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1551. Massive star forming molecular clumps Tkin
ID:
ivo://CDS.VizieR/J/A+A/598/A30
Title:
Massive star forming molecular clumps Tkin
Short Name:
J/A+A/598/A30
Date:
21 Oct 2021
Publisher:
CDS
Description:
For a general understanding of the physics involved in the star formation process, measurements of physical parameters such as temperature and density are indispensable. The chemical and physical properties of dense clumps of molecular clouds are strongly affected by the kinetic temperature. Therefore, this parameter is essential for a better understanding of the interstellar medium. Formaldehyde, a molecule which traces the entire dense molecular gas, appears to be the most reliable tracer to directly measure the gas kinetic temperature.We aim to determine the kinetic temperature with spectral lines from formaldehyde and to compare the results with those obtained from ammonia lines for a large number of massive clumps.Three 218 GHz transitions (J_KAKC_=3_03_-2_02_, 3_22_-2_21_, and 3_21_-2_20_) of para-H_2_CO were observed with the 15m James Clerk Maxwell Telescope (JCMT) toward 30 massive clumps of the Galactic disk at various stages of high-mass star formation. Using the RADEX non-LTE model, we derive the gas kinetic temperature modeling the measured para-H_2_CO 3_22_-2_21_/3_03_-2_02_ and 3_21_-2_20_/3_03_-2_02_ ratios. The gas kinetic temperatures derived from the para-H2CO (3_21_-2_20_/3_03_-2_02_) line ratios range from 30 to 61K with an average of 46K. A comparison of kinetic temperature derived from para-H_2_CO, NH3, and the dust emission indicates that in many cases para-H_2_CO traces a similar kinetic temperature to the NH_3_ (2,2)/(1,1) transitions and the dust associated with the HII regions. Distinctly higher temperatures are probed by para-H_2_CO in the clumps associated with outflows/shocks. Kinetic temperatures obtained from para-H_2_CO trace turbulence to a higher degree than NH_3_ (2,2)/(1,1) in the massive clumps. The non-thermal velocity dispersions of para-H_2_CO lines are positively correlated with the gas kinetic temperature. The massive clumps are significantly influenced by supersonic non-thermal motions.
1552. Massive stars in APOGEE2 Survey. III.
ID:
ivo://CDS.VizieR/J/ApJS/247/17
Title:
Massive stars in APOGEE2 Survey. III.
Short Name:
J/ApJS/247/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have applied the semi-empirical spectral analysis, developed by the Sloan Digital Sky Survey (SDSS)-IV/Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE2) Massive Star Team, to a large sample of new O- and B-type stars identified along the Sagittarius spiral arm, in the direction of the southern star clusters NGC3603 and NGC3576. We obtained H-band spectra for 265 point sources, using the APOGEE2-S spectrograph at the du Pont Telescope at the Las Campanas Observatory. We analyzed the associated spectral features deriving spectral types, as well as the massive star distribution along the line of sight. From a total of 265 science targets, 95 are classified as mid- to late-O-type stars (for which only 10 O-type stars are previously known in the literature), 38 are found to be early- to mid-B-type stars, and 32 are classified as either yellow or blue supergiants, completing a total of 165 massive stars.
1553. 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.
1554. 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.
1555. 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.
1556. 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.
1557. 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.
1558. 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.
1559. 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.
1560. 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.

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