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1541. Massive stars in SDSS/APOGEE-2. II. W3-W4-W5
ID:
ivo://CDS.VizieR/J/ApJ/873/66
Title:
Massive stars in SDSS/APOGEE-2. II. W3-W4-W5
Short Name:
J/ApJ/873/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we have applied a semi-empirical spectral classification method for OB-stars using the APOGEE spectrograph to a sample of candidates in the W3-W4-W5 (W345) complexes. These massive star-forming regions span over 200pc across the Perseus arm and have a notorious population of massive stars, from which a large fraction are members of various embedded and young open clusters. From 288 APOGEE spectra showing H-band spectral features typical of O- and B-type sources, 46 probably correspond to previously unknown O-type stars. Therefore, we confirm that Br11-Br13 together with HeII {lambda}16923 (7-12) and HeII {lambda}15723 (7-13) lines contained in the APOGEE spectral bands are useful in providing spectral classification down to one spectral sub-class for massive stars in regions as distant as d~2kpc. The large number of newly found O-type stars as well as the numerous intermediate-mass population confirm that W345 is a very efficient massive star factory, with an integral stellar population probably amounting several thousand solar masses.
1542. Massive stars in the SDSS-IV/APOGEE SURVEY. I.
ID:
ivo://CDS.VizieR/J/ApJ/855/68
Title:
Massive stars in the SDSS-IV/APOGEE SURVEY. I.
Short Name:
J/ApJ/855/68
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we make use of DR14 APOGEE spectroscopic data to study a sample of 92 known OB stars. We developed a near-infrared semi-empirical spectral classification method that was successfully used in case of four new exemplars, previously classified as later B-type stars. Our results agree well with those determined independently from ECHELLE optical spectra, being in line with the spectral types derived from the "canonical" MK blue optical system. This confirms that the APOGEE spectrograph can also be used as a powerful tool in surveys aiming to unveil and study a large number of moderately and highly obscured OB stars still hidden in the Galaxy.
1543. MASSIVE survey. XII. Early-type galaxy gradients
ID:
ivo://CDS.VizieR/J/ApJ/874/66
Title:
MASSIVE survey. XII. Early-type galaxy gradients
Short Name:
J/ApJ/874/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We measure the stellar populations as a function of the radius for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with an absolute K-band magnitude of M_K_{<}-25.3mag or a stellar mass of M_*_>~4x10^11^M_{sun}_, within 108Mpc. We are able to measure reliable stellar population parameters for individual galaxies out to 10-20kpc (1-3R_e_) depending on the galaxy. Focusing on ~R_e_ (~10kpc), we find significant correlations between the abundance ratios, {sigma}, and M^*^ at a large radius, but we also find that the abundance ratios saturate in the highest-mass bin. We see a strong correlation between the kurtosis of the line-of-sight velocity distribution (h4) and the stellar population parameters beyond R_e_. Galaxies with higher radial anisotropy appear to be older, with metal-poorer stars and enhanced [{alpha}/Fe]. We suggest that the higher radial anisotropy may derive from more accretion of small satellites. Finally, we see some evidence for correlations between environmental metrics (measured locally and on >5Mpc scales) and the stellar populations, as expected if satellites are quenched earlier in denser environments.
1544. Massive SZE clusters observations with ACT
ID:
ivo://CDS.VizieR/J/ApJ/772/25
Title:
Massive SZE clusters observations with ACT
Short Name:
J/ApJ/772/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455deg^2^ area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R~700-800) spectra and redshifts for {approx}60 member galaxies on average per cluster. The dynamical masses M_200c_ of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z=0.50 and a median mass M_200c_~12x10^14^h_70_^-1^M_{sun}_ with a lower limit M_200c_~6x10^14^h_70_^-1^M_{sun}_, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the match-filtered central SZE amplitude {overline}{y_0_}, the central Compton parameter y_0_, and the integrated Compton signal Y_200c_, which we use to derive SZE-mass scaling relations. All SZE estimators correlate with dynamical mass with low intrinsic scatter (<~20%), in agreement with numerical simulations. We explore the effects of various systematic effects on these scaling relations, including the correlation between observables and the influence of dynamically disturbed clusters. Using the three-dimensional information available, we divide the sample into relaxed and disturbed clusters and find that ~50% of the clusters are disturbed. There are hints that disturbed systems might bias the scaling relations, but given the current sample sizes, these differences are not significant; further studies including more clusters are required to assess the impact of these clusters on the scaling relations.
