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2951. Close visual companions in Scorpius OB2
ID:
ivo://CDS.VizieR/J/A+A/430/137
Title:
Close visual companions in Scorpius OB2
Short Name:
J/A+A/430/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a near-infrared adaptive optics survey with the aim to detect close companions to Hipparcos members in the three subgroups of the nearby OB association Sco OB2: Upper Scorpius (US), Upper Centaurus Lupus (UCL) and Lower Centaurus Crux (LCC). We have targeted 199 A-type and late B-type stars in the K_S band, and a subset also in the J and H band. We find 151 stellar components other than the target stars. A brightness criterion is used to separate these components into 77 background stars and 74 candidate physical companion stars. Out of these 74 candidate companions, 41 have not been reported before (14 in US; 13 in UCL; 14 in LCC).
2952. Close white dwarf + M dwarf binaries (WD+dM)
ID:
ivo://CDS.VizieR/J/AJ/144/93
Title:
Close white dwarf + M dwarf binaries (WD+dM)
Short Name:
J/AJ/144/93
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types <=M7. Our results show that early-type M dwarfs (<=M4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems become more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully convective stars. Using the WD components of the pairs, we find WD cooling ages to use as an additional constraint on the age-activity relation for our sample. We find that, on average, active early-type dMs tend to be younger and that active late-type dMs span a much broader age regime making them indistinguishable from the inactive late-type population. We also show that magnetic strength, as measured by H{alpha}, is comparable between paired and field M dwarfs until a spectral type of M6/M7 where M dwarf activity for stars with close companions becomes much stronger. In addition, we present 37 very close candidate pairs with fast-moving orbits that display radial velocity changes over hour timescales.
2953. Cloud Atlas: HST/WFC3 NIR spectral library
ID:
ivo://CDS.VizieR/J/AJ/157/101
Title:
Cloud Atlas: HST/WFC3 NIR spectral library
Short Name:
J/AJ/157/101
Date:
21 Oct 2021
Publisher:
CDS
Description:
Bayesian atmospheric retrieval tools can place constraints on the properties of brown dwarfs' and hot Jupiters' atmospheres. To fully exploit these methods, high signal-to-noise spectral libraries with well-understood uncertainties are essential. We present a high signal-to-noise spectral library (1.10-1.69 {mu}m) of the thermal emission of 76 brown dwarfs and hot Jupiters. All our spectra have been acquired with the Hubble Space Telescope's Wide Field Camera 3 instrument and its G141 grism. The near-infrared spectral types of these objects range from L4 to Y1. Eight of our targets have estimated masses below the deuterium-burning limit. We analyze the database to identify peculiar objects and/or multiple systems, concluding that this sample includes two very-low-surface-gravity objects and five intermediate-surface-gravity objects. In addition, spectral indices designed to search for composite-atmosphere brown dwarfs indicate that eight objects in our sample are strong candidates to have such atmospheres. None of these objects are overluminous, so their composite atmospheres are unlikely to be companion-induced artifacts. Five of the eight confirmed candidates have been reported as photometrically variable, suggesting that composite atmospheric indices are useful in identifying brown dwarfs with strongly heterogeneous cloud covers. We compare hot Jupiters and brown dwarfs in a near-infrared color-magnitude diagram. We confirm that the coldest hot Jupiters in our sample have spectra similar to mid-L dwarfs, and the hottest hot Jupiters have spectra similar to those of M-dwarfs. Our sample provides a uniform data set of a broad range of ultracool atmospheres, allowing large-scale comparative studies and providing an HST legacy spectral library.
