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871. Gas phase oxygen abundances for HII regions
ID:
ivo://CDS.VizieR/J/ApJ/887/80
Title:
Gas phase oxygen abundances for HII regions
Short Name:
J/ApJ/887/80
Date:
21 Oct 2021
Publisher:
CDS
Description:
The distribution of metals within a galaxy traces the baryon cycle and the buildup of galactic disks, but the detailed gas phase metallicity distribution remains poorly sampled. We have determined the gas phase oxygen abundances for 7138 HII regions across the disks of eight nearby galaxies using Very Large Telescope/Multi Unit Spectroscopic Explorer (MUSE) optical integral field spectroscopy as part of the PHANGS-MUSE survey. After removing the first-order radial gradients present in each galaxy, we look at the statistics of the metallicity offset ({Delta}O/H) and explore azimuthal variations. Across each galaxy, we find low ({sigma}=0.03-0.05dex) scatter at any given radius, indicative of efficient mixing. We compare physical parameters for those HII regions that are 1{sigma} outliers toward both enhanced and reduced abundances. Regions with enhanced abundances have high ionization parameter, higher H{alpha} luminosity, lower H{alpha} velocity dispersion, younger star clusters, and associated molecular gas clouds showing higher molecular gas densities. This indicates recent star formation has locally enriched the material. Regions with reduced abundances show increased H{alpha} velocity dispersions, suggestive of mixing introducing more pristine material. We observe subtle azimuthal variations in half of the sample, but cannot always cleanly associate this with the spiral pattern. Regions with enhanced and reduced abundances are found distributed throughout the disk, and in half of our galaxies we can identify subsections of spiral arms with clearly associated metallicity gradients. This suggests spiral arms play a role in organizing and mixing the interstellar medium.
872. GC hot UV-bright stars model spectra
ID:
ivo://CDS.VizieR/J/A+A/627/A34
Title:
GC hot UV-bright stars model spectra
Short Name:
J/A+A/627/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have performed a census of the UV-bright population in 78 globular clusters using wide-field UV telescopes. This population includes a variety of phases of post-horizontal branch (HB) evolution, including hot post-asymptotic giant branch (AGB) stars, and post-early AGB stars. There are indications that old stellar systems like globular clusters produce fewer post-(early) AGB stars than currently predicted by evolutionary models, but observations are still scarce. We wish to derive effective temperatures, surface gravities, and helium abundances of the luminous hot UV-bright stars in these clusters to determine their evolutionary status and compare the observed numbers to predictions from evolutionary theory. We obtained FORS2 spectroscopy of 11 of these UV-selected objects (covering a range of -2.3<[Fe/H]<-1.0), which we (re-)analysed together with previously observed data. We used model atmospheres of different metallicities, including super-solar ones. Where possible, we verified our atmospheric parameters using UV spectrophotometry and searched for metal lines in the optical spectra. We calculated evolutionary sequences for four metallicity regimes and used them together with information about the HB morphology of the globular clusters to estimate the expected numbers of post-AGB stars. We find that metal-rich model spectra are required to analyse stars hotter than 40000 K. Seven of the eleven new luminous UV-bright stars are post-AGB or post-early AGB stars, two are evolving away from the HB, one is a foreground white dwarf, and another is a white dwarf merger. Taking into account published information on other hot UV-bright stars in globular clusters, we find that the number of observed hot post-AGB stars generally agrees with the predicted values, although the numbers are still low. Spectroscopy is clearly required to identify the evolutionary status of hot UV-bright stars. For hotter stars, metal-rich model spectra are required to reproduce their optical and UV spectra, which may affect the flux contribution of hot post-AGB stars to the UV spectra of evolved populations. Adding published information on other hot UV-bright stars in globular clusters, we find that the number of observed hot post-AGB stars generally agrees with the predicted values, although the numbers are still low.
