- ID:
- ivo://CDS.VizieR/J/A+AS/74/315
- Title:
- 327 MHz Survey of the A262 cluster region
- Short Name:
- J/A+AS/74/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains a survey at 327 MHz of the A262 cluster region. The survey was performed with the WSRT Telescope in the redundancy mode, and covers a circular region of 21 square degrees towards A262 (RA = 01h49m50s, decl = 35d54'20" -- B1950). The synthesized beam width is 56" x 93" (RA x DEC). 309 sources were detected, with a detection limit of 7 mJy (~5 sigma) at the field center. Nine of these galaxies have been identified with galaxies of the A262 cluster.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/581/L5
- Title:
- Mid-IR/radio correlation for Ghat galaxies
- Short Name:
- J/A+A/581/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wright et al. (2014ApJ...792...26W) have embarked on a search for advanced Karadashev Type III civilisations via the compilation of a sample of sources with extreme mid-IR emission and colours. The aim is to furnish a list of candidate galaxies that might harbour an advanced Kardashev Type III civilisation; in this scenario, the mid-IR emission is then primarily associated with waste heat energy by-products. I apply the mid-IR radio correlation to this Glimpsing Heat from Alien Technology (Ghat) sample, a catalogue of 93 candidate galaxies compiled by Griffith et al., 2015ApJS..217...25G. I demonstrate that the mid-IR and radio luminosities are correlated for the sample, determining a k-corrected value of q_22_=1.35+/-0.42 . By comparison, a similar measurement for 124 galaxies drawn from the First Look Survey (FLS) has q_22_=0.87+/-0.27. The statistically significant difference of the mean value of q_22_ for these two samples, taken together with their more comparable far-IR properties, suggests that the Ghat sample shows excessive emission in the mid-IR. The fact that the Ghat sample largely follows the mid-IR radio correlation strongly suggests that the vast majority of these sources are associated with galaxies in which natural astrophysical processes are dominant. This simple application of the mid-IR radio correlation can substantially reduce the number of false positives in the Ghat catalogue since galaxies occupied by advanced Kardashev Type III civilisations would be expected to exhibit very high values of q. I identify nine outliers in the sample with q_22_>2 of which at least three have properties that are relatively well explained via standard astrophysical interpretations e.g. dust emission associated with nascent star formation and/or nuclear activity from a heavily obscured AGN. The other outliers have not been studied in any great detail, and are deserving of further observation. I also note that the comparison of resolved mid-IR and radio images of galaxies on sub-galactic (kpc) scales can also be useful in identifying and recognising artificial mid-IR emission from less advanced intermediate Type II/III civilisations. Nevertheless, from the bulk properties of the Ghat sample, I conclude that Kardashev Type III civilisations are either very rare or do not exist in the local Universe.
- ID:
- ivo://CDS.VizieR/J/A+AS/102/611
- Title:
- Millimeter continuum of extragal. sources III.
- Short Name:
- J/A+AS/102/611
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
274. M87 jet VLBI images
- ID:
- ivo://CDS.VizieR/J/A+A/616/A188
- Title:
- M87 jet VLBI images
- Short Name:
- J/A+A/616/A188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Messier 87 (M87) is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc scales. Because of its proximity and the large mass of its central black hole (BH), it is one of the best radio sources for the study of jet formation. We study the physical conditions near the jet base at projected separations from the BH of ~7-100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA) observations at 86GHz ({lambda}=3.5mm) provide an angular resolution of ~50{mu}arcsec, which corresponds to a spatial resolution of only 7Rsch and reach the small spatial scale. We use five GMVA data sets of M87 obtained from 2004 to 2015 and present new high angular resolution VLBI maps at 86GHz. In particular, we focus on the analysis of the brightness temperature, the jet ridge lines, and the ratio of jet to counter-jet. The imaging reveals a parabolically expanding limb-brightened jet which emanates from a resolved VLBI core of ~(8-13)Rsch in size. The observed brightness temperature of the core at any epoch is ~(1-3)x10^10^K, which is below the equipartition brightness temperature and suggests magnetic energy dominance at the jet base. We estimate the diameter of the jet at its base to be ~5Rsch assuming a self-similar jet structure. This suggests that the sheath of the jet may be anchored in the very inner portion of the accretion disk. The image stacking reveals faint emission at the center of the edge-brightened jet on sub-pc scales. We discuss its physical implication within the context of the spine-sheath structure of the jet.
