Search

Start Over Validation Level 2
23751. VLA 22GHz water masers obs. in NGC6334I-MM1
ID:
ivo://CDS.VizieR/J/ApJ/866/87
Title:
VLA 22GHz water masers obs. in NGC6334I-MM1
Short Name:
J/ApJ/866/87
Date:
21 Oct 2021
Publisher:
CDS
Description:
We compare multi-epoch sub-arcsecond Very Large Array imaging of the 22GHz water masers toward the massive protocluster NGC 6334I observed before and after the recent outburst of MM1B in (sub)millimeter continuum. Since the outburst, the water maser emission toward MM1 has substantially weakened. Simultaneously, the strong water masers associated with the synchrotron continuum point source CM2 have flared by a mean factor of 6.5 (to 4.2kJy) with highly blueshifted features (up to 70km/s from the LSR) becoming more prominent. The strongest flaring water masers reside 3000au north of MM1B and form a remarkable bow shock pattern whose vertex coincides with CM2 and tail points back to MM1B. Excited OH masers trace a secondary bow shock located ~120au downstream. Atacama Large Millimeter Array images of CS (6-5) reveal a highly collimated north-south structure encompassing the flaring masers to the north and the nonflaring masers to the south seen in projection toward the MM3-UCHII region. Proper motions of the southern water masers over 5.3 years indicate a bulk projected motion of 117km/s southward from MM1B with a dynamical time of 170 years. We conclude that CM2, the water masers, and many of the excited OH masers trace the interaction of the high-velocity bipolar outflow from MM1B with ambient molecular gas. The previously excavated outflow cavity has apparently allowed the radiative energy of the current outburst to propagate freely until terminating at the northern bow shock where it strengthened the masers. Additionally, water masers have been detected toward MM7 for the first time, and a highly collimated CS (6-5) outflow has been detected toward MM4.
23752. VLA GOODS-North Field 1.4-GHz Source Catalog
ID:
ivo://nasa.heasarc/vlagoodsn
Title:
VLA GOODS-North Field 1.4-GHz Source Catalog
Short Name:
VLAGOODSN
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey-North (GOODS-North) field. (The GOODS-North field covers ~160 arcmin<sup>2</sup> centered on the Hubble Deep Field North (Williams et al. 1996, AJ, 112, 1335) and is unrivaled in terms of its ancillary data sets, which include extremely deep Chandra, Hubble Space Telescope (HST), and Spitzer observations, deep UBVRIJHK ground-based imaging and ~3500 spectroscopic redshifts from 8 to 10 m telescopes). The resulting 1.4-GHz map has a synthesized beam size of ~1.7" and an rms noise level of ~3.9 microJansky per beam (µJy/beam) near its center and ~8 µJy/beam at 15 arcminutes from phase center. The authors have cataloged 1230 discrete radio emitters, within a 40' x 40' region, above a 5-sigma detection threshold of ~20 uJy at the field center. New techniques, pioneered by Owen & Morrison (2008, AJ, 136, 1889), have enabled the authors to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. The authors compare the 1.4-GHz (20-cm) source counts with those from other published radio surveys. Their differential counts are nearly Euclidean below 100 uJy with a median source diameter of ~1.2". This adds to the evidence presented by Owen & Morrison that the natural confusion limit may lie near 1 uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of their log N-log S, this indicates that the cutoff must be fairly sharp below 1 uJy, else the cosmic microwave background temperature would increase above 2.7K at 1.4GHz. A useful combined total of 165 hours of NRAOS's Very Large Array (VLA) A-configuration 1.4-GHz observations were obtained between 2005 February and 2006 February, all done at night so as to avoid solar interference, for a region centered at RA and Dec of 12:36:49.4, +62:12:58 (J2000). (See Table 1 of the reference paper for the VLA observing log) This table was created by the HEASARC in September 2013 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/188/178">CDS Catalog J/ApJS/188/178</a> file table2.dat This is a service provided by NASA HEASARC .
