- ID:
- ivo://CDS.VizieR/J/ApJ/822/59
- Title:
- BGPS. XIV. Molecular cloud clumps GBT obs.
- Short Name:
- J/ApJ/822/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We sort 4683 molecular clouds between 10{deg}<l<65{deg} from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70{mu}m sources, mid-IR color-selected YSOs, H_2_O and CH_3_OH masers, and UCHII regions. We also present a combined NH_3_-derived gas kinetic temperature and H_2_O maser catalog for 1788 clumps from our own GBT 100m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial ({alpha}~0.7) with >75% of clumps with known distance being gravitationally bound ({alpha}<2). These samples show a statistically significant increase in the median clump mass of {Delta}M~170-370M_{sun}_ from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at dM/dt~200-440M_{sun}_/Myr for an average freefall 0.8Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii) a variation in the ratio of starless to protostellar clump lifetime that scales as ~M^-0.4^. By comparing to the observed number of CH_3_OH maser containing clumps, we estimate the phase lifetime of massive (M>10^3^M_{sun}_) starless clumps to be 0.37+/-0.08Myr (M/10^3^M_{sun}_)^-1^; the majority (M<450M_{sun}_) have phase lifetimes longer than their average freefall time.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/836/60
- Title:
- Bgri light curves of PTF11kmb and PTF12bho
- Short Name:
- J/ApJ/836/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [CaII] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to a limit of M_R_>-8.0mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. We show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. We also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/219
- Title:
- Bgr survey of Cl1613+3104 and Cl1600+4109
- Short Name:
- J/A+AS/115/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
1844. BH 176 and AM-2
- ID:
- ivo://CDS.VizieR/J/A+A/300/726
- Title:
- BH 176 and AM-2
- Short Name:
- J/A+A/300/726
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained VI photometry for two low Galactic latitude star clusters: BH 176 and AM-2, using the 2.2m and the 3.5m NTT telescopes at ESO. Their VI colour-magnitude diagrams reveal that: BH 176 may be a globular cluster, or a border line object between a globular cluster and a disk cluster, showing a red horizontal branch and an extended red giant branch. We estimate E(B-V)=0.77 and d_{sun}_=13.4kpc. AM-2 appears to be an intermediate age open cluster, for which a reddening E(B-V)=0.44 and d_{sun}_=12.4kpc are estimated. It is located in the outer regions of the Galactic disk.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/2116
- Title:
- BHB and RR Lyrae towards Anticentre and NGP
- Short Name:
- J/MNRAS/422/2116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 51 blue horizontal branch (BHB) stars, 12 possible BHB stars and 58 RR Lyrae stars in Anticentre fields. Their selection does not depend on their kinematics. Light curves and ephemerides are given for seven previously unknown RR Lyrae stars. All but four of the RR Lyrae stars are of Oosterhoff type I.
- ID:
- ivo://CDS.VizieR/J/ApJ/731/119
- Title:
- BHB candidates in Sagittarius stream
- Short Name:
- J/ApJ/731/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a sample of blue horizontal branch (BHB) stars from the Sloan Digital Sky Survey Data Release 7 (Cat. II/294) to explore the structure of the tidal tails from the Sagittarius Dwarf Galaxy. We use a method yielding BHB star candidates with up to ~70% purity from photometry alone. The resulting sample has a distance precision of roughly 5% and can probe distances in excess of 100kpc. Using this sample, we identify a possible extension to the trailing arm at distances of 60-80kpc from the Sun with an estimated significance of at least 3.8{sigma}. Current models predict that a distant "returning" segment of the debris stream should exist, but place it substantially closer to the Sun where no debris is observed in our data. Exploiting the distance precision of our tracers, we estimate the mean line-of-sight thickness of the leading arm to be ~3kpc, and show that the two "bifurcated" branches of the debris stream differ by only 1-2kpc in distance. With a spectroscopic very pure BHB star subsample, we estimate the velocity dispersion in the leading arm, 37km/s, which is in reasonable agreement with models of Sgr disruption. We finally present a sample of high-probability Sgr BHB stars in the leading arm of Sgr, selected to have distances and velocities consistent with Sgr membership, to allow further study.