- ID:
- ivo://CDS.VizieR/J/ApJS/103/331
- Title:
- mJy radio sources at 1.4 GHz
- Short Name:
- J/ApJS/103/331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From the 1.4GHz radio survey of Condon, Dickey, & Salpeter (Cat. <J/AJ/99/1071>) in a region much devoid of rich galaxy clusters at redshifts z<0.43 we selected a "distant" sample of 57 radio sources complete to a 1.4GHz flux density of 35mJy and a "nearby" sample of 36 mostly weaker radio sources which are optically brighter than B~19mag. Our ultimate goals are (1) to study the radio, optical, and near-IR properties of those high-redshift (z~1), moderate-power radio sources in the distant sample and to compare them with that of more powerful radio sources, and (2) to make a comparison of primarily noncluster radio sources in the nearby sample with a companion survey of radio sources in a pair of rich superclusters at z~0.1. In this first paper of a series, we report our new C-array VLA continuum snapshots at 4.86GHz and optical R-band CCD imaging photometry for these two samples and tabulate the observational results on individual sources. Some direct sample statistical properties are also discussed in the paper and summarized as follows: (1) The distant sample: (a) The sample median flux density at 1.4GHz is about 65mJy. (b) The majority (80%) of the sample sources have a steep spectrum between 1.4 and 4.86GHz with a spectral index around 0.9. Nineteen (90%) of the 21 sources that are fully resolved at 4.86 GHz (i.e., angular sizes {theta}>11") have a radio morphology of Fanaroff-Riley (FR) II type. (c) Thirty-seven (88%) of the 42 optically imaged sample sources were optically identified to a limiting R-band magnitude of R~23.5mag. About 15% of the identified radio sources appear to be point sources, and the others are extended galaxies with an appearance similar to nearby elliptical galaxies. (d) Twenty-eight (76%) of the optically identified sources have R>20mag, suggesting that these are probably distant (z>0.8), with a redshift distribution peaking at z~1, where their radio luminosities are about 10 times the break power between the FR I and II classes. (e) We found no strong evidence for the radio and optical axes of the resolved radio sources (i.e., {theta}>5") to be correlated or anticorrelated, nor any evidence for strong clustering around sample radio sources on average. (2) The nearby sample: except for R<15, the sample is dominated by elliptical galaxies with 16<R<18.5mag and a spectral index distribution similar to that of the distant sample. Based on the radial distribution of optical objects around each radio source, we found that the average radio source environment becomes richer from that characteristic of galaxy groups for R<17mag (z<0.2) to that of galaxy groups to clusters at R>18mag (z>0.3) .
- ID:
- ivo://CDS.VizieR/J/A+A/579/A101
- Title:
- 3mm molecular line survey of 8 AGN
- Short Name:
- J/A+A/579/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim for a better understanding of the imprints that the nuclear activity in galaxies leaves in the molecular gas. We used the IRAM 30m telescope to observe the frequency range ~[86-116]GHz towards the central regions of the star- burst galaxies M83, M82, and NGC253, the galaxies hosting an active galactic nucleus (AGN) M51, NGC1068, and NGC7469, and the ultra-luminous infrared galaxies (ULIRGs) Arp220 and Mrk231. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of 27 molecules and 10 isotopologues (or their upper limits in case of non-detections).
- ID:
- ivo://CDS.VizieR/J/AJ/147/143
- Title:
- MOJAVE. XI. Spectral distributions
- Short Name:
- J/AJ/147/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the Monitoring of Jets in Active Galactic Nuclei with the VLBA Experiments (MOJAVE) project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4GHz, and we have determined spectral index maps between 8.1 and 15.4GHz to study the four-frequency spectrum in individual jet features. We have performed detailed simulations to study the effects of image alignment and (u, v)-plane coverage on the spectral index maps to verify our results. We use the spectral index maps to study the spectral index evolution along the jet and determine the spectral distributions in different locations of the jets. The core spectral indices are on average flat with a mean value of +0.22+/-0.03 for the sample, while the jet spectrum is in general steep with a mean index of -1.04+/-0.03. A simple power-law fit is often inadequate for the core regions, as expected if the cores are partially self-absorbed. The overall jet spectrum steepens at a rate of about -0.001 to -0.004 per deprojected parsec when moving further out from the core with flat spectrum radio quasars having significantly steeper spectra (mean -1.09+/-0.04) than the BL Lac objects (mean -0.80+/-0.05). However, the spectrum in both types of objects flattens on average by ~0.2 at the locations of the jet components indicating particle acceleration or density enhancements along the jet. The mean spectral index at the component locations of -0.81+/-0.02 corresponds to a power-law index of ~2.6 for the electron energy distribution. We find a significant trend that jet components with linear polarization parallel to the jet (magnetic field perpendicular to the jet) have flatter spectra, as expected for transverse shocks. Compared to quasars, BL Lacs have more jet components with perpendicular magnetic field alignment, which may explain their generally flatter spectra. The overall steepening of the spectra with distance can be explained with radiative losses if the jets are collimating or with the evolution of the high-energy cutoff in the electron spectrum if the jets are conical. This interpretation is supported by a significant correlation with the age of the component and the spectral index, with older components having steeper spectra.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/4992