23753. VLA Goulds Belt Survey Ophiuchus Complex Source Catalog
ID:
ivo://nasa.heasarc/vlagbsoph
Title:
VLA Goulds Belt Survey Ophiuchus Complex Source Catalog
Short Name:
VLAGBSOPH
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from large-scale (~2000 arcmin<sup>2</sup>), deep (~20 µJy), high-resolution (~1") radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array (JVLA) at wavelengths of 4 and 6 cm (frequencies of 7.5 and 4.5 GHz). In total, 189 sources were detected, 56 of them associated with known young stellar objects (YSOs), 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 four objects of A/F/B types and two brown dwarf candidates are also detected. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronae 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 radio-active types of stars. Finally, the authors detected a ~70 mJy 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. The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO). Two frequency sub-bands, each 1-GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The observations were obtained on three different epochs (2011 February 17/19, April 3/4, and May 4/6) typically separated from one another by a month. The angular resolution of the observations is of the order of 1 arcsecond. To identify sources in their observations, the authors used the images corresponding to the concatenation of the three epochs, which provided the highest sensitivity. The criteria used to consider a detection as firm were: (1) sources with reported counterparts and a flux larger than four times the rms noise of the area, or (2) sources with a flux larger than five times the rms noise of the area and without reported counterparts. The authors searched the literature for previous radio detections, and for counterparts at X-ray, optical, near-infrared, and mid-infrared wavelengths. The search was done in SIMBAD, and accessed all the major catalogs (listed explicitly in the footnote of Table 3 in the reference paper). Note that the Spitzer c2d catalog includes cross-references to other major catalogs which were taken into account in their counterpart search. The authors considered a radio source associated with a counterpart at another wavelengths if the separation between the two was below the combined uncertainties of the two data sets. This was about 1.5 arcseconds for the optical and infrared catalogs, but could be significantly larger for some of the radio catalogs (for instance, the NVSS has a positional uncertainty of about 5 arcseconds). The authors found that only 76 of the sources detected here had previously been reported at radio wavelengths (matches are listed in the radio_name parameter in such cases), while the other 113 are new radio detections. On the other hand, they found a total of 100 counterparts at other wavelengths. Note that there are a significant number of sources that were previously known at radio wavelengths and have known counterparts at other frequencies. As a consequence, the number of sources that were previously known (at any frequency) is 134, while 55 of the sources in this sample are reported here for the first time. The authors argue that most of these 55 objects are likely background sources. They note, however, that 18 of the 129 unclassified objects (55 identified here for the first time and 74 previously known at radio wavelengths) are compact, have a positive spectral index, or exhibit high variability. Since these latter two properties are not expected of quasars (which are certainly variable, but usually not strongly on such short timescale), but would be natural characteristics of young stars, the authors argue that a small population of YSOs might be present among the unclassified sources. This population could account for, at most, 15% of the unclassified sources, and possibly significantly less. This table was created by the HEASARC in July 2015 based on electronic versions of Tables 1, 3 and 5 from the reference paper, which were obtained from the CDS (Catalog J/ApJ/775/63 files table1.dat, table3.dat and table5.dat). This is a service provided by NASA HEASARC .
23754. VLA Goulds Belt Survey Orion Complex Source Catalog
ID:
ivo://nasa.heasarc/vlagbsori
Title:
VLA Goulds Belt Survey Orion Complex Source Catalog
Short Name:
VLAGBSORI
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from a high-sensitivity (60 µJy), large-scale (2.26 deg<sup>2</sup>) survey obtained with the Karl G. Jansky Very Large Array (JVLA) as part of the Gould's Belt Survey (GBS) program. The authors detected 374 and 354 sources at 4.5 and 7.5 GHz, respectively. Of these, 148 are associated with previously known young stellar objects (YSOs). Another 86 sources previously unclassified at either optical or infrared wavelengths exhibit radio properties that are consistent with those of young stars. The overall properties of these sources at radio wavelengths such as their variability and radio to X-ray luminosity relation are consistent with previous results from the GBS. These detections provide target lists for follow-up Very Long Baseline Array radio observations to determine their distances, as YSOs are located in regions of high nebulosity and extinction, making it difficult to measure their optical parallaxes. The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO) in its A configuration. The observations of the 210 fields in the Orion Molecular Clouds A and B were obtained in three different epochs (2011 June 25 to July 4, July 23 to 30, and August 25 to 29, as described in Table 1 of the reference paper) typically separated from one another by a month. The 210 individual fields have been split into 7 maps, with 30 fields being observed per map, as follows: 12 in the lambda Ori region, 3 in L1622, 27 are shared between NGC 2068 and NGC 2071, 14 are shared between NGC 2023 and NGC 2024, 11 in the sigma Ori region, 109 in the Orion Nebula Cluster (ONC), 16 in L1641-N, 8 in L1641-C, and 10 in L1641-S (see Figures 1 to 7 in the reference paper). Two frequency sub-bands, each 1-GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The authors achieved a nearly uniform rms noise of 60 µJy beam<sup>-1</sup> at both frequencies in all the regions. The only exception to this is in the Trapezium region