- ID:
- ivo://nasa.heasarc/lof3c29546
- Title:
- LOFAR 3C295 Field 46-MHz Source Catalog
- Short Name:
- LOF3C29546
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the source list from Low Frequency Array (LOFAR) Low Band observations of the 3C 295 field at 46 MHz. The image of this field made at 46 MHz reaches a noise level of 8 mJy beam<sup>-1</sup>, making it the deepest image ever obtained at this frequency. In total, the authors detect 367 sources in the 3C 295 46-MHz field image, covering an area of 30.5 square degrees out to a primary-beam attenuation factor of 0.4. From these and simultaneous observations made at other low-band frequencies, the authors derive Euclidean-normalized differential source counts. The 62-MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of -0.7. The authors find that a spectral index scaling of -0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. The authors also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum (alpha < -1.1) radio sources that could be associated with massive high-redshift radio galaxies, the authors compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Bootes field. They cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. They find that most of these ultra-steep spectrum sources are located in the 0.7 <~ z <~ 2.5 range. The Bootes and 3C 295 fields were simultaneously observed on 2012 April 12 as part of a multi-beam observation with the LOFAR LBA stations. The idea behind the multi-beam setup was to use the 3C 295 observations as a calibrator field to transfer the gain amplitudes to the (target) Bootes field. The pointing center of the 3C 295 field was J2000.0 RA, Dec = 14<sup>h</sup> 11<sup>m</sup> 20.9<sup>s</sup>, +52<sup>o</sup> 13' 55". The total integration time on both fields was 10.25 hr. The '46-MHz' observing band for the 3C 295 field observations was from 40 - 54 MHz, with 25 sub-bands more or less evenly distributed within this frequency range, with a total bandwidth of 4.9 MHz. The synthesized beam for this observation had dimensions of 40 arcseconds x 24 arcseconds. An overview of the observations is given in Table 1 of the reference paper, and an overview of the image characteristics in Table 2 of the reference paper. This table was created by the HEASARC in January 2015 based on some of the contents of the machine-readable version of Table 3 from the reference paper, namely the 367 entries listing sources in the 3C 295 field detected at 46 MHz. The remaining entries in this table listing the sources detected in the Bootes field at a frequency of 62 MHz. and the sources detected in the 3C295 field at frequencies of 34 and 62 MHz, are available as the HEASARC tables LOFARBF62M, LOF3C29534 and LOF3C29562, respectively. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/lof3c29534
- Title:
- LOFAR 3C295 Field 34-MHz Source Catalog
- Short Name:
- LOF3C29534
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the source list from Low Frequency Array (LOFAR) Low Band observations of the 3C 295 field at 34 MHz. The image of this field made at 34 MHz reaches a noise level of 12 mJy beam<sup>-1</sup>, making it the deepest image ever obtained at this frequency. In total, the authors detect 392 sources in the 3C 295 34-MHz field image, covering an area of 52.3 square degrees out to a primary-beam attenuation factor of 0.4. From these and simultaneous observations made at other low-band frequencies, the authors derive Euclidean-normalized differential source counts. The 62-MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of -0.7. The authors find that a spectral index scaling of -0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. The authors also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum (alpha < -1.1) radio sources that could be associated with massive high-redshift radio galaxies, the authors compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Bootes field. They cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. They find that most of these ultra-steep spectrum sources are located in the 0.7 <~ z <~ 2.5 range. The Bootes and 3C 295 fields were simultaneously observed on 2012 April 12 as part of a multi-beam observation with the LOFAR LBA stations. The idea behind the multi-beam setup was to use the 3C 295 observations as a calibrator field to transfer the gain amplitudes to the (target) Bootes field. The pointing center of the 3C 295 field was J2000.0 RA, Dec = 14<sup>h</sup> 11<sup>m</sup> 20.9<sup>s</sup>, +52<sup>o</sup> 13' 55". The total integration time on both fields was 10.25 hr. The '34-MHz' observing band for the 3C 295 field observations was from 30 - 40 MHz, with 21 sub-bands more or less evenly distributed