- ID:
- ivo://CDS.VizieR/J/MNRAS/402/603
- Title:
- Properties of SCUBA cores in Perseus mol. cloud
- Short Name:
- J/MNRAS/402/603
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new analysis of the properties of star-forming cores in the Perseus molecular cloud, identified in SCUBA 850um data originally presented by Hatchell et al. (2005, Cat. J/A+A/440/151). Our goal is to determine which core properties can be robustly identified and which depend on the extraction technique. Four regions in the cloud are examined: NGC 1333, IC348/HH211, L1448 and L1455. We identify clumps of dust emission using two popular automated algorithms, clfind and gaussclumps, finding 85 and 122 clumps in total, respectively. Using the catalogues of Hatchell et al. (2005, Cat. J/A+A/440/151), we separate these clumps into starless, Class 0 and Class I cores.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/181/321
- Title:
- Properties of Spitzer c2d dark clouds
- Short Name:
- J/ApJS/181/321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The c2d Spitzer Legacy project obtained images and photometry with both IRAC and MIPS instruments for five large, nearby molecular clouds. Three of the clouds were also mapped in dust continuum emission at 1.1mm, and optical spectroscopy has been obtained for some clouds. This paper combines information drawn from studies of individual clouds into a combined and updated statistical analysis of star-formation rates and efficiencies, numbers and lifetimes for spectral energy distribution (SED) classes, and clustering properties. Current star-formation efficiencies range from 3% to 6%; if star formation continues at current rates for 10Myr, efficiencies could reach 15-30%. Star-formation rates and rates per unit area vary from cloud to cloud; taken together, the five clouds are producing about 260M_{sun}_ of stars per Myr.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A206
- Title:
- Propynethial (HCCCHS) submm spectroscopy
- Short Name:
- J/A+A/642/A206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. The rotational spectrum was re-investigated up to 630GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J=107 and K_a_=24. Watson's symmetric top Hamiltonian in the I^r^ representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/31
- Title:
- Protoplanetary disk data in Cha I and Lupus
- Short Name:
- J/ApJ/847/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we investigate the relation between disk mass and mass accretion rate to constrain the mechanism of angular momentum transport in protoplanetary disks. We find a correlation between dust disk mass and mass accretion rate in Chamaeleon I with a slope that is close to linear, similar to the one recently identified in Lupus. We investigate the effect of stellar mass and find that the intrinsic scatter around the best-fit M_dust_-M_*_ and dM_acc_/dt-M_*_ relations is uncorrelated. We simulate synthetic observations of an ensemble of evolving disks using a Monte Carlo approach and find that disks with a constant {alpha} viscosity can fit the observed relations between dust mass, mass accretion rate, and stellar mass but overpredict the strength of the correlation between disk mass and mass accretion rate when using standard initial conditions. We find two possible solutions. In the first one, the observed scatter in M_dust_ and dM_acc_/dt is not primordial, but arises from additional physical processes or uncertainties in estimating the disk gas mass. Most likely grain growth and radial drift affect the observable dust mass, while variability on large timescales affects the mass accretion rates. In the second scenario, the observed scatter is primordial, but disks have not evolved substantially at the age of Lupus and Chamaeleon I owing to a low viscosity or a large initial disk radius. More accurate estimates of the disk mass and gas disk sizes in a large sample of protoplanetary disks, through either direct observations of the gas or spatially resolved multiwavelength observations of the dust with ALMA, are needed to discriminate between both scenarios or to constrain alternative angular momentum transport mechanisms such as MHD disk winds.
- ID:
- ivo://CDS.VizieR/J/ApJ/692/973
- Title:
- Protostars in Perseus, Serpens and Ophiuchus
- Short Name:
- J/ApJ/692/973
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased census of deeply embedded protostars in Perseus, Serpens, and Ophiuchus, assembled by combining large-scale 1.1mm Bolocam continuum and Spitzer Legacy surveys. We identify protostellar candidates based on their mid-infrared (mid-IR) properties, correlate their positions with 1.1mm core positions from Enoch et al. in 2006 (Cat. J/ApJ/638/293) and 2007ApJ...666..982E, and Young et al. in 2006ApJ...644..326Y, and construct well-sampled spectral energy distributions using our extensive wavelength coverage ({lambda}=1.25-1100um). Source classification based on the bolometric temperature yields a total of 39 Class 0 and 89 Class I sources in the three-cloud sample. We compare to protostellar evolutionary models using the bolometric temperature-luminosity diagram, finding a population of low-luminosity Class I sources that are inconsistent with constant or monotonically decreasing mass accretion rates.