1545. Massive young stellar objects in 30 Doradus
ID:
ivo://CDS.VizieR/J/A+A/636/A54
Title:
Massive young stellar objects in 30 Doradus
Short Name:
J/A+A/636/A54
Date:
21 Oct 2021
Publisher:
CDS
Description:
The process of massive star (M>=8M_{sun}_) formation is still poorly understood. Observations of massive young stellar objects (MYSOs) are challenging due to their rarity, short formation timescale, large distances, and high circumstellar extinction. Here, we present the results of a spectroscopic analysis of a population of MYSOs in the Large Magellanic Cloud (LMC). We took advantage of the spectral resolution and wavelength coverage of X-shooter (300-2500nm), which is mounted on the European Southern Observatory Very Large Telescope, to detect characteristic spectral features in a dozen MYSO candidates near 30 Doradus, the largest starburst region in the Local Group hosting the most massive stars known. The X-shooter spectra are strongly contaminated by nebular emission. We used a scaling method to subtract the nebular contamination from our objects. We detect H{alpha},{beta}, [OI] 630.0nm, CaII infrared triplet, [FeII] 1643.5nm, fluorescent FeII 1687.8nm, H_2_ 2121.8nm, Br{gamma}, and CO bandhead emission in the spectra of multiple candidates. This leads to the spectroscopic confirmation of ten candidates as bona fide MYSOs. We compared our observations with photometric observations from the literature and find all MYSOs to have a strong near-infrared excess. We computed lower limits to the brightness and luminosity of the MYSO candidates, confirming the near-infrared excess and the massive nature of the objects. No clear correlation is seen between the Br_gamma luminosity and metallicity. Combining our sample with other LMC samples results in a combined detection rate of disk features such as fluorescent Fe II and CO bandheads which is consistent with the Galactic rate (40%). Most of our MYSOs show outflow features.
1546. Massive YSOs VLTI observations
ID:
ivo://CDS.VizieR/J/A+A/654/A109
Title:
Massive YSOs VLTI observations
Short Name:
J/A+A/654/A109
Date:
22 Feb 2022
Publisher:
CDS
Description:
Circumstellar discs are essential for high mass star formation, while multiplicity, in particular binarity, appears to be an inevitable outcome since the vast majority of massive stars (>8M_{sun}_) are found in binaries (up to 100%). We spatially resolve and constrain the sizes of the dust and ionised gas emission of the innermost regions towards a sample of MYSOs for the first time, and provide high-mass binary statistics of young stars at 2-300au scales. We observe six MYSOs with VLTI (GRAVITY, AMBER), to resolve and characterise the 2.2um hot dust emission originating from the inner rim of circumstellar discs around MYSOs, and the associated Br{gamma} emission from ionised gas. We fit simple geometrical models to the interferometric observables, and determine the inner radius of the dust emission. We place MYSOs with K-band measurements in a size-luminosity diagram for the first time, and compare our findings to T Tauris and Herbig AeBes. We also compare the observed K-band sizes to the sublimation radius predicted by three different disc scenarios. Lastly, we apply binary geometries to trace close binarity among MYSOs. When the inner sizes of MYSOs are compared to those of lower mass Herbig AeBe and T Tauri stars, they appear to follow a universal trend at which the sizes scale with the square-root of the stellar luminosity. The Br{gamma} emission originates from a similar or somewhat smaller and co-planar area compared to the 2.2um continuum emission. We discuss this new finding with respect to disc-wind or jet origin. Finally, we report an MYSO binary fraction of 17-25% at milli-arcsecond separations (2-300au). The size-luminosity diagram indicates that the inner regions of discs around young stars scale with luminosity independently of the stellar mass. At the targeted scales (2-300au), the MYSO binary fraction is lower than what was previously reported for the more evolved main sequence massive stars, which, if further confirmed, could implicate the predictions from massive binary formation theories. Lastly, we spatially resolve the crucial star/disc interface in a sample of MYSOs, showing that au-scale discs are prominent in high-mass star formation and similar to their low-mass equivalents.
