- ID:
- ivo://CDS.VizieR/J/ApJ/805/9
- Title:
- Gould's Belt VLA Survey. II. Serpens region
- Short Name:
- J/ApJ/805/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep (~17{mu}Jy) radio continuum observations of the Serpens molecular cloud, the Serpens south cluster, and the W40 region obtained using the Very Large Array in its A configuration. We detect a total of 146 sources, 29 of which are young stellar objects (YSOs), 2 of which are BV stars, and 5 more of which are associated with phenomena related to YSOs. Based on their radio variability and spectral index, we propose that about 16 of the remaining 110 unclassified sources are also YSOs. For approximately 65% of the known YSOs detected here as radio sources, the emission is most likely non-thermal and related to stellar coronal activity. As also recently observed in Ophiuchus, our sample of YSOs with X-ray counterparts lies below the fiducial Guedel & Benz (1993ApJ...405L..63G) relation. Finally, we analyze the proper motions of nine sources in the W40 region. This allows us to better constrain the membership of the radio sources in the region.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/775/63
- Title:
- Gould's Belt VLA Survey. I. Ophiuchus complex
- Short Name:
- J/ApJ/775/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present large-scale (~2000arcmin^2^), deep (~20{mu}Jy), high-resolution (~1") radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array at {lambda}=4 and 6cm. In total, 189 sources were detected, 56 of them associated with known young stellar sources, and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although we also detect four objects of A/F/B types and two brown dwarf candidates. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronas characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Gudel-Benz relation, but with a different normalization than the most radioactive types of stars. Finally, we detect a ~70mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/116
- Title:
- Gould's Belt VLA survey. V. Perseus region
- Short Name:
- J/ApJ/818/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiepoch, large-scale (~2000 arcmin^2^), fairly deep (~16 {mu}Jy), high-resolution (~1") radio observations of the Perseus star-forming complex obtained with the Karl G. Jansky Very Large Array at frequencies of 4.5 and 7.5 GHz. These observations were mainly focused on the clouds NGC 1333 and IC 348, although we also observed several fields in other parts of the Perseus complex. We detect a total of 206 sources, 42 of which are associated with young stellar objects (YSOs). The radio properties of about 60% of the YSOs are compatible with a nonthermal radio emission origin. Based on our sample, we find a fairly clear relation between the prevalence of nonthermal radio emission and evolutionary status of the YSOs. By comparing our results with previously reported X-ray observations, we show that YSOs in Perseus follow a Gudel-Benz relation with {kappa}=0.03, consistent with other regions of star formation. We argue that most of the sources detected in our observations but not associated with known YSOs are extragalactic, but provide a list of 20 unidentified radio sources whose radio properties are consistent with being YSO candidates. Finally, we also detect five sources with extended emission features that can clearly be associated with radio galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A25
- Title:
- GPS radio sources multifrequency study
- Short Name:
- J/A+A/544/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gigahertz peaked spectrum (GPS) radio sources are a class of extragalactic radio sources characterized by a spectral peak in the gigahertz domain. They are a mixed class of quasars and galaxies. A large proportion of the sources studied in the literature have only few data points in the radio domain, and the determination of variability and shape of the simultaneous spectra is inadequate. Sources currently included in the GPS source lists are very heterogeneous. We present the observational results from 12 observing campaigns (carried out between 2006 and 2010) at the RATAN-600 radio telescope to obtain the simultaneous radio spectra, which is valuable and necessary to derive genuine GPS sources from flat-spectrum radio sources caught in a flaring state when their spectra are temporarily inverted. The sample contains both quasar- and galaxy-type GPS (122 sources) identified in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/671
- Title:
- Gravitational waves from pulsars
- Short Name:
- J/ApJ/713/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a search for gravitational waves from 116 known millisecond and young pulsars using data from the fifth science run of the LIGO detectors. For this search, ephemerides overlapping the run period were obtained for all pulsars using radio and X-ray observations. We demonstrate an updated search method that allows for small uncertainties in the pulsar phase parameters to be included in the search. We report no signal detection from any of the targets and therefore interpret our results as upper limits on the gravitational wave signal strength. The most interesting limits are those for young pulsars. We present updated limits on gravitational radiation from the Crab pulsar, where the measured limit is now a factor of 7 below the spin-down limit. This limits the power radiated via gravitational waves to be less than ~2% of the available spin-down power. For the X-ray pulsar J0537-6910 we reach the spin-down limit under the assumption that any gravitational wave signal from it stays phase locked to the X-ray pulses over timing glitches, and for pulsars J1913+1011 and J1952+3252 we are only a factor of a few above the spin-down limit. Of the recycled millisecond pulsars, several of the measured upper limits are only about an order of magnitude above their spin-down limits. For these our best (lowest) upper limit on gravitational wave amplitude is 2.3x10^-26^ for J1603-7202 and our best (lowest) limit on the inferred pulsar ellipticity is 7.0x10^-8^ for J2124-3358.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/88
- Title:
- GRB 160509A VLA monitoring campain results
- Short Name:
- J/ApJ/833/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second multi-frequency radio detection of a reverse shock in a {gamma}-ray burst. By combining our extensive radio observations of the Fermi-Large Area Telescope {gamma}-ray burst 160509A at z=1.17 up to 20 days after the burst with Swift X-ray observations and ground-based optical and near-infrared data, we show that the afterglow emission comprises distinct reverse shock and forward shock contributions: the reverse shock emission dominates in the radio band at <~10 days, while the forward shock emission dominates in the X-ray, optical, and near-infrared bands. Through multi-wavelength modeling, we determine a circumburst density of n_0_~10^-3^cm^-3^, supporting our previous suggestion that a low-density circumburst environment is conducive to the production of long-lasting reverse shock radiation in the radio band. We infer the presence of a large excess X-ray absorption column, N_H_~1.5x10^22^cm^-2^, and a high rest-frame optical extinction, A_V_~3.4mag. We identify a jet break in the X-ray light curve at t_jet_~6days, and thus derive a jet opening angle of {theta}_jet_~4{deg}, yielding a beaming-corrected kinetic energy and radiated {gamma}-ray energy of E_K_~4x10^50^erg and E_{gamma}_~1.3x10^51^erg (1-10^4^keV, rest frame), respectively. Consistency arguments connecting the forward shocks and reverse shocks suggest a deceleration time of t_dec_~460s~T_90_, a Lorentz factor of {Gamma}(t_dec_)~330, and a reverse-shock-to-forward-shock fractional magnetic energy density ratio of R_B_={epsilon}_B,RS_/{epsilon}_B,FS_~8. Our study highlights the power of rapid-response radio observations in the study of the properties and dynamics of {gamma}-ray burst ejecta.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A141
- Title:
- G345.5+1.5 region multiwavelength study
- Short Name:
- J/A+A/623/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The star formation process requires the dust and gas present in the Milky Way to self-assemble into dense reservoirs of neutral material where the new generation of stars will emerge. Star-forming regions are usually studied in the context of Galactic surveys, but dedicated observations are sometimes needed when the study reaches beyond the survey area. A better understanding of the star formation process in the Galaxy can be obtained by studying several regions. This allows increasing the sample of objects (clumps, cores, and stars) for further statistical works and deeper follow-up studies. Here, we studied the G345.5+1.5 region, which is located slightly above the Galactic plane, to understand its star formation properties. We combined Large Apex BOlometer CAmera (LABOCA) and ^12^CO(4-3) transition line (NANTEN2) observations complemented with the Hi-GAL and Spitzer-GLIMPSE surveys to study the star formation toward this region. We used the Clumpfind algorithm to extract the clumps from the 870um and ^12^CO(4-3) data. Radio emission at 36cm was used to estimate the number of HII regions and to remove the contamination from the free-free emission at 870um. We employed color-color diagrams and spectral energy distribution (SED) slopes to distinguish between prestellar and protostellar clumps.We studied the boundedness of the clumps through the virial parameter. Finally, we estimated the star formation