- ID:
- ivo://CDS.VizieR/J/ApJ/684/1143
- Title:
- BHB candidates in the Milky Way
- Short Name:
- J/ApJ/684/1143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's circular velocity curve to ~60kpc, which is found to be slightly falling from the adopted value of 220km/s at the Sun's location, and implies M(<60kpc)=(4.0+/-0.7)x10^11^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A56
- Title:
- [BHB2007] 11 full stokes continuum ALMA images
- Short Name:
- J/A+A/616/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Polarized continuum emission at millimeter/sub-millimeter wavelengths is usually attributed to thermal emission from dust grains aligned through radiative torques with the magnetic field. However, recent theoretical work has shown that under specific conditions polarization may arise from self-scattering of thermal emission and by radiation fields from a nearby stellar object. We use multi-frequency polarization observations of a circumbinary disk to investigate how the polarization properties change at distinct frequency bands. Our goal is to discern the main mechanism responsible for the polarization through comparison between our observations and model predictions for each of the proposed mechanisms. We used the Atacama Large Millimeter/submillimeter Array to perform full polarization observations at 97.5GHz (Band 3), 233GHz (Band 6) and 343.5GHz (Band 7). The ALMA data have a mean spatial resolution of 28AU. The target is the Class I object BHB07-11, which is the youngest object in the Barnard 59 protocluster. Complementary Karl G. Jansky Very Large Array observations at 34.5GHz were also performed and revealed a binary system at centimetric continuum emission within the disk. We detect an extended and structured polarization pattern remarkably consistent among all three bands. The distribution of polarized intensity resembles a horseshoe shape with polarization angles following this morphology. From the spectral index between bands 3 and 7, we derive a dust opacity index beta ~1 consistent with maximum grain sizes larger than expected to produce self-scattering polarization in each band. The polarization morphology and the polarization levels do not match predictions from self-scattering. On the other hand, marginal correspondence is seen between our maps and predictions from radiation field assuming the brightest binary component as main radiation source. Previous molecular line data from BHB07-11 indicates disk rotation. We used the DustPol module of the ARTIST radiative transfer tool to produce synthetic polarization maps from a rotating magnetized disk model assuming combined poloidal and toroidal magnetic field components. The magnetic field vectors (i. e., the polarization vectors rotated by 90 degrees) are better represented by a model with poloidal magnetic field strength about 3 times the toroidal one. The similarity of our polarization patterns among the three bands provides a strong evidence against self-scattering and radiation fields. On the other hand, our data are reasonably well reproduced by a model of disk with toroidal magnetic field components slightly smaller than poloidal ones. The residual is likely due to the internal twisting of the magnetic field due to the binary system dynamics, which is not considered in our model.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1097
- Title:
- BHB stars in Century Survey Galactic Halo Project
- Short Name:
- J/AJ/130/1097
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss a 175{deg}2 spectroscopic survey for blue horizontal branch (BHB) stars in the Galactic halo. We use the Two Micron All Sky Survey (2MASS, <II/246>) and the Sloan Digital Sky Survey (SDSS) to select BHB candidates, and we find that the 2MASS and SDSS color selection is 38% and 50% efficient, respectively, for BHB stars. Our samples include one likely runaway B7 star 6kpc below the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/374/164
- Title:
- BH Cas VRI differential magnitudes
- Short Name:
- J/A+A/374/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD observations of the contact binary system BH Cas are presented in this paper. New times of minima and an ephemeris based on our observations are also given. Complete light curves obtained in the V, R and I filters have been analyzed with the Wilson-Devinney code to derive the geometrical and physical parameters of the system. The final solution leads to a contact configuration (f=~21-22%). We have found that the photometric mass ratio differs from the spectroscopic one by about 13%, a discrepancy which is not uncommon for other W UMa systems. The absolute elements of the system are used to study its evolutionary status. The results show that BH Cas is a fairly evolved W-type W UMa system.
