- ID:
- ivo://CDS.VizieR/J/A+A/543/A65
- Title:
- BLAST line survey toward Vela-D cloud
- Short Name:
- J/A+A/543/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Starless cores represent a very early stage of the star formation process, before collapse results in the formation of a central protostar or a multiple system of protostars. We use spectral line observations of a sample of cold dust cores, previously detected with the BLAST telescope in the Vela-D molecular cloud, to perform a more accurate physical and kinematical analysis of the sources. We present a 3-mm and 1.3-cm survey conducted with the Mopra 22-m and Parkes 64-m radio telescopes of a sample of 40 cold dust cores, including both starless and proto-stellar sources. 20 objects were also mapped using molecular tracers of dense gas. To trace the dense gas we used the molecular species NH3, N2H+, HNC, HCO+, H13CO+, HCN and H13CN, where some of them trace the more quiescent gas, while others are sensitive to more dynamical processes. The selected cores have a wide variety of morphological types and also show physical and chemical variations, which may be associated to different evolutionary phases. We find evidence of systematic motions in both starless and proto-stellar cores and we detect line wings in many of the proto-stellar cores. Our observations probe linear distances in the sources <~0.1pc, and are thus sensitive mainly to molecular gas in the envelope of the cores. In this region we do find that, for example, the radial profile of the N2H+(1-0) emission falls off more quickly than that of C-bearing molecules such as HNC(1-0), HCO+(1-0) and HCN(1-0). We also analyze the correlation between several physical and chemical parameters and the dynamics of the cores. Depending on the assumptions made to estimate the virial mass, we find that many starless cores have masses below the self-gravitating threshold, whereas most of the proto-stellar cores have masses which are near or above the self-gravitating critical value. An analysis of the median properties of the starless and proto-stellar cores suggests that the transition from the pre- to the proto-stellar phase is relatively fast, leaving the core envelopes with almost unchanged physical parameters.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/191/222
- Title:
- BLAST observations of the SEP field
- Short Name:
- J/ApJS/191/222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a survey carried out by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) on a 9deg^2^ field near the South Ecliptic Pole at 250, 350, and 500um. The median 1{sigma} depths of the maps are 36.0, 26.4, and 18.4mJy, respectively. We apply a statistical method to estimate submillimeter galaxy number counts and find that they are in agreement with other measurements made with the same instrument and with the more recent results from Herschel/SPIRE. Thanks to the large field observed, the new measurements give additional constraints on the bright end of the counts. We identify 132, 89, and 61 sources with S/N>=4 at 250, 350, 500um, respectively and provide a multi-wavelength combined catalog of 232 sources with a significance >=4{sigma} in at least one BLAST band.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/428
- Title:
- BLAST sources in Galactic plane survey
- Short Name:
- J/ApJ/681/428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a new 250, 350, and 500um Galactic plane survey taken with the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) in 2005. This survey's primary goal is to identify and characterize high-mass protostellar objects (HMPOs). The region studied here covers 4{deg}^2^ near the open cluster NGC 6823 in the constellation Vulpecula (l=59{deg}). We find 60 compact sources (<60" diameter) detected simultaneously in all three bands. Their SEDs are constrained through BLAST, IRAS, Spitzer MIPS, and MSX photometry, with inferred dust temperatures spanning ~12-40K assuming a dust emissivity index {beta}=1.5. The luminosity-to-mass ratio, a distance-independ ent quantity, spans ~0.2-130L_{sun}_/M_{sun}_. Distances are estimated from coincident ^13^CO(1-0) velocities combined with a variety of other velocity and morphological data in the literature. In total, 49 sources are associated with a molecular cloud complex encompassing NGC 6823 (distance ~2.3kpc), 10 objects with the Perseus arm (~8.5kpc), and one object is probably in the outer Galaxy (~14kpc). Near NGC 6823, the inferred luminosities and masses of BLAST sources span ~40-10^4^L_{sun}_ and ~15-700M_{sun}_, respectively. The mass spectrum is compatible with molecular gas masses in other high-mass star-forming regions. Several luminous sources appear to be ultracompact H II regions powered by early B stars. However, many of the objects are cool, massive gravitationally bound clumps with no obvious internal radiation from a protostar, and hence excellent HMPO candidates.