- ID:
- ivo://CDS.VizieR/J/ApJ/704/606
- Title:
- Protostars in the Vela Molecular Cloud
- Short Name:
- J/ApJ/704/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the infrared variability of young stellar objects by means of two Spitzer-IRAC images of the Vela Molecular Cloud D (VMR-D) obtained in observations separated in time by about six months. By using the same space-born IR instrumentation, this study eliminates all the unwanted effects due to differences in sensitivity, confusion, saturation, calibration, and filter bandpasses, issues that are usually unavoidable when comparing catalogs obtained from different instruments. The VMR-D map covers about 1.5deg^2^ of a site where star formation is actively ongoing. We are interested in accreting pre-main sequence variables whose luminosity variations are due to intermittent events of disk accretion (i.e., active T Tauri stars and EXor-type objects). The variable objects have been selected from a catalog of more than 170000 sources detected at an S/N>=5 (Cat. J/ApJ/719/9). We then searched the sample of variables for ones whose photometric properties such as IR excess, color-magnitude relationships, and spectral energy distribution, are as close as possible to those of known EXor's. Indeed, the latter are monitored in a more systematic way than T Tauri stars and the mechanisms that regulate the observed phenomenology are exactly the same. Hence, the modalities of the EXor behavior are adopted as driving criterion for selecting variables in general. We ultimately selected 19 bona fide candidates that constitute a well defined sample of new variable targets for further investigation (monitoring, spectroscopy). Out of these, 10 sources present a Spitzer MIPS 24um counterpart, and have been classified as three Class I, five flat spectrum, and two Class II objects, while the spectral energy distribution of the other nine sources is compatible with evolutionary phases older than Class I.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/41
- Title:
- PS1 proper-motion survey for brown dwarfs. I. Taurus
- Short Name:
- J/ApJ/858/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3{pi} Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370deg^2^) and deeper (down to ~3M_Jup_) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution (R~100) near-infrared spectra to quantify reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (<=100-3M_Jup_ in Taurus). We have discovered 25 low-gravity (VL-G) and the first 11 intermediate-gravity (INT-G) substellar (M6-L1) members of Taurus, constituting the largest single increase of Taurus brown dwarfs to date. We have also discovered 1 new Pleiades member and 13 new members of the Perseus OB2 association, including a candidate very wide separation (58kau) binary. We homogeneously reclassify the spectral types and extinctions of all previously known Taurus brown dwarfs. Altogether our discoveries have thus far increased the substellar census in Taurus by ~40% and added three more L-type members (<~5-10M_Jup_). Most notably, our discoveries reveal an older (>10Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. The mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A21
- Title:
- Radio cubes of G82.65-2.00
- Short Name:
- J/A+A/608/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100-500m as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~12pc at the assumed distance of 620pc. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament. We have carried out line observations of several molecules, including CO isotopologues, HCO^+^, HCN, and CS with the Osaka 1.85m telescope and the Nobeyama 45m telescope. The spectral line data are used to derive velocity and column density information.
- ID:
- ivo://CDS.VizieR/J/A+A/504/127
- Title:
- Radio maps of Infrared Dark Cloud 18223-3
- Short Name:
- J/A+A/504/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine an Infrared Dark Cloud (IRDC) at high spatial resolution as a means to study rotation, outflow, and infall at the onset of massive star formation. The IRDC 18223-3 was observed at 1.1mm and 1.3mm with the Submillimeter Array (SMA) and follow-up short spacing information was obtained with the IRAM 30m telescope. Additional data were taken at 3mm with the IRAM Plateau de Bure interferometer (PdBI).
- ID:
- ivo://CDS.VizieR/J/ApJS/166/567
- Title:
- Radio Molecular lines in infrared dark clouds
- Short Name:
- J/ApJS/166/567
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 41 infrared dark clouds from the 8um maps of the Midcourse Space Experiment (MSX), selected to be found within 1deg^2^ areas centered on known ultracompact HII regions. We have mapped these infrared dark clouds in N_2_H^+^ 1->0, CS 2->1, and C^18^O 1->0 emission using the Five College Radio Astronomy Observatory. The maps of the different species often show striking differences in morphologies, indicating differences in evolutionary state and/or the presence of undetected, deeply embedded protostars. We derive an average mass for these clouds using N_2_H^+^ column densities of >>2500M_{sun}_, a value comparable to that found in previous studies of high-mass star-forming cores using other mass tracers. The line widths of these clouds are typically 2.0-2.9km/s. Based on the fact that they are dark at 8um, compact, and massive, and have large velocity dispersions, we suggest that these clouds may be the precursor sites of intermediate- and high-mass star formation.