due to nebular emission; there the noise was 200 µJy beam<sup>-1</sup> after excluding baselines smaller than 150 kilo-lambda during imaging to remove extended emission. Sources were identified through a visual inspection of the individual fields at 4.5 GHz during the cleaning and imaging process since an automated source identification was deemed to be not sufficiently advanced and produced results that were too unreliable. In particularly clustered regions such as the Trapezium and NGC 2024, in addition to standard imaging, data from all three epochs were combined into a single image for source identification purposes only to improve statistical significance of each detection. The authors detected a combined total of 374 sources among the three epochs for all of the regions. All sources but one had fluxes greater than five times the rms noise in at least one epoch. The remaining source, 'GBS-VLA J053518.67-052033.1', was detected at two epochs with maximum detection probability of 4.9 sigma in a single epoch data. It is found in the Trapezium region, and has known counterparts in other wavelength regimes. The authors cross-referenced their catalog of sources with previous major radio, infrared, optical and X-ray surveys of the regions published in the literature. They have generally considered sources in these surveys to be counterparts if they had positional coincidences less than 1 arcsecond, but have allowed for larger offsets if the combined uncertainty between the databases was large. Of 374 detected sources, 261 have been previously found at another wavelength region, while 113 are new detections. 146 sources have been detected in X-rays, 94 at optical wavelengths, 218 at infrared, and 63 in previous radio surveys. Of the previously identified sources, 1 is extragalactic, while the other 148 as young stellar objects (YSOs). Of the YSOs, 106 have been placed on the standard class system based on the IRAC color-color classification of Allen et al. (2004, ApJS, 154, 363). There are 11 Class 0/I, 26 Class II, and 70 Class III type stars. A total of 225 sources are either new detections or, to the authors' knowledge, have not been previously classified in the literature. Of these remaining objects, they have identified 86 as exhibiting variability or high levels of circular polarization. While the authors cannot exclude the possibility that any of them are extragalactic in nature, quasars are not expected to vary as strongly on timescales of few weeks to few months, and exhibit very weak circular polarization, so these sources (listed in Table 5 of the reference paper) are likely YSO candidates. Using the same criteria of variability and circular polarization would identify only 107 of the 148 previously-known YSOs; thus we cannot tell which of the remaining 139 unidentified sources are YSOs or extragalactic objects. This table was created by the HEASARC in July 2015 based on electronic versions of Tables 2 and 4 from the reference paper, which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
23755. VLA Goulds Belt Survey Perseus Region Source Catalog
ID:
ivo://nasa.heasarc/vlagbsper
Title:
VLA Goulds Belt Survey Perseus Region Source Catalog
Short Name:
VLAGBSPER
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains a source catalog from multi-epoch, large-scale (~2,000 arcmin<sup>2</sup>), fairly deep (~16 microJansky or uJy), high-resolution (~1") radio observations of the Perseus star-forming complex that were obtained with the Karl G. Jansky Very Large Array (VLA) at frequencies of 4.5 and 7.5 GHz. These observations were mainly focused on the clouds NGC 1333 and IC 348, although the authors also observed several fields in other parts of the Perseus complex. They 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 non-thermal radio emission origin. Based on their sample, the authors find a fairly clear relation between the prevalence of non-thermal radio emission and the evolutionary status of the YSOs. By comparing their results with previously reported X-ray observations, they show that YSOs in Perseus follow a Gudel-Benz relation with a value of the kappa parameter (L<sub>X</sub>/L<sub>rad</sub> = kappa x 10<sup>(15.5 +/- 1)</sup> [Hz]) of 0.03, consistent with other regions of star formation. The authors argue that most of the sources detected in their observations that are not associated with known YSOs are extragalactic, but provide a list in the reference paper Of 20 unidentified radio sources whose radio properties are consistent with them being YSO candidates. Finally, they also detect five sources with extended emission features that can clearly be associated with radio galaxies. The observations were collected with the VLA of the National Radio Astronomy Observatory in B and BnA configurations. Two frequency sub-bands, each 1 GHz wide and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The observations were obtained in three observing sessions, on 2011 March 06/13, April 14/25, and May 01/02/10/19/22, typically separated from one another by a month. This dual-frequency, multi-epoch strategy was chosen to enable the characterization of the spectral index and variability of the detected sources, as well as to help with the identification of the emission mechanisms. The locations of the VLA observations are shown in Figure 1 of the reference paper. Other details of the observations are given in Table 1 of the reference paper. The approximate positions of the two main fields observed are: <pre> RA (ICRS) DE Designation(s) </pre> 03 28 55 +31 22.2 Ced 16 = NGC 1333 03 44 34 +32 09.8 NAME omi Per Cloud = IC 348 <pre> This HEASARC table contains the contents of Table 2 (74 radio sources detected in NGC 1333), Table 3 (91 radio sources detected in IC 348) and Table 4 (41 radio sources detected in single fields in Perseus) from the reference paper, totaling 206 radio sources. This table was created by the HEASARC in February 2018 based on an ASCII version of Table 2 from the reference paper that was obtained from the ApJ website and on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/818/116">CDS catalog J/ApJ/818/116</a> files table3.dat and table4.dat that contains Tables 3 and 4 from the reference paper. This is a service provided by NASA HEASARC .
