratios. For the star-forming galaxies the emission line ratios have also been used to estimate gas-phase oxygen abundance, using empirical calibrations renormalized in order to give consistent results at low and high redshifts. The stellar masses have been estimated by fitting the whole spectral energy distributions with a set of stellar population synthesis models.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/11
- Title:
- PS1 z>5.6 quasars follow-up
- Short Name:
- J/ApJS/227/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminous quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far, these studies have been statistically limited by the number of quasars known at these redshifts. Such quasars are rare, and therefore, wide-field surveys are required to identify them, and multiwavelength data are required to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for the z~6 quasars presented in Banados+ (2014AJ....148...14B) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 quasars in the redshift range 5.6<~z<~6.7 that satisfy our selection criteria. Of these quasars, 77 have been discovered with PS1, and 63 of them are newly identified in this paper. We present the composite spectra of the PS1 distant quasar sample. This sample spans a factor of ~20 in luminosity and shows a variety of emission line properties. The number of quasars at z>5.6 presented in this work almost doubles the previously known quasars at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.