873. Gemini/FLAMINGOS-2 NIR spectra of V1047 Cen
ID:
ivo://CDS.VizieR/J/ApJ/886/L14
Title:
Gemini/FLAMINGOS-2 NIR spectra of V1047 Cen
Short Name:
J/ApJ/886/L14
Date:
21 Oct 2021
Publisher:
CDS
Description:
Fourteen years after its eruption as a classical nova (CN), V1047 Cen (Nova Cen 2005) began an unusual re-brightening in 2019 April. The amplitude of the brightening suggests that this is a dwarf nova (DN) eruption in a CN system. Very few CNe have had DN eruptions within decades of the main CN outburst. The 14yr separating the CN and DN eruptions of V1047 Cen is the shortest of all instances recorded thus far. Explaining this rapid succession of CN and DN outbursts in V1047 Cen may be challenging within the framework of standard theories for DN outbursts. Following a CN eruption, the mass accretion rate is believed to remain high (dM/dt~10^-8^M_{sun}_/yr) for a few centuries, due to the irradiation of the secondary star by the still-hot surface of the white dwarf. Thus a DN eruption is not expected to occur during this high mass accretion phase as DN outbursts, which result from thermal instabilities in the accretion disk, and arise during a regime of low mass accretion rate (dM/dt~10^-10^M_{sun}_/yr). Here we present near-infrared spectroscopy to show that the present outburst is most likely a DN eruption, and discuss the possible reasons for its early occurrence. Even if the present re-brightening is later shown to be due to a cause other than a DN outburst, the present study provides invaluable documentation of this unusual event.
874. Gemini/GMOS-S spectra of the type IIn SN 2010jl
ID:
ivo://CDS.VizieR/J/ApJ/894/111
Title:
Gemini/GMOS-S spectra of the type IIn SN 2010jl
Short Name:
J/ApJ/894/111
Date:
19 Jan 2022 13:05:54
Publisher:
CDS
Description:
The luminous Type IIn SN 2010jl shows strong signs of interaction between the SN ejecta and dense circumstellar material. Dust may be present in the unshocked ejecta; the cool, dense shell (CDS) between the shocks in the interaction region; or in the circumstellar medium (CSM). We present and model new optical and infrared photometry and spectroscopy of SN 2010jl from 82 to 1367 days since explosion. We evaluate the photometric and spectroscopic evolution using the radiative transfer codes MOCASSIN and DAMOCLES, respectively. We propose an interaction scenario and investigate the resulting dust formation scenarios and dust masses. We find that SN 2010jl has been continuously forming dust based on the evolution of its infrared emission and optical spectra. There is evidence for preexisting dust in the CSM as well as new dust formation in the CDS and/or ejecta. We estimate that 0.005-0.01M_{sun}_ of predominantly carbon dust grains has formed in SN 2010jl by ~1400 days post-outburst.
875. Gemini GNIRS NIR spectroscopy of 50 QSOs at z>~5.7
ID:
ivo://CDS.VizieR/J/ApJ/873/35
Title:
Gemini GNIRS NIR spectroscopy of 50 QSOs at z>~5.7
Short Name:
J/ApJ/873/35
Date:
19 Jan 2022 09:09:09
Publisher:
CDS
Description:
We report initial results from a large Gemini program to observe z>~5.7 quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with simultaneous ~0.85-2.5{mu}m spectra covering the rest-frame ultraviolet and major broad emission lines from Ly{alpha} to MgII. We present spectral measurements for these quasars and compare with their lower redshift counterparts at z=1.5-2.3. We find that when quasar luminosity is matched, there are no significant differences between the rest-UV spectra of z>~5.7 quasars and the low-z comparison sample. High-z quasars have similar continuum and emission line properties and occupy the same region in the black hole mass and luminosity space as the comparison sample, accreting at an average Eddington ratio of ~0.3. There is no evidence for super-Eddington accretion or hypermassive (>10^10^M_{sun}_) black holes within our sample. We find a mild excess of quasars with weak CIV lines relative to the control sample. Our results, corroborating earlier studies but with better statistics, demonstrate that these high-z quasars are already mature systems of accreting supermassive black holes operating with the same physical mechanisms as those at lower redshifts.