23756. VLA Goulds Belt Survey Serpens Region Source Catalog
ID:
ivo://nasa.heasarc/vlagbsser
Title:
VLA Goulds Belt Survey Serpens Region Source Catalog
Short Name:
VLAGBSSER
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from a deep (~17 µJy) radio continuum observations of the Serpens molecular cloud, the Serpens south cluster, and the W40 region that were obtained using the Jansky Very Large Array (JVLA) in its A configuration. The authors detected 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, the authors 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, this sample of YSOs with X-ray counterparts lies below the fiducial Guedel & Benz (1993, ApJ, 405, L63) relation. In the reference paper, the authors analyze the proper motions of nine sources in the W40 region, thus allowing them to better constrain the membership of the radio sources in the region. The Serpens molecular cloud and the Serpens South cluster were observed in the same observing sessions on three different epochs (2011 June 17, July 19, and September 12 UT), using 25 and 4 pointings, respectively, with the JVLA at 4.5 and 4.5GHz. The W40 region, on the other hand, was only observed on two epochs (2011 June 17 and July 16), using 13 pointings. The details of the observations are listed in Table 1 of the reference paper. The authors adopted the same criteria as Dzib et al. (2013, ApJ, 775, 63) to consider a detection as firm. For new sources, i.e., those without reported counterparts in the literature, they considered 5-sigma detections, where sigma is the rms noise of the area around the source. For known sources with counterparts in the literature, on the other hand, they included 4-sigma detections. According to these criteria, they detected 94 sources in the Serpens molecular cloud, 41 in the W40 region, and 8 in the Serpens South cluster, for a total of 143 detections. Out of the 143 sources, 69 are new detections (see Section 3.2 of the reference paper). GBS-VLA source positions were compared with source positions from X-ray, optical, near-IR, mid-IR, and radio catalogs. GBS-VLA sources were considered to have a counterpart at another wavelength when the positional coincidences were better than the combined uncertainties of the two data sets. These were about 1 arcsecond for the IR catalogs. For the X-ray and radio catalogs it depended on the instrument and its configuration. The search was done in SIMBAD and included all the major catalogs. The authors also accessed the lists with all YSOs in the c2d-GB clouds compiled by Dunham et al.(2013, AJ, 145, 94) and L.E. Allen et al. (2015, in preparation). In total, 354 c2d-GB sources lie inside the regions observed by the present survey. In order to find their radio counterparts, the authors imaged regions of 64 pixels in each dimension, centered in the c2d-GB positions, and combining accordingly with each region, the three or two epochs. For this search, they only used the field whose phase center was closest to the source. Three additional radio sources were found in Serpens South in this pursuit, increasing the number of the radio detections to 146. This table was created by the HEASARC in October 2015 based on electronic versions of Tables 2, 3 and 6 from the reference paper, which were obtained from the CDS (Catalog J/ApJ/805/9 files table2.dat, table3.dat and table6.dat). This is a service provided by NASA HEASARC .