- 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/707/1779
- Title:
- BLAST: the redshift survey
- Short Name:
- J/ApJ/707/1779
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently surveyed ~8.7deg^2^ centered on Great Observatories Origins Deep Survey-South at 250, 350, and 500um. In Dye et al. (2009, Cat. J/ApJ/703/285), we presented the catalog of sources detected at 5{sigma} in at least one band in this field and the probable counterparts to these sources in other wavebands. In this paper, we present the results of a redshift survey in which we succeeded in measuring redshifts for 82 of these counterparts. The spectra show that the BLAST counterparts are mostly star-forming galaxies but not extreme ones when compared to those found in the Sloan Digital Sky Survey. Roughly one quarter of the BLAST counterparts contain an active nucleus. We have also investigated the cases where there are two possible counterparts to the BLAST source, finding that in at least half of these there is evidence that the two galaxies are physically associated, either because they are interacting or because they are in the same large-scale structure. Finally, we have made the first direct measurements of the luminosity function in the three BLAST bands.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1824
- Title:
- BLAST Vela sources
- Short Name:
- J/ApJ/707/1824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results from an unbiased 50deg^2^ submillimeter Galactic survey at 250, 350, and 500um from the 2006 flight of the Balloon-borne Large Aperture Submillimeter Telescope. The map has resolution ranging from 36" to 60" in the three submillimeter bands spanning the thermal emission peak of cold starless cores. We determine the temperature, luminosity, and mass of more than 1000 compact sources in a range of evolutionary stages and an unbiased statistical characterization of the population. From comparison with C^18^O data, we find the dust opacity per gas mass, {kappa}r=0.16cm^2^/g at 250um, for cold clumps. We find that 2% of the mass of the molecular gas over this diverse region is in cores colder than 14K, and that the mass function for these cold cores is consistent with a power law with index {alpha}=-3.22+/-0.14 over the mass range 14M_{sun}_<M<80M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/23
- Title:
- Blazar (sub-)mm & {gamma}-ray luminosities
- Short Name:
- J/ApJ/754/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The coexistence of Planck and Fermi satellites in orbit has enabled the exploration of the connection between the (sub-)millimeter and {gamma}-ray emission in a large sample of blazars. We find that the {gamma}-ray emission and the (sub-)mm luminosities are correlated over five orders of magnitude, L_{gamma}_{prop.to}L_(sub-)mm_. However, this correlation is not significant at some frequency bands when simultaneous observations are considered. The most significant statistical correlations, on the other hand, arise when observations are quasi-simultaneous within two months. Moreover, we find that sources with an approximate spectral turnover in the middle of the mm-wave regime are more likely to be strong {gamma}-ray emitters. These results suggest a physical relation between the newly injected plasma components in the jet and the high levels of {gamma}-ray emission.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A18
- Title:
- Blue stars with disk photometry in NGC 6611
- Short Name:
- J/A+A/521/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 and its parental cloud, the Eagle Nebula (M 16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. In our previous studies of the Eagle Nebula, we identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0um. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A69
- Title:
- Bright C_2_H emission in Lupus disks
- Short Name:
- J/A+A/631/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent ALMA surveys in different star-forming regions have shown that CO emission in protoplanetary disks is much fainter than expected. Accordingly, CO-based gas masses and gas/dust ratios are orders of magnitude lower than previously thought. This may be explained either as fast gas dispersal, or as chemical evolution and locking up of volatiles in larger bodies leading to the low observed CO fluxes. The latter processes lead to enhanced C/O ratios in the gas, which may be reflected in enhanced abundances of carbon-bearing molecules like C_2_H. The goal of this work is to employ C_2_H observations to understand whether low CO fluxes are caused by volatile depletion, or by fast gas dissipation. We present ALMA Cycle 4 C_2_H (N=3-2, J=7/2-5/2, F=4-3 and F=3-2) observations of a subsample of nine sources in the Lupus star-forming region. The integrated C_2_H emission is determined and compared to previous CO isotopologue observations and physical-chemical model predictions. Seven out of nine disks are detected in C_2_H, whose line emission is almost as bright as ^{13}CO. All detections are significantly brighter than the typical sensitivity of the observations, hinting at a bimodal distribution of the C_2_H line intensities. This conclusion is strengthened when our observations are compared with additional C_2_H observations of other disks. When compared with physical-chemical models run with DALI, the observed C_2_H fluxes can be reproduced only if some level of volatile carbon and oxygen depletion is allowed and [C]/[O]>1 in the gas. Models with reduced gas/dust ratios near unity fail instead to reproduce the observed C_2_H line luminosity. A steeper than linear correlation between C_2_H and CN emission line is found for the Lupus disks. This is linked to the fact that C_2_H emission lines are affected more strongly by [C]/[O] variations than CN lines. Ring-like structures are detected both in C_2_H and in continuum emission but, as for CN, they do not seem to be connected. Sz 71 shows ring shaped emission in both C_2_H and CN with the location of the peak intensity coinciding, within our 30 au resolution. Our new ALMA C_2_H observations favour volatile carbon and oxygen depletion rather than fast gas dispersal to explain the faint CO observations for most of the disks. This result has implications for disk-evolution and planet-formation theories, as disk gas masses may be larger than expected if CO is considered to be the main carbon carrier in the gas phase.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/1415
- Title:
- Bright white dwarfs IRAC photometry
- Short Name:
- J/MNRAS/459/1415
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We cross-correlate several sources of archival photometry for 1265 bright (V~16mag) white dwarfs (WDs) with available high signal-to-noise spectroscopy. We find 381 WDs with archival Spitzer+IRAC data and investigate this subsample for infrared excesses due to circumstellar dust. This large data set reveals 15 dusty WDs, including three new debris discs and the hottest WD known to host dust (WD 0010+280). We study the frequency of debris discs at WDs as function of mass. The frequency peaks at 12.5 per cent for 0.7-0.75M_{sun}_ WDs (with 3M_{sun}_ main-sequence star progenitors) and falls off for stars more massive than this, which mirrors predicted planet occurrence rates for stars of different masses.