2954. Cloud decomposition & SFR measurements
ID:
ivo://CDS.VizieR/J/ApJ/841/109
Title:
Cloud decomposition & SFR measurements
Short Name:
J/ApJ/841/109
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galactic star formation scaling relations show increased scatter from kpc to sub-kpc scales. Investigating this scatter may hold important clues to how the star formation process evolves in time and space. Here, we combine different molecular gas tracers, different star formation indicators probing distinct populations of massive stars, and knowledge of the evolutionary state of each star-forming region to derive the star formation properties of ~150 star-forming complexes over the face of the Large Magellanic Cloud (LMC). We find that the rate of massive star formation ramps up when stellar clusters emerge and boost the formation of subsequent generations of massive stars. In addition, we reveal that the star formation efficiency of individual giant molecular clouds (GMCs) declines with increasing cloud gas mass (M_cloud_). This trend persists in Galactic star-forming regions and implies higher molecular gas depletion times for larger GMCs. We compare the star formation efficiency per freefall time ({epsilon}_ff_) with predictions from various widely used analytical star formation models. While these models can produce large dispersions in {epsilon}_ff_ similar to those in observations, the origin of the model-predicted scatter is inconsistent with observations. Moreover, all models fail to reproduce the observed decline of {epsilon}_ff_ with increasing M_cloud_ in the LMC and the Milky Way. We conclude that analytical star formation models idealizing global turbulence levels and cloud densities and assuming a stationary star formation rate (SFR) are inconsistent with observations from modern data sets tracing massive star formation on individual cloud scales. Instead, we reiterate the importance of local stellar feedback in shaping the properties of GMCs and setting their massive SFR.
2955. Cloud-scale molecular gas properties in 15 galaxies
ID:
ivo://CDS.VizieR/J/ApJ/860/172
Title:
Cloud-scale molecular gas properties in 15 galaxies
Short Name:
J/ApJ/860/172
Date:
21 Oct 2021
Publisher:
CDS
Description:
We measure the velocity dispersion, {sigma}, and surface density, {Sigma}, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution 45-120pc, matched to the size of individual giant molecular clouds. Combining 11 galaxies from the PHANGS-ALMA survey with four targets from the literature, we characterize ~30000 independent sightlines where CO is detected at good significance. {Sigma} and {sigma} show a strong positive correlation, with the best-fit power-law slope close to the expected value for resolved, self-gravitating clouds. This indicates only a weak variation in the virial parameter {alpha}_vir_{propto}{sigma}^2^/{Sigma}, which is ~1.5-3.0 for most galaxies. We do, however, observe enormous variation in the internal turbulent pressure P_turb_{propto}{Sigma}{sigma}^2^, which spans ~5dex across our sample. We find {Sigma}, {sigma}, and P_turb_ to be systematically larger in more massive galaxies. The same quantities appear enhanced in the central kiloparsec of strongly barred galaxies relative to their disks. Based on sensitive maps of M31 and M33, the slope of the {sigma}-{Sigma} relation flattens at {Sigma}<~10M_{sun}_/pc^2^, leading to high {sigma} for a given {Sigma} and high apparent {alpha}_vir_. This echoes results found in the Milky Way and likely originates from a combination of lower beam-filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low-density regime.
2956. Clouds in SEDIGISM science demonstration field
ID:
ivo://CDS.VizieR/J/A+A/601/A124
Title:
Clouds in SEDIGISM science demonstration field
Short Name:
J/A+A/601/A124
Date:
21 Oct 2021
Publisher:
CDS
Description:
The origin and life-cycle of molecular clouds are still poorly constrained, despite their importance for understanding the evolution of the interstellar medium. Many large-scale surveys of the Galactic plane have been conducted recently, allowing for rapid progress in this field. Nevertheless, a sub-arcminute resolution global view of the large-scale distribution of molecular gas, from the diffuse medium to dense clouds and clumps, and of their relationship to the spiral structure, is still missing. We have carried out a systematic, homogeneous, spectroscopic survey of the inner Galactic plane, in order to complement the many continuum Galactic surveys available with crucial distance and gas-kinematic information. Our aim is to combine this data set with recent infrared to sub-millimetre surveys at similar angular resolutions. The SEDIGISM survey covers 78deg^2^ of the inner Galaxy (-60{deg}<l<+18{deg}, |b|<0.5{deg}) in the J=2-1 rotational transition of ^13^CO. This isotopologue of CO is less abundant than ^12^CO by factors up to 100. Therefore, its emission has low to moderate optical depths, and higher critical density, making it an ideal tracer of the cold, dense interstellar medium. The data have been observed with the SHFI single-pixel instrument at APEX. The observational setup covers the ^13^CO(2-1) and C^18^O(2-1) lines, plus several transitions from other molecules. The observations have been completed. Data reduction is in progress and the final data products will be made available in the near future. Here we give a detailed description of the survey and the dedicated data reduction pipeline. To illustrate the scientific potential of this survey, preliminary results based on a science demonstration field covering -20{deg}<l<-18.5{deg} are presented. Analysis of the ^13^CO(2-1) data in this field reveals compact clumps, diffuse clouds, and filamentary structures at a range of heliocentric distances. By combining our data with data in the (1-0) transition of CO isotopologues from the ThrUMMS survey, we are able to compute a 3D realization of the excitation temperature and optical depth in the interstellar medium. Ultimately, this survey will provide a detailed, global view of the inner Galactic interstellar medium at an unprecedented angular resolution of ~30".
