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121. Velocities of stars in the Orion Nebula Cluster
ID:
ivo://CDS.VizieR/J/ApJ/676/1109
Title:
Velocities of stars in the Orion Nebula Cluster
Short Name:
J/ApJ/676/1109
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from 1351 high-resolution spectra of 1215 stars in the Orion Nebula Cluster (ONC) and the surrounding Orion 1c association, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5m MMT. We confirmed 1111 stars as members, based on their radial velocity and/or H{alpha} emission. The radial velocity distribution of members shows a dispersion of {sigma}=3.1km/s. We found a substantial north-south velocity gradient and spatially coherent structure in the radial velocity distribution, similar to that seen in the molecular gas in the region. We also identified several binary and high velocity stars, a region exhibiting signs of triggered star formation, and a possible foreground population of stars somewhat older than the ONC.
122. VLA 33GHz obs. of star-forming regions
ID:
ivo://CDS.VizieR/J/ApJS/234/24
Title:
VLA 33GHz obs. of star-forming regions
Short Name:
J/ApJS/234/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 33GHz imaging for 112 pointings toward galaxy nuclei and extranuclear star-forming regions at ~2" resolution using the Karl G. Jansky Very Large Array (VLA) as part of the Star Formation in Radio Survey. A comparison with 33GHz Robert C. Byrd Green Bank Telescope single-dish observations indicates that the interferometric VLA observations recover 78%+/-4% of the total flux density over 25" regions (~kpc scales) among all fields. On these scales, the emission being resolved out is most likely diffuse non-thermal synchrotron emission. Consequently, on the ~30-300pc scales sampled by our VLA observations, the bulk of the 33GHz emission is recovered and primarily powered by free-free emission from discrete HII regions, making it an excellent tracer of massive star formation. Of the 225 discrete regions used for aperture photometry, 162 are extranuclear (i.e., having galactocentric radii rG>=250pc) and detected at >3{sigma} significance at 33GHz and in H{alpha}. Assuming a typical 33GHz thermal fraction of 90%, the ratio of optically-thin 33GHz to uncorrected H{alpha} star formation rates indicates a median extinction value on ~30-300pc scales of A_H{alpha}_~1.26+/-0.09mag, with an associated median absolute deviation of 0.87mag. We find that 10% of these sources are "highly embedded" (i.e., A_H{alpha}_>~3.3mag), suggesting that on average, HII regions remain embedded for <~1Myr. Finally, we find the median 33GHz continuum-to-H{alpha} line flux ratio to be statistically larger within rG<250pc relative to the outer disk regions by a factor of 1.82+/-0.39, while the ratio of 33GHz to 24{mu}m flux densities is lower by a factor of 0.45+/-0.08, which may suggest increased extinction in the central regions.
123. VPHAS+ DR2 survey
ID:
ivo://CDS.VizieR/II/341
Title:
VPHAS+ DR2 survey
Short Name:
II/341
Date:
21 Oct 2021
Publisher:
CDS
Description:
The primary goal of the VST Photometric H{alpha} Survey of the Southern Galactic Plane and Bulge (VPHAS+) is to collect single-epoch ugri broad-band and Ha narrow-band photometry across the southern Galactic Plane within the latitude range -5{deg}<b<+5{deg} down to point source magnitudes of ~21 or better. The VPHAS+ footprint also includes the inner Galactic Bulge, defined as a 20x20 deg^2^ box around the Galactic Centre: this assures optical coverage of the full VVV footprint. For all massive OBA stars this survey is deep enough to explore all but the most heavily obscured locations of the southern Plane, reaching to >4kpc from the Sun. These data will increase the number of known southern emission line stars by up to an order of magnitude, yielding much better statistics on important short-lived types of object. The wide-area uniform photometry obtained will also facilitate stellar population studies, capable of tracing structure over much of the southern Plane. VPHAS+ will trawl the star-formation history of the Galaxy as seen in stellar remnants of all types.
124. VRIH{alpha} photometry in NGC 2264
ID:
ivo://CDS.VizieR/J/AJ/135/441
Title:
VRIH{alpha} photometry in NGC 2264
Short Name:
J/AJ/135/441
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have performed deep wide-field CCD photometry of the young open cluster NGC 2264 to study the extent of star-forming regions (SFRs) and the shape of the initial mass function. In this paper, we present VRI and H{alpha} photometry for more than 67,000 stars. From the spatial distribution of the selected H{alpha} emission stars, we identify two active SFRs and a less active halo region surrounding these two SFRs. There are several H{alpha} emission stars in the field region outside the halo region, and these may be newly formed stars in the Mon OB1 association surrounding the cluster. The locus of pre-main-sequence (PMS) stars in the I_C_ versus V-I_C_ diagram is revised from the distribution of H{alpha} and X-ray emission stars in the diagram.
125. VRIHalpha photometry of M34
ID:
ivo://CDS.VizieR/J/MNRAS/370/954
Title:
VRIHalpha photometry of M34
Short Name:
J/MNRAS/370/954
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the results of a V- and i-band time-series photometric survey of M34 (NGC 1039) using the Wide Field Camera (WFC) on the Isaac Newton Telescope (INT), achieving better than 1 per cent precision per data point for 13~<i~<17. Candidate cluster members were selected from a V versus VI colour-magnitude diagram over 14<V<24 (0.12<M/M_{sun}_<1.0), finding 714 candidates, of which we expect ~400 to be real cluster members (taking into account contamination from the field). The mass function was computed, and found to be consistent with a lognormal distribution in dN/dlogM. Searching for periodic variable objects in the candidate members gave 105 detections over the mass range 0.25<M/M_{sun}_<1.0. The distribution of rotation periods for 0.4<M/M_{sun}_<1.0 was found to peak at ~7d, with a tail of fast rotators down to periods of ~0.8d. For 0.25<M/M_{sun}_<0.4 we found a peak at short periods, with a lack of slow rotators (e.g. P>5d), consistent with the work of other authors at very low masses. Our results are interpreted in the context of previous work, finding that we reproduce the same general features in the rotational period distributions. A number of rapid rotators were found with velocities ~ a factor of 2 lower than in the Pleiades, consistent with models of angular momentum evolution assuming solid body rotation without needing to invoke core-envelope decoupling.
126. WHAM Northern Sky Survey, V-1.1
ID:
ivo://CDS.VizieR/II/249
Title:
WHAM Northern Sky Survey, V-1.1
Short Name:
II/249
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Wisconsin H-Alpha Mapper has been designed to produce a survey of H-Alpha emission from the interstellar medium (ISM) over the entire northern sky. The instrument combines a 0.6 meter telescope and a dual-etalon 15cm Fabry-Perot spectrometer. In the primary spectral mode, an exposure captures a 200km/s spectral region with 8-12km/s velocity resolution from a one-degree beam on the sky. With a large-aperture design and modern CCD technology, WHAM can detect Galactic emission as faint as 0.05 Rayleighs in a 30 second exposure. For gas at 10000K, this observed intensity corresponds to an emission measure of about 0.1cm^-6^pc, more than 10 million times fainter than the Orion Nebula.

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