Emission from protostars at centimeter radio wavelengths has been shown to trace the free-free emission arising from ionizing shocks as a result of jets and outflows driven by protostars. Therefore, measuring properties of protostars at radio frequencies can provide valuable insights into the nature of their outflows and jets. We present a C-band (4.1 and 6.4cm) survey of all known protostars (Class0 and ClassI) in Perseus as part of the VLA Nascent Disk and Multiplicity (VANDAM) Survey. We examine the known correlations between radio flux density and protostellar parameters, such as bolometric luminosity and outflow force, for our sample. We also investigate the relationship between radio flux density and far-infrared line luminosities from Herschel. We show that free-free emission most likely originates from J-type shocks; however, the large scatter indicates that those two types of emission probe different time and spatial scales. Using C-band fluxes, we removed an estimation of free-free contamination from the corresponding Ka- band (9mm) flux densities that primarily probe dust emission from embedded disks. We find that the compact (<1") dust emission is lower for Class I sources (median dust mass 96M_{Earth}_) relative to Class 0 (248M_{Earth}_), but several times higher than in Class II (5-15M_{Earth}_). If this compact dust emission is tracing primarily the embedded disk, as is likely for many sources, this result provides evidence of decreasing disk masses with protostellar evolution, with sufficient mass for forming giant planet cores primarily at early times.
Observations are reported of H_2_ IR emission in the S(1) v=1-0 line at 2.121{mu}m in the Orion Molecular Cloud, OMC1, using the GriF instrument on the Canada-France-Hawaii Telescope. GriF uses a combination of adaptive optics and Fabry-Perot interferometry, yielding a spatial resolution of 0.15" to 0.18" and velocity discrimination as high as 1km/s. 193 bright H_2_ emission regions can be identified in OMC1. The general characteristics of these features are described in terms of radial velocities, brightness and spatial displacement of maxima of velocity and brightness, the latter to yield the orientation of flows in the plane of the sky. Strong spatial correlation between velocity and bright H_2_ emission is found and serves to identify many features as shocks.
Very Low-Luminosity Objects (VeLLOs) from 1.25-850um
Short Name:
J/ApJS/225/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a search for Very Low-Luminosity Objects (VeLLOs) in the Gould Belt (GB) clouds using infrared and sub-millimeter (sub-mm) data from 1.25 to 850{mu}m and our N_2_H^+^(J=1-0) observations. We modified the criteria by Dunham et al. (2008, J/ApJS/179/249) to select the VeLLOs in the GB clouds, finding 95 VeLLO candidates, 79 of which are newly identified in this study. Out of 95 sources, 44 were detected in both sub-mm continuum and N_2_H^+^ emission and were classified as Group A (the VeLLOs), and 51 sources detected in either sub-mm emission or N_2_H^+^ emission were classified with Group B as candidate VeLLOs. We find that these VeLLOs and the candidates are forming in environments different from those of the likely VeLLOs. Seventy-eight sources are embedded within their molecular clouds, and thus are likely VeLLOs forming in a dense environment. The remaining 17 sources are located in low-level extinction regions (A_V_<1) connected to the clouds, and can be either background sources or candidate substellar objects forming in an isolated mode. The VeLLOs and the candidates are likely more luminous and their envelopes tend to be more massive in denser environments. The VeLLOs and the candidates are more populous in the clouds where more YSOs form, indicating that they form in a manner similar to that of normal YSOs. The bolometric luminosities and temperatures of the VeLLOs are compared to predictions of episodic accretion models, showing that the low luminosities for most VeLLOs can be well explained by their status in the quiescent phases of a cycle of episodic mass accretion.
Spectral and luminosity classes, absolute magnitudes. color excesses, interstellar extinctions and distances are determined for 98 stars down to 13mag in the Barnard 1 dark cloud belonging to the Per OB2 association. The classification of stars is based on their photoelectric photometry in the Vilnius seven-color photometric system. The extinction vs. distance diagram exhibits the presence of two dust layers at 150 and 230pc distances. The distance of the first cloud, which gives an extinction AV of 0.3mag, coincides with the distance of the Taurus dark cloud complex. The second cloud with much larger extinction is about at the same distance as the clouds in the direction of the nearby objects: reflection nebula NGC 1333 and open cluster IC 348.
157 stars down to 11th mag in a 3{deg}x4{deg} area at l=149{deg}, b=-0.3{deg} have been measured in the Vilnius photometric system. Magnitudes V, color indices, spectral classes, absolute magnitudes, color excesses and distances of the stars are determined. The interstellar extinction in all the area appears at a distance of about 100pc, grows monotonically and at a distance of 500pc it reaches ~2mag in the area of the dark cloud L1391 and 0.7-1.7mag in the remaining area. At larger distances the extinction is affected by a selection effect.
Seven-color photometry in the Vilnius system for 309 stars down to 12.5mag in the area along the galactic equator near the Camelopardalis and Perseus border is presented. Photometric spectral and luminosity classes of the stars are determined.
Magnitudes and color indices of 439 stars down to V~17.5mag in the eight-color Vilnius + I photometric system were obtained in four areas of diameters 20' within the dark cloud L935 separating the North America and Pelican nebulae. Spectral types, interstellar color excesses, extinctions and distances of stars were determined from the photometric data.
The results of photoelectric photometry in the Vilnius seven-color system are given for 152 stars down to 12.2mag in the area of the molecular cloud MBM 12 and the dust clouds L1454 and L1457 in Aries. The results of photometric classification of stars are also given. The investigation of interstellar extinction in the area is described in the next paper, Straizys et al., Cat. <J/BaltA/11/231>.
The results of photoelectric photometry in the Vilnius seven-color system and photometric classification are given for 419 stars down to ~11.0mag in a 5x10sq. degree area in the direction of the Serpens Cauda dark clouds.
The results of CCD photometry in the seven-color Vilnius system are given for 727 stars down to V~17 mag in a 1.5 square degree field in the region of dark cloud TGU H994 P1 (or LDN 1399, LDN 1400 and LDN 1402) in Camelopardalis. Using the intrinsic color indices and photometric reddening-free Q-parameters, two-dimensional spectral types for 73% of stars are determined.