2957. CL 0024+1654 UBVI photometry
ID:
ivo://CDS.VizieR/J/AJ/126/2644
Title:
CL 0024+1654 UBVI photometry
Short Name:
J/AJ/126/2644
Date:
21 Oct 2021
Publisher:
CDS
Description:
Wide-field (20x20arcmin^2^) UBVI images of intermediate-redshift (z=0.39), Butcher-Oemler cluster CL0024+1654 are being distributed. These data probe the rest-frame mid-UV properties over a much larger area than previous studies of CL0024+1654. These images were obtained with the 0.9m telescope at the NOAO Kitt Peak National Observatory in 1991-1992. The resolution is 0.68 arcsec/pix, and the field-of-view is 20arcmin^2^. The standard KPNO Harris filter set was used. We are distributing the individual U, B, V and I frames, as well as the combined U+B+V+I image. Using these data, SExtractor was used to construct a multi-color catalog of approximately 6000 objects in this field. We present both isophotal and aperture photometry in the catalog to be complete. We cross-matched the objects in our catalog with three other CL0024 datasets, and list the matching results in the distributed catalog. Our catalog includes the cross-references to data from Czoske et al., 2001, Cat. <J/A+A/372/391>; from Smail et al., 1997, Cat. <J/ApJS/110/213>; and from Dressler et al., 1999, Cat. <J/ApJS/122/51>.
2958. Clump properties in the LMC 30 Dor region
ID:
ivo://CDS.VizieR/J/ApJ/703/736
Title:
Clump properties in the LMC 30 Dor region
Short Name:
J/ApJ/703/736
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a complete ^12^CO(J=1-0) map of the prominent molecular ridge in the Large Magellanic Cloud (LMC) obtained with the 22m ATNF Mopra Telescope. The region stretches southward by ~2{deg} (or 1.7kpc) from 30 Doradus, the most vigorous star-forming region in the Local Group. The location of this molecular ridge is unique insofar as it allows us to study the properties of molecular gas as a function of the ambient radiation field in a low-metallicity environment. The mass spectrum and the scaling relations between the properties of the CO clumps in the molecular ridge are similar, but not identical, to those that have been established for Galactic molecular clouds.
2959. Clumps in NGC 7538 at 450 and 850{mu}m
ID:
ivo://CDS.VizieR/J/ApJ/625/891
Title:
Clumps in NGC 7538 at 450 and 850{mu}m
Short Name:
J/ApJ/625/891
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present submillimeter continuum maps at 450 and 850{mu}m of a 12'x8' region of the NGC 7538 high-mass star-forming region, made using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. We used an automated clump-finding algorithm to identify 67 clumps in the 450{mu}m image and 77 in the 850{mu}m image.
2960. Clumps in NGC 6334 from 450/850um observations
ID:
ivo://CDS.VizieR/J/AJ/136/2083
Title:
Clumps in NGC 6334 from 450/850um observations
Short Name:
J/AJ/136/2083
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 6334 is a galactic star-forming region in Scorpius, heavily obscured by intervening dust. The region consists of several major sites of star formation known previously from far-infrared (IR) and radio-wavelength observations. We present images of NGC 6334 obtained at wavelengths of 850 and 450um with the Submillimeter Common-User Bolometric Array at the James Clerk Maxwell Telescope. These data highlight the distribution of dense cold dust, a particularly striking feature of which is a narrow ridge of emission passing between most of the star-forming centers. We use a clump-finding technique to quantify the distribution of dust emission throughout the region, and we obtain estimates of the sizes, masses, and temperatures of the clump ensemble under simple assumptions.

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