876. Gemini/HST GCP: galaxies in 4 massive clusters
ID:
ivo://CDS.VizieR/J/AJ/156/224
Title:
Gemini/HST GCP: galaxies in 4 massive clusters
Short Name:
J/AJ/156/224
Date:
21 Oct 2021
Publisher:
CDS
Description:
In order to study stellar populations and galaxy structures at intermediate and high redshift (z=0.2-2.0) and link these properties to those of low-redshift galaxies, there is a need for well-defined local reference samples. Especially for galaxies in massive clusters, such samples are often limited to the Coma cluster galaxies. We present consistently calibrated velocity dispersions and absorption-line indices for galaxies in the central 2 R_500_x2 R_500_ of four massive clusters at z<0.1: Abell 426/Perseus, Abell 1656/Coma, Abell 2029, and Abell 2142. The measurements are based on data from the Gemini Observatory, McDonald Observatory, and Sloan Digital Sky Survey. For bulge-dominated galaxies, the samples are 95% complete in Perseus and Coma and 74% complete in A2029 and A2142, to a limit of M_B,abs_=<-18.5 mag. The data serve as the local reference for our studies of galaxy populations in the higher-redshift clusters that are part of the Gemini/HST Galaxy Cluster Project (GCP). We establish the scaling relations between line indices and velocity dispersions as a reference for the GCP. We derive stellar population parameters, ages, metallicities [M/H], and abundance ratios from line indices, both averaged in bins of velocity dispersion and from individual measurements for galaxies in Perseus and Coma. The zero points of relations between the stellar population parameters and the velocity dispersions limit the allowed cluster-to-cluster variation of the four clusters to +/-0.08 dex in age, +/-0.06 dex in [M/H], +/-0.07 dex in [CN/Fe], and +/-0.03 dex in [Mg/Fe].
877. Gemini/NIFS and HST obs. of the galaxy M59-UCD3
ID:
ivo://CDS.VizieR/J/ApJ/858/102
Title:
Gemini/NIFS and HST obs. of the galaxy M59-UCD3
Short Name:
J/ApJ/858/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive-optics-assisted near-IR integral field spectroscopy from Gemini/NIFS and Hubble Space Telescope (HST) imaging. We use the multiband HST imaging to create a mass model that suggests and accounts for the presence of multiple stellar populations and structural components. We combine these mass models with kinematics measurements from Gemini/NIFS to find a best-fit stellar mass-to-light ratio (M/L) and black hole (BH) mass using Jeans anisotropic models (JAMs), axisymmetric Schwarzschild models, and triaxial Schwarzschild models. The best-fit parameters in the JAM and axisymmetric Schwarzschild models have BHs between 2.5 and 5.9 million solar masses. The triaxial Schwarzschild models point toward a similar BH mass but show a minimum {chi}^2^ at a BH mass of ~0. Models with a BH in all three techniques provide better fits to the central V_rms_ profiles, and thus we estimate the BH mass to be 4.2_-1.7_^+2.1^x10^6^M_{sun}_ (estimated 1{sigma} uncertainties). We also present deep radio imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass measurements, and we compare these to X-ray measurements to check for consistency with the fundamental plane of BH accretion. We detect faint radio emission in M59cO but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray detections in both these sources. The BH mass and nuclear light profile of M59-UCD3 suggest that it is the tidally stripped remnant of a ~10^9^-10^10^M_{sun}_ galaxy.
