- ID:
- ivo://CDS.VizieR/J/ApJ/805/157
- Title:
- BGPS. XIII. Mass functions
- Short Name:
- J/ApJ/805/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the distance probability density function (DPDF) formalism of Ellsworth-Bowers et al. (2015, J/ApJ/799/29) to derive physical properties for the collection of 1710 Bolocam Galactic Plane Survey (BGPS) version 2 sources with well-constrained distance estimates. To account for Malmquist bias, we estimate that the present sample of BGPS sources is 90% complete above 400M_{sun}_ and 50% complete above 70M_{sun}_. The mass distributions for the entire sample and astrophysically motivated subsets are generally fitted well by a lognormal function, with approximately power-law distributions at high mass. Power-law behavior emerges more clearly when the sample population is narrowed in heliocentric distance (power-law index {alpha}=2.0+/-0.1 for sources nearer than 6.5kpc and {alpha}=1.9+/0.1 for objects between 2 and 10 kpc). The high-mass power-law indices are generally 1.85<={alpha}<=2.05 for various subsamples of sources, intermediate between that of giant molecular clouds and the stellar initial mass function. The fit to the entire sample yields a high-mass power-law {alpha}^\^^=1.94_-0.10_^+0.34^. Physical properties of BGPS sources are consistent with large molecular cloud clumps or small molecular clouds, but the fractal nature of the dense interstellar medium makes it difficult to map observational categories to the dominant physical processes driving the observed structure. The face-on map of the Galactic disk's mass surface density based on BGPS dense molecular cloud structures reveals the high-mass star-forming regions W43, W49, and W51 to be prominent mass concentrations in the first quadrant. Furthermore, we present a 0.25kpc resolution map of the dense gas mass fraction across the Galactic disk that peaks around 5%.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1836
- Title:
- BLAST survey in Vela-D
- Short Name:
- J/ApJ/707/1836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) carried out a 250, 350, and 500um survey of the Galactic plane encompassing the Vela Molecular Ridge, with the primary goal of identifying the coldest dense cores possibly associated with the earliest stages of star formation. Here, we present the results from observations of the Vela-D region, covering about 4deg^2^, in which we find 141 BLAST cores. We exploit existing data taken with the Spitzer MIPS, IRAC, and SEST-SIMBA instruments to constrain their (single-temperature) spectral energy distributions, assuming a dust emissivity index {beta}=2.0. This combination of data allows us to determine the temperature, luminosity, and mass of each BLAST core, and also enables us to separate starless from protostellar sources. We also analyze the effects that the uncertainties on the derived physical parameters of the individual sources have on the overall physical properties of starless and protostellar cores, and we find that there appear to be a smooth transition from the pre- to the protostellar phase. In particular, for protostellar cores we find a correlation between the MIPS24 flux, associated with the central protostar, and the temperature of the dust envelope. We also find that the core mass function of the Vela-D cores has a slope consistent with other similar (sub)millimeter surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/915
- Title:
- BLAST view of Aquila star-forming region
- Short Name:
- J/ApJ/723/915
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out the first general submillimeter analysis of the field toward GRSMC 45.46+0.05, a massive star-forming region in Aquila. The deconvolved 6{deg}^2^ (3{deg}x2{deg}) maps provided by BLAST in 2005 at 250, 350, and 500um were used to perform a preliminary characterization of the clump population previously investigated in the infrared, radio, and molecular maps. Interferometric CORNISH data at 4.8GHz have also been used to characterize the Ultracompact HII regions (UCHIIRs) within the main clumps. By means of the BLAST maps, we have produced an initial census of the submillimeter structures that will be observed by Herschel, several of which are known Infrared Dark Clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/416/555
- Title:
- Brown Dwarfs in ChaI Dark Cloud
- Short Name:
- J/A+A/416/555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multiband survey for brown dwarfs in the Chamaeleon I dark cloud with the Wide Field Imager (WFI) camera at the ESO/MPG 2.2-m telescope on La Silla (Chile) on 28-May to 03-Jun 1999. The survey has revealed a substantial population of brown dwarfs in this southern star-forming region. Candidates were selected from R, I and H{alpha} imaging observations. We also observed in two medium-band filters, M855 and M915, for spectral type determination. The former filter covers a wavelength range containing spectral features characteristic of M-dwarfs, while the latter lies in a relatively featureless wavelength region for these late-type objects. A correlation was found between spectral type and (M855-M915) colour index for mid- to late M-type objects and early L-type dwarfs. With this method, we identify most of our object candidates as being of spectral type M5 or later. Our results show that there is no strong drop in the number of objects for the latest spectral types, hence brown dwarfs may be as abundant as low-mass stars in this region. Also, both kind of objects have a similar spatial distribution. We derive an index {alpha}=0.6+/-0.1 of the mass function in this region of dispersed star formation, in good agreement with the values obtained in other star forming regions and young clusters. Some of the brown dwarfs have strong H{alpha} emission, suggesting mass accretion. For objects with published infrared photometry, we find that strong H{alpha} emission is related to a mid-infrared excess, indicative of the existence of a circumstellar disk.
- ID:
- ivo://CDS.VizieR/J/MNRAS/355/1272
- Title:
- BVIJHKs photometry around CG 12
- Short Name:
- J/MNRAS/355/1272
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A method for determining distances to dark clouds and Bok globules based on broad-band optical and near-infrared photometry is presented. In this method, intrinsic colour indices of stars projected towards the direction of a cloud are computed by dereddening the observed colour indices using various trial values of extinction A_V_ and a standard extinction law. The computed intrinsic colour indices for a star are then compared with the intrinsic colour indices of normal main-sequence stars and a spectral type is assigned to the star for which the computed colour indices best match the standard intrinsic colour indices. Distances (d) to the stars are determined using the A_V_ and absolute magnitudes (M_V_) corresponding to the spectral types thus obtained. A plot of A_V_ against d undergoes a sharp rise at a distance corresponding to the distance to the cloud. Using this method, we have determined a distance of 550pc to the cometary globule CG 12.