23757. VLA Goulds Belt Survey Taurus-Auriga Complex Source Catalog
ID:
ivo://nasa.heasarc/vlagbstau
Title:
VLA Goulds Belt Survey Taurus-Auriga Complex Source Catalog
Short Name:
VLAGBSTAU
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from a multi-epoch radio study of the Taurus-Auriga complex made with the Karl G. Jansky Very Large Array (JVLA) at frequencies of 4.5 GHz and 7.5 GHz. A total of 610 sources were detected, 59 of which are related to young stellar objects (YSOs) and 18 to field stars. The properties of 56% of the young stars are compatible with non-thermal radio emission. The authors also show that the radio emission of more evolved YSOs tends to be more non-thermal in origin and, in general, that their radio properties are compatible with those found in other star-forming regions. By comparing their results with previously reported X-ray observations, the authors noticed that YSOs in Taurus-Auriga follow a Guedel-Benz relation with a scaling factor, kappa, of 0.03, as they previously suggested for other regions of star formation. In general, YSOs in Taurus-Auriga and in all the previous studied regions seem to follow this relation with a dispersion of ~1 dex. Finally, the authors propose that most of the remaining sources are related with extragalactic objects but provide a list of 46 unidentified radio sources whose radio properties are compatible with a YSO nature (identified in this implementation of their catalog by values for the parameter radio_yso_flag of 'Y'). The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO) in its B and BnA configuration. Two frequency sub-bands, each 1 GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The observations were obtained in three different time periods (February 25/26/28 to March 6, April 12/17/20/25, and April 30 to May 1/5/14/22, all in 2011) typically separated from one another by a month: see Table 1 of the reference paper for more details. For their study, the authors observed 127 different target fields distributed across the cloud complex (Figure 1 of the reference paper). The fields were chosen to cover previously known YSOs. In 33 of those fields, the authors could observe more than one YSO target, while in the remaining 94 fields, only one YSO was targeted. In most cases, the infrared evolutionary class (i.e., Classes I, II, or III) or T Tauri evolutionary status (classical or weak line) of the targeted sources was known from the literature. The final images covered circular areas of 8.8 and 14.3 arcminutes in diameter, for the 7.5 and 4.5 GHz sub-bands, respectively, and were corrected for the effects of the position-dependent primary beam response. The noise levels reached for each individual observation was about ~40 µJy and ~30 µJy, at 4.5 GHz and7.5 GHz, respectively. The visibilities of the three, or two, observations obtained for each field were concatenated to produce a new image with a lower noise level (of about ~25 µJy at 4.5 GHz and ~18 µJy at 7.5 GHz). The angular resolution of ~1 arcsecond (see the synthesized beam sizes in Table 1 of the reference paper) allows an uncertainty in position of ~0.1 arcseconds or better. In the observed area, there are a total of 196 known YSOs.The first step was the identification of radio sources in the observed fields. The authors follow the procedure and criteria presented by Dzib et al. (2013, ApJ, 775, 63) who consider a detection as firm if the sources have a flux larger than 4 times the noise level and there is a counterpart known at another wavelength, else they require a flux which is 5 times the noise level. The identification was done using the images corresponding to the concatenation of the observed epochs, which provides the highest sensitivity. From this, a total of 609 sources were detected. Of these sources, 215 were only detected in the 4.5 GHz sub-band, while six were only detected in the 7.5 GHz sub-band. The remaining 388 sources were detected in both sub-bands. The authors searched the literature for previous radio detections, and for counterparts at X-ray, optical, near-infrared, and mid-infrared wavelengths. The search was done using SIMBAD, and accessed all the major catalogs. They considered a radio source to be associated with a counterpart at another wavelength if the separation between the two was below the combined uncertainties of the two data sets. This was about 1.0 arcsecond for the optical and infrared catalogs, but could be significantly larger for some of the radio catalogs (for instance, the NVSS has a positional uncertainty of about 5 arcseconds). They found that only 120 of the sources detected here had previously been reported at radio wavelengths, while the other 491 are new radio detections. On the other hand, the authors found a total of 270 counterparts at other wavelengths. In the literature, 18 are classified as field stars, 49 as extragalactic, 1 is classified as either a star or an extragalactic source in different surveys, 49 are classified as YSOs, 11 are classified as either YSO and extragalactic, and the remaining 143 sources are unclassified. Note that 56 sources were previously known at radio wavelengths but do not have known counterparts at other frequencies. As a consequence, the number of sources that were previously known (at any frequency) is 327, while 284 of the sources in this sample are reported here for the first time. This table was created by the HEASARC in July 2015 based on electronic versions of Tables 1, 4 and 5 from the reference paper, which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