- Title:
- MOJAVE XIV. AGN jet shapes & opening angles
- Short Name:
- J/MNRAS/468/4992
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 15 GHz stacked VLBA images of 373 jets associated with active galactic nuclei (AGN) having at least 5 observing epochs within a 20yr time interval 1994-2015 from the MOJAVE programme and/or its precursor, the 2 cm VLBA Survey. These data are supplemented by 1.4 GHz single-epoch VLBA observations of 135 MOJAVE AGNs to probe larger scale jet structures. The typical jet geometry is found to be close to conical on scales from hundreds to thousands of parsecs, while a number of galaxies show quasi-parabolic streamlines on smaller scales. A true jet geometry in a considerable fraction of AGNs appears only after stacking epochs over several years. The jets with significant radial accelerated motion undergo more active collimation. We have analyzed total intensity jet profiles transverse to the local jet ridgeline and derived both apparent and intrinsic opening angles of the flows, with medians of 21.5{deg} and 1.3{deg}, respectively. The Fermi LAT-detected gamma-ray AGNs in our sample have, on average, wider apparent and narrower intrinsic opening angle, and smaller viewing angle than non LAT-detected AGNs. We have established a highly significant correlation between the apparent opening angle and gamma-ray luminosity, driven by Doppler beaming and projection effects.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/43
- Title:
- MOJAVE. XVII. Parsec-scale jet kinematics of AGNs
- Short Name:
- J/ApJ/874/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a parsec-scale jet kinematics study of 409 bright radio-loud active galactic nuclei (AGNs) based on 15GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2016 December 26 as part of the 2cm VLBA survey and Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) programs. We tracked 1744 individual bright features in 382 jets over at least 5 epochs. A majority (59%) of the best-sampled jet features showed evidence of accelerated motion at the >3{sigma} level. Although most features within a jet typically have speeds within ~40% of a characteristic median value, we identified 55 features in 42 jets that had unusually slow pattern speeds, nearly all of which lie within 4pc (100pc deprojected) of the core feature. Our results, combined with other speeds from the literature, indicate a strong correlation between apparent jet speed and synchrotron peak frequency, with the highest jet speeds being found only in low-peaked AGNs. Using Monte Carlo simulations, we find best-fit parent population parameters for a complete sample of 174 quasars above 1.5Jy at 15GHz. Acceptable fits are found with a jet population that has a simple unbeamed power-law luminosity function incorporating pure luminosity evolution and a power-law Lorentz factor distribution ranging from 1.25 to 50 with slope -1.4+/-0.2. The parent jets of the brightest radio quasars have a space density of 261+/-19Gpc^-3^ and unbeamed 15GHz luminosities above ~10^24.5^W/Hz, consistent with FRII class radio galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/136
- Title:
- Molecular clouds in the Antennae from CO(2-1)
- Short Name:
- J/ApJ/750/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Super star clusters--extremely massive clusters found predominately in starburst environments--are essential building blocks in the formation of galaxies and thought to dominate star formation in the high-redshift universe. However, the transformation from molecular gas into these ultracompact star clusters is not well understood. To study this process, we used the Submillimeter Array and the Plateau de Bure Interferometer to obtain high angular resolution (~1.5" or 160pc) images of the Antennae overlap region in CO(2-1) to search for the molecular progenitors of the super star clusters. We resolve the molecular gas distribution into a large number of clouds, extending the differential cloud mass function down to a 5{sigma} completeness limit of 3.8x10^5^M_{sun}_. We identify a distinct break in the mass function around log M_mol_/M_{sun}_{approx}6.5, which separates the molecular clouds into two distinct populations. The smaller, less massive clouds reside in more quiescent areas in the region, while the larger, more massive clouds cluster around regions of intense star formation. A broken power-law fit to the mass function yields slopes of {alpha}=-1.39+/-0.10 and {alpha}=-1.44+/-0.14 for the low- and high-mass cloud population, well matched to the mass function found for super star clusters in the Antennae galaxies. We find large velocity gradients and velocity dispersions at the locations of intense star formation, suggestive of compressive shocks. It is likely that these environmental factors contribute to the formation of the observed massive molecular clouds and super star clusters in the Antennae galaxies.