- ID:
- ivo://CDS.VizieR/J/A+A/364/712
- Title:
- BV photometry in Draco molecular cloud
- Short Name:
- J/A+A/364/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To investigate the distance and linear dimensions of the Draco Molecular Cloud (MBM 41) we have obtained new CCD photometry for a selection of stars in 20 selected areas toward the cores of the cloud. The selected areas were chosen to coincide with the brightest IRAS emitting portions of the cloud, and also with dense ^12^CO emission from the cloud. For each area we have obtained V and B photometry, and a subset of the fields has also been observed through a narrow-band H{alpha} filter and in the U band. We present V and B magnitudes for the 362 stars which have high-quality observations in both bands. The observations were made during the nights of June 29 and June 30, 1993 at the Palomar Observatory, using the 1.5-meter telescope and Palomar 6 Tektronix CCD camera with 24 micron pixels.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A76
- Title:
- California molecular cloud CO datacubes
- Short Name:
- J/A+A/642/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dense molecular filaments are central to the star formation process, but the detailed manner in which they fragment into prestellar cores is not well understood yet. Here, we investigate the fragmentation properties and dynamical state of several star-forming filaments in the X-shaped nebula region of the California molecular cloud in an effort to shed some light on this issue. We used multiwavelength far-infrared images from Herschel as well as the getsources and getfilaments extraction methods to identify dense cores and filaments in the region and derive their basic properties. We also used a map of ^13^CO(2-1) emission from the Arizona 10m Submillimeter Telescope (SMT) to constrain the dynamical state of the filaments. We identified ten filaments with aspect ratios of AR>4 and column density contrasts of C>0.5, as well as 57 dense cores, including two protostellar cores, 20 robust prestellar cores, 11 candidate prestellar cores, and 24 unbound starless cores. All ten filaments have roughly the same deconvolved full width at half maximum (FWHM), with a median value of 0.12+/-0.03pc, which is independent of their column densities ranging from <10^21^cm^-2^ to >10^22^cm^-2^. Two star-forming filaments (# 8 and # 10) stand out since they harbor quasi-periodic chains of dense cores with a typical projected core spacing of ~0.15pc. These two filaments have thermally supercritical line masses and are not static. Filament 8 exhibits a prominent transverse velocity gradient, suggesting that it is accreting gas from the parent cloud gas reservoir at an estimated rate of ~40+/-10M_{sun}_/Myr/pc. Filament 10 includes two embedded protostars with outflows and it is likely at a somewhat later evolutionary stage than filament 8. In both cases, the observed (projected) core spacing is similar to the filament width and significantly shorter than the canonical separation of ~4 times the filament width predicted by classical cylinder fragmentation theory. It is unlikely that projection effects can explain this discrepancy. We suggest that the continuous accretion of gas onto the two star-forming filaments, as well as the geometrical bending of the filaments, may account for the observed core spacing. Our findings suggest that the characteristic fragmentation lengthscale of molecular filaments is quite sensitive to external perturbations from the parent cloud, such as the gravitational accretion of ambient material.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/49
- Title:
- Candidate YSOs in AFGL 333 with NEWFIRM & Spitzer
- Short Name:
- J/ApJ/822/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the key questions in the field of star formation is the role of stellar feedback on the subsequent star formation process. The W3 giant molecular cloud complex at the western border of the W4 super bubble is thought to be influenced by the massive stars in W4. This paper presents a study of the star formation activity within AFGL 333, a ~10^4^M_{sun}_ cloud within W3, using deep JHKs photometry obtained from the NOAO Extremely Wide Field Infrared Imager combined with Spitzer IRAC and MIPS photometry. Based on the infrared excess, we identify 812 candidate young stellar objects (YSOs) in the complex, of which 99 are Class I and 713 are Class II sources. The stellar density analysis of YSOs reveals three major stellar aggregates within AFGL333, namely AFGL 333 Main, AFGL 333 NW1 and AFGL 333 NW2. The disk fraction within AFGL 333 is estimated to be ~50%-60%. We use the extinction map made from the H-K_s_ colors of the background stars and CO data to understand the cloud structure and to estimate the cloud mass. From the stellar and cloud mass associated with AFGL 333, we infer that the region is currently forming stars with an efficiency of ~4.5% and at a rate of ~2-3M_{sun}_/Myr/pc^2^. In general, the star formation activity within AFGL 333 is comparable to that of nearby low mass star-forming regions. We do not find any strong evidence to suggest that the stellar feedback from the massive stars of nearby W4 super bubble has affected the global star formation properties of the AFGL 333 region.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2442
- Title:
- Catalog of bubbles from Milky Way Project
- Short Name:
- J/MNRAS/424/2442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of 5106 infrared bubbles created through visual classification via the online citizen science website The Milky Way Project. Bubbles in the new catalogue have been independently measured b at least five individuals, producing consensus parameters for their position, radius, thickness, eccentricity and position angle. Citizen scientists - volunteers recruited online and taking part in this research - have independently rediscovered the locations of at least 86 percent of three widely used catalogues of bubbles and HII regions whilst finding an order of magnitude more objects. 29 per cent of the Milky Way Project catalogue bubbles lie on the rim of a larger bubble, or have smaller bubbles located within them, opening up the possibility of better statistical studies of triggered star formation. Also outlined is the creation of a heat map of star formation activity in the Galactic plane. This online resource provides a crowd-sourced map of bubbles and arcs in the Milky Way, and will enable better statistical analysis of Galactic star formation sites.