23758. VLA Hubble Deep Field 20-cm Source Catalog
ID:
ivo://nasa.heasarc/vlahdf20cm
Title:
VLA Hubble Deep Field 20-cm Source Catalog
Short Name:
VLAHDF20CM
Date:
21 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
The authors have conducted a deep radio survey with the Very Large Array (VLA) at 1.4 GHz of a region containing the Hubble Deep Field (HDF). This survey overlaps previous observations at 8.5 GHz allowing them to investigate the radio spectral properties of microJansky sources to flux densities greater than 40 µJy (µJy) at 1.4 GHz and greater than 8 uJy at 8.5 GHz. A total of 371 sources have been catalogued at 1.4 GHz as part of a complete sample within 20 arcminutes of the HDF. The differential source count for this region is only marginally sub-Euclidean and is given by n(S) = (8.3 +/- 0.4) S^(-2.4 +/- 0.1) sr<sup>-1</sup> Jy<sup>-1</sup>. Above about 100 uJy the radio source count is systematically lower in the HDF as compared to other fields. The authors conclude that there is clustering in this radio sample on size scales of 1 to 40 arcminutes. The 1.4 GHz-selected sample shows that the radio spectral indices are preferentially steep (mean spectral index of 0.85) and that the sources are moderately extended with average angular size Theta = 1.8". Optical identification with disk-type systems at z ~ 0.1 - 1 suggests that synchrotron emission, produced by supernovae remnants, is powering the radio emission in the majority of sources. In 1996 November, the authors observed a field centered on the Hubble Deep Field (RA, Dec (J2000.0) = (12<sup>h</sup> 36<sup>m</sup> 49.4<sup>s</sup>, 62<sup>o</sup> 12' 58.00") for a total of 50 hours at 20 cm in the A configuration of the VLA. They reached an rms noise level near the center of the field of 7.5 uJy. They adopted 40 uJy as the formal completeness limit over the entire 1 degree field in their untapered naturally weighted 2 arcseconds image. The authors identified 314 sources within 20 arcminutes of the field center (20% power contour). They found 57 additional sources within this same region (presumably resolved at 2" resolution) in lower resolution (3.5 and 6") tapered images above completeness levels of 50 uJy at 3.5" resolution and 75 uJy at 6" resolution, making a grand total of 371 radio sources detected at 1.4 GHz within 20 arcminutes of the phase center of the field. This table was created by the HEASARC in June 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/533/611">CDS Catalog J/ApJ/533/611</a> file table2.dat. This is a service provided by NASA HEASARC .
23759. VLA Images of Extragalactic Objects
ID:
ivo://CDS.VizieR/J/ApJS/124/285
Title:
VLA Images of Extragalactic Objects
Short Name:
J/ApJS/124/285
Date:
21 Oct 2021
Publisher:
CDS
Description:
Maps of 212 extragalactic radio sources at 4.9 GHz are shown in Stokes I along with linear polarization vectors. The objects have a declination range of 0 degrees to -35 degrees and were chosen from the Hewitt & Burbidge quasar catalog with a spectral index less than -0.5 and the NVSS survey with a minimum 1.4 GHz flux density greater than 300 mJy. The observations were made with the Very Large Array in its B configuration, and the images have a typical resolution of 2 arcseconds. One hundred ninety-five objects were resolved; 108 of the sources are quasars, and another 51 have been identified as galaxies.
23760. VLA imaging of IRAS 1 Jy ULIRG sample
ID:
ivo://CDS.VizieR/J/A+A/409/115
Title:
VLA imaging of IRAS 1 Jy ULIRG sample
Short Name:
J/A+A/409/115
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents the results of a high resolution radio imaging survey of 83 of the 118 ultraluminous infrared galaxies (ULIRGs) in the IRAS 1Jy ULIRG sample (Kim & Sanders, 1998ApJS..119...41K, Veilleux et al., 2002, Cat. <J/ApJS/143/315>). We have observed these ULIRGs at 15-GHz with the Very Large Array (VLA). We find that ~75% of Seyferts (both type 1 and 2) and LINERs have radio nuclei which are compact at our 150mas resolution. The detection rate of HII nuclei is significantly lower (32%); the detections among these are preferentially HII+LINER/Seyfert composite nuclei. Among ULIRGs with multiple optical or near-IR nuclei our observations detected only one (or no) nucleus; in these the radio detection is typically towards the brightest near-IR nucleus. The compactness of the radio sources, the higher detection rates in AGN-type nuclei than HII nuclei, the preferential detection of nuclei with unresolved point sources in the near-IR, the low soft X-ray to nuclear radio luminosity ratio (arguing against thermal emission powering the radio nuclei), and the lack of correlation between radio power and H{alpha} luminosity, all support an origin of the detected radio nuclei in AGN related activity. This result is especially interesting for LINER ULIRGs for which signatures of AGNs have often been ambiguous in other wavebands. Such a high incidence of AGN would provide, for the first time, a large sample in which to study the interplay between AGN, starbursts, and galaxy mergers.

Limit your search

more »

more »

more »

more »

more »

more »

more »

more »