1547. 2MASS J15111324-2130030 metal-poor star abundances
ID:
ivo://CDS.VizieR/J/ApJ/850/179
Title:
2MASS J15111324-2130030 metal-poor star abundances
Short Name:
J/ApJ/850/179
Date:
21 Oct 2021
Publisher:
CDS
Description:
The rapid neutron-capture or r-process is thought to produce the majority of the heavy elements (Z>30) in extremely metal-poor stars. The same process is also responsible for a significant fraction of the heavy elements in the Sun. This universality of the r-process is one of its characteristic features, as well as one of the most important clues to its astrophysical origin. We report the discovery of an extremely metal-poor field giant with [Sr,Ba/H]~-6.0 and [Sr,Ba/Fe]~-3.0, the lowest abundances of strontium and barium relative to iron ever observed. Despite its low abundances, the star 2MASS J151113.24-213003.0 has [Sr/Ba]=-0.11+/-0.14, therefore its neutron-capture abundances are consistent with the main solar r-process pattern that has [Sr/Ba]=-0.25. It has been suggested that extremely low neutron-capture abundances are a characteristic of dwarf galaxies, and we find that this star is on a highly eccentric orbit with an apocenter >~100kpc that lies in the disk of satellites in the halo of the Milky Way. We show that other extremely metal-poor stars with low [Sr,Ba/H] and [Sr,Ba/Fe] plus solar [Sr/Ba] tend to have orbits with large apocenters, consistent with a dwarf galaxy origin for this class of object. The nucleosynthesis event that produced the neutron-capture elements in 2MASS J151113.24-213003.0 must produce both strontium and barium together in the solar ratio. We exclude contributions from the s-process in intermediate-mass asymptotic giant branch or fast-rotating massive metal-poor stars, pair-instability supernovae, the weak r-process, and neutron-star mergers. We argue that the event was a Pop III or extreme Pop II core-collapse supernova explosion.
1548. 2MASS J22560844+5954299 spectra
ID:
ivo://CDS.VizieR/J/A+A/584/A40
Title:
2MASS J22560844+5954299 spectra
Short Name:
J/A+A/584/A40
Date:
21 Oct 2021
Publisher:
CDS
Description:
The SW Sex stars are assumed to represent a distinguished stage in CV evolution, making it especially important to study them. We discovered a new cataclysmic star and carried out prolonged and precise photometric observations, as well as medium- resolution spectral observations. Modelling these data allowed us to determine the physical parameters and to establish its peculiarities. To obtain a light curve solution we used model whose emission sources are a white dwarf surrounded by an accretion disk with a hot spot, a gaseous stream near the disk's lateral side, and a secondary star filling its Roche lobe. The obtained physical parameters are compared with those of other SW Sex-subtype stars.
1549. 2MASS J04183483+2131275 spectrum
ID:
ivo://CDS.VizieR/J/A+A/615/L12
Title:
2MASS J04183483+2131275 spectrum
Short Name:
J/A+A/615/L12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used the 10.4-m Gran Telescopio Canarias (GTC) with its low-dispersion optical spectrograph to obtain 10 spectra of 2277s each covering the range 6300-10300 Angstroms with a resolving power of R~500 for the Hyades brown dwarf 2MASSJ04183483+2131275. We detect lithium in absorption and Halpha in emission in this combined spectrum.
1550. Mass, Z, dust attenuation, and SFR relations
ID:
ivo://CDS.VizieR/J/ApJ/847/18
Title:
Mass, Z, dust attenuation, and SFR relations
Short Name:
J/ApJ/847/18
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass-star formation rate and the stellar mass-gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass-stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

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