within this frequency range, with a total bandwidth of 4.1 MHz. The synthesized beam for this observation had dimensions of 56 arcseconds x 30 arcseconds. An overview of the observations is given in Table 1 of the reference paper, and an overview of the image characteristics in Table 2 of the reference paper. This table was created by the HEASARC in January 2015 based on some of the contents of the machine-readable version of Table 3 from the reference paper, namely the 392 entries listing sources in the 3C 295 field detected at 34 MHz. The remaining entries in this table listing the sources detected in the Bootes field at a frequency of 62 MHz. and the sources detected in the 3C295 field at frequencies of 46 and 62 MHz, are available as the HEASARC tables LOFARBF62M, LOF3C29546 and LOF3C29562, respectively. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lotssprcat
- Title:
- LOFAR 2-Meter Sky Survey Preliminary Data Release Source Catalog
- Short Name:
- LOTSSPRCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky. Each of the 3,170 pointings will be observed for 8 hours, which, at most declinations, is sufficient to produce ~5-arcsec resolution images with a sensitivity of ~0.1 mJy/beam and accomplish the main scientific aims of the survey which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Due to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate sub-arcsecond imaging and spectral line studies. In this paper, The authors provide an overview of the LoTSS. They outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that they have released were created using a fully-automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. In excess of 44,000 sources are detected in the images that have a resolution of 25-arcseconds, typical noise levels of less than 0.5 mJy/beam, and cover an area of 381 square degrees in the region of the HETDEX Spring Field (Right Ascension 10<sup>h</sup> 45<sup>m</sup> 00<sup>s</sup> to 15<sup>h</sup> 30^m ^00<sup>s</sup> and Declination +45<sup>o</sup> 00' 00" to +57<sup>o</sup> 00' 00"). Source detection on the mosaics that are centered on each pointing was performed with PyBDSM (See <a href="http://www.astron.nl/citt/pybdsm/">http://www.astron.nl/citt/pybdsm/</a> for more details). In an effort to minimize contamination from artifacts, the catalog was created using a conservative 7-sigma detection threshold. Furthermore, as the artifacts are predominantly in regions surrounding bright sources, the authors utilized the PyBDSM functionality to decrease the size of the box used to calculate the local noise when close to bright sources, which has the effect of increasing the estimated noise level in these regions. Their catalogs from each mosaic are merged to create a final catalogue of the entire HETDEX Spring Field region. During this process, the authors remove multiple entries for sources by only keeping sources that are detected in the mosaic centered on the pointing to which the source is closest to the center. In the catalog, they provide the type of source, for which they used PyBDSM to distinguish isolated compact sources, large complex sources, and sources that are within an island of emission that contains multiple sources. In addition, they attempted to distinguish between sources that are resolved and unresolved in their images. The authors have provided a preliminary data release from the LOFAR Two-metre Sky Survey (LoTSS). This release contains 44,500 sources which were detected with a signal in excess of seven times the local noise in their 25" resolution images. The noise varies across the surveyed region but is typically below 0.5 mJy/beam and the authors estimate the catalog to be 90% complete for sources with flux densities in excess of 3.9 mJy/beam. This table was created by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A104">CDS Catalog J/A+A/598/A104</a> file lotss.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lofhatlas
- Title:
- LOFAR Radio Catalog of Herschel-ATLAS North Galactic Pole Field
- Short Name:
- LOFHATLAS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results of Low-Frequency Array (LOFAR) High-Band Array (HBA) observations of the Herschel-ATLAS North Galactic Pole (NGP) survey area. The survey the authors carried out, consisting of four pointings covering around 142 deg<sup>2</sup> of sky in the frequency range 126-173 MHz, does not provide uniform noise coverage but otherwise is representative of the quality of data to be expected in the planned LOFAR wide-area surveys, and has been reduced using recently developed 'facet calibration' methods at a resolution approaching the full resolution of the data sets (~10 x 6 arcsec) and an rms off-source noise that ranges from 100 µJy beam<sup>-1</sup> in the center of the best fields to around 2 mJy/beam at the furthest extent of their imaging. In the reference paper, the authors describe the imaging, cataloguing and source identification processes, and present some initial science results based on a 5-sigma source catalog. These include (i) an initial look at the radio/far-infrared correlation at 150 MHz, showing that many Herschel sources are not yet detected by LOFAR; (ii) number counts at 150 MHz, including, for the first time, observational constraints on the numbers of star-forming galaxies; (iii) the 150-MHz luminosity functions for active and star-forming galaxies, which agree well with determinations at higher frequencies at low redshift, and show strong redshift evolution of the star-forming population; and (iv) some discussion of the implications of these observations for studies of radio galaxy life cycles. The NGP field was observed in four separate pointings, chosen to maximize the area of sky covered, with the LOFAR HBA as part of the Surveys Key Science project. These observations used the HBA_DUAL_INNER mode, meaning that the station beams of core and remote stations roughly matched each other and giving the widest possible field of view. The first observation, which was made early on in LOFAR operations, was of slightly longer duration (~10 h) than the others (~8 h). International stations were included in some of the observations in 2014 but were not used in any of the authors' analysis, which uses only the Dutch array. The author were interested in imaging in several separate frequency ranges (which are referred to hereafter as 'spectral windows'), since they wanted to be able to measure in-band spectral indices for detected sources. In addition, facet calibrating in different spectral windows could be done in parallel, speeding the processing up considerably. Accordingly, they chose to facet calibrate with six spectral windows, each made up of four bands and thus containing about 8 MHz of bandwidth: <pre> Spectral Nominal Frequency Frequency Range Window (MHz) (MHz) 1 130 126 - 134 2 138 134 - 142 3 146 142 - 150 4 154 150 - 158 5 161 158 - 166 6 169 166 - 173 </pre> The final source catalog was made by combining the four per-field catalogs. Ideally, the authors would have combined the images of each field and done source finding on a mosaicked image, but this proved computationally intractable given the very large image cubes that result from having six spectral windows. They therefore merged the catalogs by identifying the areas of sky where there is overlap between the fields and choosing those sources which are measured from the region with the best rms values. This should ensure that there are no duplicate sources in the final catalog. The final master catalogue contains 17,132 sources and is derived from images covering a total of 142.7 deg<sup>2</sup> of independently imaged sky, with widely varying sensitivity. Total HBA-band (150-MHz) flux densities of catalogued sources detected using the PYBDSM software and a 5-sigma detection threshold range from a few hundred µJy to 20 Jy, with a median of 10 mJy. The authors examined all sources in the initial master catalog for associations with sources in other surveys, for rejection as artifacts, and for optical identifications, as described in detail in Section 3.5 of the reference paper. The final outcomes of this process were (a) an associated, artifact-free catalog of 15,292 sources, all of which the authors believe to be real physical objects which is contained in the present HEASARC table, and (b) a catalog of 6,227 objects with plausible, single optical identifications with Sloan Digital Sky Survey (SDSS) sources, representing an identification fraction of just over 40 per cent. (Note that around 50 sources with more than one equally plausible optical identification are excluded from this catalog; further observation would be required to disambiguate these sources). This table was created by the HEASARC in April 2018, based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/462/1910">CDS Catalog J/MNRAS/462/1910</a> file tablea1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lorcat
- Title:
- Low-Frequency Radio Catalog of Flat-Spectrum Sources
- Short Name:
- LORCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- A well-known property of the gamma-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi Gamma-ray Observatory is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio/gamma-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with gamma-ray blazars is that they show a flat spectrum in the GHz frequency range. The authors' recent analysis dedicated to search for blazar-like candidates as potential counterparts for the unidentified gamma-ray sources allowed them to extend the radio/gamma-ray connection in the MHz regime. They also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, the authors have assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey (WENSS) and of the Westerbork in the southern hemisphere (WISH) catalogs with those of the NRAO Very Large Array Sky survey (NVSS). This catalog could be used in the future to search for new, unknown blazar-like counterparts of gamma-ray sources. First, the authors found NVSS counterparts of Westerbork Synthesis Radio Telescope (WSRT) radio sources, and then they selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. In their paper, they also describe the main properties of the catalog listing 28,358 radio sources with spectral indices between 1400 and 325/352 MHz between -1.0 and +0.4, and their log N - log S distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed so as to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies. This table was created by the HEASARC in July 2014 based on a machine-readable version of Table 1 from the reference paper which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mwmc
- Title:
- Milky Way Molecular Clouds from CO Measurements
- Short Name:
- MWMC
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This study presents a catalog of 8107 molecular clouds that covers the entire Galactic plane and includes 98% of the <sup>12</sup>CO emission observed within b +/- 5 deg. The catalog was produced using a hierarchical cluster identification method applied to the result of a Gaussian decomposition of the Dame+ (2001ApJ...547..792D) data. The total H<sub>2</sub> mass in the catalog is 1.2 x 10<sup>9</sup> M<sub>sun</sub>, in agreement with previous estimates. The authors find that 30% of the sight lines intersect only a single cloud, with another 25% intersecting only two clouds. The most probable cloud size is R~30pc. In contrast with the general idea, the authors find a rather large range of values of surface densities, Sigma = 2 to 300 M<sub>sun</sub>/pc<sup>2</sup>, and a systematic decrease with increasing Galactic radius, R<sub>gal</sub>. The cloud velocity dispersion and the normalization sigma<sub>0</sub> = sigma<sub>v</sub> / R<sup>1/2</sup> both decrease systematically with R<sub>gal</sub>. When studied over the whole Galactic disk, there is a large dispersion in the line width-size relation and a significantly better correlation between sigma<sub>v</sub> and SigmaR. The normalization of this correlation is constant to better than a factor of two for R<sub>gal</sub> < 20kpc. This relation is used to disentangle the ambiguity between near and far kinematic distances. The authors report a strong variation of the turbulent energy injection rate. In the outer Galaxy it may be maintained by accretion through the disk and/or onto the clouds, but neither source can drive the 100 times higher cloud-averaged injection rate in the inner Galaxy. The data set used in this catalog come from that of Dame+ (2001ApJ...547..792D). Those authors combined observations obtained over a period of 20 yr with two telescopes, one in the north (first located in New York City and then moved to Cambridge, Massachusetts) and one in the south (Cerro Tololo, Chile). These 1.2m telescopes have an angular resolution of ~8.5' at 115GHz, the frequency of the <sup>12</sup>CO 1-0 line. For the current study the authors used the data set covering the whole Galactic plane with +/- 5 deg in Galactic latitude. This table was created by the HEASARC in March 2019 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/834/57">CDS Catalog J/ApJ/834/57</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mitgb6cm
- Title:
- MIT-Green Bank 5-GHz Survey Catalog
- Short Name:
- MIT-GB
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The MIT-Green Bank 5 GHz Survey Catalog was produced from four separate surveys with the National Radio Astronomy Observatory (NRAO) 91m transit telescope, the results from which were presented in papers by Bennett et al., 1986ApJS...61....1B (MG1), Langston et al., 1990ApJS...72..621L (MG2), Griffith et al., 1990ApJS...74..129G (MG3), and Griffith et al. 1991ApJS...75..801G (MG4). The sky coverage of the various surveys is: <pre> 00h < RAB < 24h, -00d30'13" < DECB < +19d29'47" for MG1 04h < RAJ < 21h, +17.0d < DECJ < +39d09' for MG2 16h30m < RAB < 05h, +17d < DECB < +39d09' for MG3 15h30m < RAB < 02h30m, +37.00d < DECB < +50d58'48" for MG4 </pre> where RAB and DECB refer to B1950 coordinates, and RAJ and DECJ refer to J2000 coordinates. The catalog contains 20344 sources detected with a signal-to-noise ratio greater than 5 and 3836 possible detections (MG1) with a signal-to-noise ratio less than 5. Spectral indices are computed for MG1 sources also identified in the Texas 365 MHz survey (Douglas et al. 1980, Univ. Texas Pub. Astr. No. 17), and for MG1-MG4 sources also identified in the NRAO 1400 MHz Survey (Condon and Broderick 1985, AJ, 90, 2540 = 1985AJ.....90.2540C). This online catalog was created by the HEASARC in October 2003 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/52B">CDS catalog VIII/52B</a> (the file mgcat.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mgps2
