- ID:
- ivo://CDS.VizieR/J/ApJ/709/1257
- Title:
- Spitzer-IRS spectra of Seyfert galaxies. II.
- Short Name:
- J/ApJ/709/1257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our Spitzer-Infrared Spectrometer (IRS) spectroscopic survey from 10um to 37um of the Seyfert galaxies of the 12um Galaxy Sample (12MSG), collected in a high-resolution mode (R~600). The new spectra of 61 galaxies, together with the data we already published, give us a total of 91 12um Seyfert galaxies observed, out of 112. We discuss the mid-IR emission lines and features of the Seyfert galaxies, using an improved active galactic nucleus (AGN) classification scheme: instead of adopting the usual classes of Seyfert 1's and Seyfert 2's, we use the spectropolarimetric data from the literature to divide the objects into categories "AGN 1" and "AGN 2," where AGN 1's include all broad-line objects, including the Seyfert 2's showing hidden broad lines in polarized light. The remaining category, AGN 2's, contains only Seyferts with no detectable broad lines in either direct or polarized spectroscopy. We present various mid-IR observables, such as ionization-sensitive and density-sensitive line ratios, the polycyclic aromatic hydrocarbon (PAH) 11.25um feature and the H_2_S(1) rotational line equivalent widths (EWs), the (60-25um) spectral index, and the source extendedness at 19um, to characterize similarities and differences in the AGN populations, in terms of AGN dominance versus star formation dominance.
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- ID:
- ivo://CDS.VizieR/J/ApJS/208/24
- Title:
- Spitzer MIR AGN survey. I.
- Short Name:
- J/ApJS/208/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate active galactic nuclei (AGNs) selected in the mid-infrared. This survey selects both normal and obscured AGNs closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L _bol_~10^10^L_{sun}_ to highly luminous quasars (L_bol_~10^14^L_{sun}_), all with redshifts ranging from 0 to 4.3. Samples of candidate AGNs were selected with mid-infrared color cuts at several different 24{mu}m flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGNs and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type 1 AGNs with blue continua, 294 (44%) are type 2 objects with extinctions A_V_>~5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (A_V_~1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L_bol_>10^12^L_{sun}_, in the quasar regime. We present composite spectra for type 2 quasars and objects with no signs of AGN activity in their spectra. We also discuss the mid-infrared - emission-line luminosity correlation and present the results of cross correlations with serendipitous X-ray and radio sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/792/45
- Title:
- SPT-SZ survey galaxy clusters optical spectroscopy
- Short Name:
- J/ApJ/792/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical spectroscopy of galaxies in clusters detected through the Sunyaev-Zel'dovich (SZ) effect with the South Pole Telescope (SPT). We report our own measurements of 61 spectroscopic cluster redshifts, and 48 velocity dispersions each calculated with more than 15 member galaxies. This catalog also includes 19 dispersions of SPT-observed clusters previously reported in the literature. The majority of the clusters in this paper are SPT-discovered; of these, most have been previously reported in other SPT cluster catalogs, and five are reported here as SPT discoveries for the first time. By performing a resampling analysis of galaxy velocities, we find that unbiased velocity dispersions can be obtained from a relatively small number of member galaxies (<~ 30), but with increased systematic scatter. We use this analysis to determine statistical confidence intervals that include the effect of membership selection. We fit scaling relations between the observed cluster velocity dispersions and mass estimates from SZ and X-ray observables. In both cases, the results are consistent with the scaling relation between velocity dispersion and mass expected from dark-matter simulations. We measure a ~30% log-normal scatter in dispersion at fixed mass, and a ~10% offset in the normalization of the dispersion-mass relation when compared to the expectation from simulations, which is within the expected level of systematic uncertainty.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/57
- Title:
- Star formation activities in MaNGA low-mass galaxies
- Short Name:
- J/ApJ/894/57
- Date:
- 03 Dec 2021 00:39:35
- Publisher:
- CDS
- Description:
- We explore the environmental influences on the star formation (SF) in low-mass galaxies with stellar mass 8<=log(M_*_/M_{sun}_)<=10 at a redshift of 0.01<z<0.07. We identify the neighboring galaxies for our sample using the spectroscopically observed galaxies in the Sloan Digital Sky Survey (SDSS). Our 287 selected pair candidates have a neighboring galaxy with a stellar mass ratio of M_Neighbor_/M_Candidate_<=4 at a projected separation within d_proj_<=1500kpc and a line-of-sight kinematic separation of {Delta}v_LOS_<=300km/s. Our control galaxies are isolated from other galaxies within a projected radius of 1500kpc. All selected galaxies in our sample are spectroscopically observed by the fourth generation of SDSS/Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV/MaNGA) integral field spectroscopy survey. We radially bin our selected galaxies into three regions with a radial distance of 0<=R/R_e_<=0.5 (inner), 0.5<=R/R_e_<=1.0 (middle), and 1.0<=R/R_e_<=1.5 (outer), in which R_e_ is the effective radius at where the galaxy emit half of its light. We conclude that the SF activities in low-mass galaxies are affected by their environmental conditions when {Delta}v_LOS_<=100km/s at d_proj_<=400kpc. We use stellar-mass-weighted SF rate surface density ({Sigma}SFR/M_*_) to describe the SF strength in each radially binned region. For the pair candidates with 0.25<=M_Neighbor_/M_Candidate_<=4 at d_proj_<=100kpc and {Delta}v_LOS_<=100km/s, we observe an SF enhancement of f_{Delta}SF_=1.75+/-0.96 (f_{Delta}SF_=[({Sigma}SFR/M_*_)_Pair_-({Sigma}SFR/M_*_)_Control,mean_] /({Sigma}SFR/M_*_)_Control,mean_) in their inner regions, which decreases with increasing galactic radii.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/841
- Title:
- Star formation in E/S0 galaxies
- Short Name:
- J/ApJ/708/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent work has identified a population of low-redshift E/S0 galaxies that lie on the blue sequence in color versus stellar mass parameter space, where spiral galaxies typically reside. While high-mass blue-sequence E/S0s often resemble young merger or interaction remnants likely to fade to the red sequence, we focus on blue-sequence E/S0s with lower stellar masses (M_*_<a fewx10^10^M_{sun}_), which are characterized by fairly regular morphologies and low-density field environments where fresh gas infall is possible. This population may provide an evolutionary link between early-type galaxies and spirals through disk regrowth. Focusing on atomic gas reservoirs, we present new GBT HI data for 27 E/S0s on both sequences as well as a complete tabulation of archival HI data for other galaxies in the Nearby Field Galaxy Survey. Normalized to stellar mass, the atomic gas masses for 12 of the 14 blue-sequence E/S0s range from 0.1 to >1.0, demonstrating that morphological transformation is possible if the detected gas can be converted into stars. These gas-to-stellar mass ratios are comparable to those of spiral and irregular galaxies and have a similar dependence on stellar mass.
- ID:
- ivo://CDS.VizieR/J/ApJS/153/523
- Title:
- Starless cores in CS(3-2) and DCO^+^(2-1) lines
- Short Name:
- J/ApJS/153/523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CS(3-2) and DCO^+^(2-1) observations of 94 starless cores and compare the results with previous CS(2-1) and N_2_H^+^(1-0) observations to study inward motions in starless cores. Eighty-four cores were detected in both CS and DCO^+^ lines. We identify 18 infall candidates based on observations of CS(3-2), CS(2-1), DCO^+^(2-1) and N_2_H^+^(1-0). The eight best candidates, L1355, L1498, L1521F, L1544, L158, L492, L694-2, and L1155C-1, each show at least four indications of infall asymmetry and no counterindications. Fits of the spectra to a two-layer radiative transfer model in ten infall candidates suggest that the median effective line of sight speed of the inward-moving gas is ~0.07km/s for CS(3-2) and ~0.04km/s for CS(2-1).
- ID:
- ivo://CDS.VizieR/J/ApJ/891/23
- Title:
- Stellar abundances from LAMOST MRS (SPCAnet)
- Short Name:
- J/ApJ/891/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fundamental stellar atmospheric parameters (Teff and logg) and 13 chemical abundances are derived for medium-resolution spectroscopy from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Medium Resolution Survey (MRS) data sets with a deep-learning method. The neural networks we designed, named SPCANet, precisely map LAMOST MRS spectra to stellar parameters and chemical abundances. The stellar labels derived by SPCANet have precisions of 119K for Teff and 0.17dex for logg. The abundance precision of 11 elements including [C/H], [N/H], [O/H], [Mg/H], [Al/H], [Si/H], [S/H], [Ca/H], [Ti/H], [Cr/H], [Fe/H], and [Ni/H] are 0.06 {\sim} 0.12 dex, while that of [Cu/H] is 0.19dex. These precisions can be reached even for spectra with signal-to-noise ratios as low as 10. The results of SPCANet are consistent with those from other surveys such as APOGEE, GALAH, and RAVE, and are also validated with the previous literature values including clusters and field stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/15
- Title:
- Stellar mass-metallicity relation. I.