efficiency (SFE) and star formation rate (SFR) of the region and used the Schmidt-Kennicutt diagram to compare its ability to form stars with other regions of the Galactic plane. Of the 13 radio sources that we found using the MGPS-2 catalog, 7 are found to be associated with Hii regions corresponding to late-B or early-O stars. We found 45 870um clumps with diameters between 0.4 and 1.2pc and masses between 43M_{sun}_ and 3923M_{sun}_, and 107 ^12^CO clumps with diameters between 0.4 pc and 1.3pc and masses between 28M_{sun}_ and 9433M_{sun}_. More than 50% of the clumps are protostellar and bounded and are able to host (massive) star formation. High SFR and SFR density (S FR) values are associated with the region, with an SFE of a few percent. With submillimeter, CO transition, and short-wavelength infrared observations, our study reveals a population of massive stars, protostellar and bound starless clumps, toward G345.5+1.5. This region is therefore actively forming stars, and its location in the starburst quadrant of the Schmidt-Kennicutt diagram is comparable to other star-forming regions found within the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/ApJ/647/418
- Title:
- Ground-state OH masers in W3(OH) study
- Short Name:
- J/ApJ/647/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLBA observations of the ground-state hydroxyl masers in W3(OH) at 0.02km/s spectral resolution. Over 250 masers are detected, including 56 Zeeman pairs. Line shapes are predominantly Gaussian or combinations of several Gaussians, with normalized deviations typically of the same magnitude as in masers in other species.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1587
- Title:
- GRS/BGPS sources in Galactic Plane
- Short Name:
- J/MNRAS/431/1587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The line of sight through the Galactic plane between longitudes l=37.83{deg} and 42.50{deg} allows for the separation of Galactic Ring Survey molecular clouds into those that fall within the spiral arms and those located in the interarm regions. By matching these clouds in both position and velocity with dense clumps detected in the mm continuum by the Bolocam Galactic Plane Survey, we are able to look for changes in the clump formation efficiency (CFE), the ratio of clump to cloud mass, with Galactic environment. We find no evidence of any difference in the CFE between the interarm and spiral-arm regions along this line of sight. This is further evidence that, outside the Galactic Centre region, the large-scale structures of the Galaxy play little part in changing the dense, potentially star-forming structures within molecular clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A131
- Title:
- G287.84-0.82 SOFIA and APEX datacubes
- Short Name:
- J/A+A/626/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have mapped the G287.84-0.82 cometary globule (with the Treasure Chest cluster embedded in it) in the South Pillars region of Carina (i) in [CII], 63um [OI] , and CO(11-10) using the heterodyne receiver array upGREAT on SOFIA and (ii) in J=2-1 transitions of CO, ^13^CO, C^18^O and J=3-2 transitions of H_2_CO using the APEX telescope in Chile. We use these data to probe the morphology, kinematics, and physical conditions of the molecular gas and the photon dominated regions (PDRs) in G287.84-0.82. The velocity-resolved observations of [CII] and [OI] suggest that the overall structure of the pillar (with red-shifted photo evaporating tails) is consistent with the effect of FUV radiation and winds from eta-Car and O stars in Trumpler 16. The gas in the head of the pillar is strongly influenced by the embedded cluster, whose brightest member is an O9.5 V star, CPD -59 2661. The emission of the [CII] and [OI] lines peak at a position close to the embedded star, while all the other tracers peak at another position lying to the north-east consistent with gas being compressed by the expanding PDR created by the embedded cluster. The molecular gas inside the globule is probed with the J=2-1 transitions of CO and isotopologues as well as H_2_CO, and analyzed using a non-LTE model (escape-probability approach), while we use PDR models to derive the physical conditions of the PDR. We identify at least two PDR gas components; the diffuse part (~10^4cm^-3^) is traced by [CII], while the dense (n~2-8x10^5^cm^-3^) part is traced by [CII], [OI], CO(11-10). Using the the F=2-1 transition of [^13^CII] detected at 50 positions in the region, we derive optical depths (0.9-5), excitation temperatures of [CII] (80-255K), and N(C+) of 0.3-1x10^19^cm^-2^. The total mass of the globule is ~1000M_{sun}_, about half of which is traced by [CII]. The dense PDR gas has a thermal pressure of 10^7-10^8K/cm^3^, which is similar to the values observed in other regions.