- Title:
- Molonglo Galactic Plane Survey 2nd Epoch Compact Source Catalog
- Short Name:
- MGPS2
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Molonglo Galactic Plane Survey 2nd Epoch (MGPS-2) Compact Source Catalog. The MGPS-2 was carried out with the Molonglo Observatory Synthesis Telescope (MOST) at a frequency of 843 MHz and with a restoring beam of 45" x 45" cosec |(delta)|, where delta is the declination, making it the highest resolution large-scale radio survey of the southern Galactic plane to date. It covers the range |b| < 10 degrees and 245 < l < 365 degrees, where l and b are the Galactic longitude and latitude, and is the Galactic counterpart to the SUMSS (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/81">CDS Cat. VIII/81</a>) Catalog which covers that portion of the southern sky with delta < -30 degrees, |b| > 10 degrees. This version of the catalog (15-Aug-2007) consists of 48850 compact sources, made by fitting elliptical Gaussians in the MGPS-2 mosaics to a limiting peak brightness of 10 mJy/beam. The authors used a custom method (described in the associated reference publication) to remove extended sources from the catalog. Positions in the catalog are accurate to 1" - 2". The authors have carried out an analysis of the compact source density across the Galactic plane and find that the source density is not statistically higher than the density expected from the extragalactic source density alone. See <a href="http://www.astrop.physics.usyd.edu.au/mosaics">http://www.astrop.physics.usyd.edu.au/mosaics</a> for access to the MGPS-2 mosaic images. This HEASARC table was created in January 2008 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/382/382">CDS catalog J/MNRAS/382/382</a> file mgpscat.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mostatlas
- Title:
- Molonglo Observatory Synthesis Telescope ATLAS 843-MHz Source Catalog
- Short Name:
- MOSTATLAS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- At the faintest radio flux densities (S<sub>1.4</sub> < 10 mJy), conflicting results have arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz) and, for example, 1.4 GHz. The authors present a new catalog of 843-MHz radio sources in the European Large Area ISO Survey-South 1 (ELAIS-S1) field, which contains the sources, their Australia Telescope Large Area Survey (ATLAS) counterparts and the spectral index distribution of the sources as a function of flux density. The authors do not find any statistically significant evidence for a trend towards flatter spectral indices with decreasing flux density. In the reference paper, they investigate the spectral index distribution with redshift for those sources with reliable redshifts and explore the infrared properties. An initial sample of faint compact steep-spectrum sources in ATLAS are also presented, with a brief overview of their properties. To obtain low-radio-frequency (843-MHz) data within the ATLAS ELAIS-S1 region (Middelberg et al. 2008, AJ, 135, 1276, the tables from which are available as the ATLASESID and ATLASESCPT tables in the HEASARC database), the authors used the Molonglo Observatory Synthesis Telescope (MOST). They have made 31 separate 12-h observations taken with MOST, which were combined into a single image with a spatial resolution of 62 arcsec x 43 arcsec. This table was created by the HEASARC in January 2013 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/421/1644">CDS Catalog J/MNRAS/421/1644</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mrc
- Title:
- Molonglo Reference Catalog of Radio Sources
- Short Name:
- MRC
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog is a version of the 1990 issue of the "Molonglo Reference Catalog of Radio Sources" (MRC). The MRC is one of the largest homogeneous catalogs of radio sources, containing 12,141 discrete sources with flux densities greater than 0.7 Jy in the declination range +18.5 degrees to -85 degrees (1950 coordinates) and excluding regions within 3 degrees of the Galactic equator. This is a service provided by NASA HEASARC .