- Short Name:
- J/ApJ/856/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar mass-stellar metallicity relationship (MZR) in the galaxy cluster Cl0024+1654 at z~0.4 using full-spectrum stellar population synthesis modeling of individual quiescent galaxies. The lower limit of our stellar mass range is M*=10^9.7^M_{sun}_, the lowest galaxy mass at which individual stellar metallicity has been measured beyond the local universe. We report a detection of an evolution of the stellar MZR with observed redshift at 0.037+/-0.007dex per Gyr, consistent with the predictions from hydrodynamical simulations. Additionally, we find that the evolution of the stellar MZR with observed redshift can be explained by an evolution of the stellar MZR with the formation time of galaxies, i.e., when the single stellar population (SSP)-equivalent ages of galaxies are taken into account. This behavior is consistent with stars forming out of gas that also has an MZR with a normalization that decreases with redshift. Lastly, we find that over the observed mass range, the MZR can be described by a linear function with a shallow slope ([Fe/H]{propto}(0.16+/-0.03)logM*). The slope suggests that galaxy feedback, in terms of mass-loading factor, might be mass-independent over the observed mass and redshift range.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/62
- Title:
- Stellar parameters from the 1st release of the MaSTar
- Short Name:
- J/ApJ/899/62
- Date:
- 14 Mar 2022 07:12:49
- Publisher:
- CDS
- Description:
- We report the stellar atmospheric parameters for 7503 spectra contained in the first release of the Mapping Nearby Galaxies at Apache Point Observatory survey (MaNGA) stellar library (MaStar) in Sloan Digital Sky Survey DR15. The first release of MaStar contains 8646 spectra measured from 3321 unique stars, each covering the wavelength range 3622-10354{AA} with a resolving power of R~1800. In this work, we first determined the basic stellar parameters: effective temperature (Teff), surface gravity (logg), and metallicity ([Fe/H]), which best fit the data using an empirical interpolator based on the Medium-resolution Isaac Newton Telescope library of empirical spectra (MILES), as implemented by the University of Lyon Spectroscopic analysis Software package. While we analyzed all 8646 spectra from the first release of MaStar, since MaStar has a wider parameter-space coverage than MILES, not all of these fits are robust. In addition, not all parameter regions covered by MILES yield robust results, likely due to the nonuniform coverage of the parameter space by MILES. We tested the robustness of the method using the MILES spectra itself and identified a proxy based on the local density of the training set. With this proxy, we identified 7503 MaStar spectra with robust fitting results. They cover the range from 3179 to 20517K in effective temperature (Teff), from 0.40 to 5.0 in surface gravity (logg), and from -2.49 to +0.73 in metallicity ([Fe/H]).
- ID:
- ivo://CDS.VizieR/J/ApJ/739/L44
- Title:
- Structural data for galaxies between 0.2<z<2.7
- Short Name:
- J/ApJ/739/L44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the size growth seen in early-type galaxies over 10Gyr of cosmic time. Our analysis is based on a homogeneous synthesis of published data from 16 spectroscopic surveys observed at similar spatial resolution, augmented by new measurements for galaxies in the Gemini Deep Deep Survey. In total, our sample contains structural data for 465 galaxies (mainly early-type) in the redshift range 0.2<z<2.7. The size evolution of passively evolving galaxies over this redshift range is gradual and continuous, with no evidence for an end or change to the process around z~1, as has been hinted at by some surveys which analyze subsets of the data in isolation. The size growth appears to be independent of stellar mass, with the mass-normalized half-light radius scaling with redshift as R_e_{propto}(1+z)^-1.62+/-0.34^. Surprisingly, this power law seems to be in good agreement with the recently reported continuous size evolution of UV-bright galaxies in the redshift range z~0.5-3.5. It is also in accordance with the predictions from recent theoretical models.