878. Gemini Planet Imager spectra of HR 8799 c/d/e
ID:
ivo://CDS.VizieR/J/AJ/155/226
Title:
Gemini Planet Imager spectra of HR 8799 c/d/e
Short Name:
J/AJ/155/226
Date:
21 Oct 2021
Publisher:
CDS
Description:
We explore Karhunen Loeve Image Projection (KLIP) forward modeling spectral extraction on Gemini Planet Imager coronagraphic data of HR 8799, using PyKLIP, and show algorithm stability with varying KLIP parameters. We report new and re-reduced spectrophotometry of HR 8799 c, d, and e in the H and K bands. We discuss a strategy for choosing optimal KLIP PSF subtraction parameters by injecting simulated sources and recovering them over a range of parameters. The K1/K2 spectra for HR 8799 c and d are similar to previously published results from the same data set. We also present a K-band spectrum of HR 8799 e for the first time and show that our H-band spectra agree well with previously published spectra from the VLT/SPHERE instrument. We show that HR 8799 c and d show significant differences in their H and K spectra, but do not find any conclusive differences between d and e, nor between c and e, likely due to large error bars in the recovered spectrum of e. Compared to M-, L-, and T-type field brown dwarfs, all three planets are most consistent with mid- and late-L spectral types. All objects are consistent with low gravity, but a lack of standard spectra for low gravity limit the ability to fit the best spectral type. We discuss how dedicated modeling efforts can better fit HR 8799 planets' near-IR flux, as well as how differences between the properties of these planets can be further explored.
879. Ghostly damped Ly{alpha} systems in SDSS DR14
ID:
ivo://CDS.VizieR/J/ApJ/901/123
Title:
Ghostly damped Ly{alpha} systems in SDSS DR14
Short Name:
J/ApJ/901/123
Date:
18 Feb 2022 09:18:37
Publisher:
CDS
Description:
We report the discovery of 59 new ghostly absorbers from the Sloan Digital Sky Survey Data Release 14. These absorbers, with z_abs_~z_QSO_, reveal no Ly{alpha} absorption, and they are mainly identified through the detection of strong metal absorption lines in the spectra. The number of such previously known systems is 30. The new systems are found with the aid of machine-learning algorithms. The spectra of 41 (out of total of 89) absorbers also cover the Ly{beta} spectral region. By fitting the damping wings of the Ly{beta} absorption in the stacked spectrum of 21 (out of 41) absorbers with relatively stronger Ly{beta} absorption, we measured an HI column density of log N(HI)=21.50. This column density is 0.5dex higher than that of the previous work. We also found that the metal absorption lines in the stacked spectrum of the 21 ghostly absorbers with stronger Ly{beta} absorption have similar properties as those in the stacked spectrum of the remaining systems. This circumstantial evidence strongly suggests that the majority of our ghostly absorbers are indeed DLAs.
880. Ghostly strong Lya absorbers in SDSS DR12
ID:
ivo://CDS.VizieR/J/ApJ/888/85
Title:
Ghostly strong Lya absorbers in SDSS DR12
Short Name:
J/ApJ/888/85
Date:
25 Oct 2021 10:15:53
Publisher:
CDS
Description:
We have searched the Sloan Digital Sky Survey Data Release 12 for ghostly strong Ly{alpha} (DLA) systems. These systems, located at the redshift of the quasars, show strong absorption from low-ionization atomic species but reveal no HI Ly{alpha} absorption. Our search has, for the first time, resulted in a sample of 30 homogeneously selected ghostly absorbers with z_QSO_>2.0. Thirteen of the ghostly absorbers exhibit absorption from other HI Lyman series lines. The lack of Ly{alpha} absorption in these absorbers is consistent with them being dense and compact with projected sizes smaller than the broad-line region of the background quasar. Although uncertain, the estimated median HI column density of these absorbers is logN(HI)~21.0. We compare the properties of ghostly absorbers with those of eclipsing DLAs that are high-column-density absorbers, located within 1500km/s of the quasar emission redshift and showing strong Ly{alpha} emission in their DLA trough. We discover an apparent sequence in the observed properties of these DLAs, with ghostly absorbers showing wider HI kinematics, stronger absorptions from high-ionization species, CII and SiII excited states, and a higher level of dust extinction. Since we estimate that all these absorbers have similar metallicities, logZ/Z_{sun}_~-1.0, we conclude that ghostly absorbers are part of the same population as eclipsing DLAs, except that they are denser and located closer to the central active galactic nuclei.

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