- ID:
- ivo://CDS.VizieR/J/ApJ/831/168
- Title:
- 6GHz JVLA observations of low-z SDSS quasars
- Short Name:
- J/ApJ/831/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss 6GHz JVLA observations covering a volume-limited sample of 178 low-redshift (0.2<z<0.3) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of L_6_>~10^23.2^W/Hz that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have 10^21^<~L_6_<~10^23.2^W/Hz and radio sizes <~10kpc, and we suggest that the bulk of their radio emission is powered by star formation in their host galaxies. "Radio-silent" QSOs (L_6_<~10^21^W/Hz) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not "red and dead" ellipticals. Earlier radio observations did not have the luminosity sensitivity of L_6_<~10^21^W/Hz that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning >>10kpc was found to be associated with 13 of the 18 RLQ cores with peak flux densities of S_p_>5mJy/beam (log(L)>~24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio-loud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/419/71
- Title:
- 1.4GHz obs. and optical ident. in A3558
- Short Name:
- J/A+A/419/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Very Large Array (VLA) 1.4GHz (21cm) observations of the region between the centres of A3558 and A3562, in the major cluster merger complex of the Shapley Concentration. Our final catalogue includes a total of 174 radio sources above the flux density limit of 0.25 mJy/b. By cross-correlation with optical and spectroscopic catalogues we found 33 optical counterparts belonging to the Shapley Concentration.
- ID:
- ivo://CDS.VizieR/J/AJ/142/3
- Title:
- 1.4GHz observations of Stripe 82
- Short Name:
- J/AJ/142/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution radio survey of the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a.k.a. Stripe 82. This 1.4GHz survey was conducted with the Very Large Array primarily in the A-configuration, with supplemental B-configuration data to increase sensitivity to extended structure. The survey has an angular resolution of 1.8" and achieves a median rms noise of 52{mu}Jy/beam over 92deg^2^. This is the deepest 1.4GHz survey to achieve this large of an area, filling a gap in the phase space between small, deep and large, shallow surveys. It also serves as a pilot project for a larger high-resolution survey with the Expanded Very Large Array. We discuss the technical design of the survey and details of the observations, and we outline our method for data reduction. We present a catalog of 17969 isolated radio components, for an overall source density of ~195sources/deg^2^. The astrometric accuracy of the data is excellent, with an internal check utilizing multiply observed sources yielding an rms scatter of 0.19" in both right ascension and declination. A comparison to the SDSS-DR7 Quasar Catalog further confirms that the astrometry is well tied to the optical reference frame, with mean offsets of 0.02+/-0.01" in right ascension, and 0.01+/-0.02" in declination. A check of our photometry reveals a small, negative CLEAN-like bias on the level of 35{mu}Jy. We report on the catalog completeness, finding that 97% of FIRST-detected quasars are recovered in the new Stripe 82 radio catalog, while faint, extended sources are more likely to be resolved out by the resolution bias. We conclude with a discussion of the optical counterparts to the catalog sources, including 76 newly detected radio quasars.
- ID:
- ivo://CDS.VizieR/J/PAZh/22/269
- Title:
- Giant branch and variable stars in NGC 3201
- Short Name:
- J/PAZh/22/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate equatorial coordinates have been determined for variable stars in the globular cluster NGC 3201. Results of photographic BV photometry are presented.
- ID:
- ivo://CDS.VizieR/J/ApJS/253/25
- Title:
- Giant radio quasars from SDSS, FIRST & NVSS
- Short Name:
- J/ApJS/253/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest sample of giant radio quasars (GRQs), which are defined as having a projected linear size greater than 0.7Mpc. The sample consists of 272 GRQs, of which 174 are new objects discovered through cross-matching the NRAO Very Large Array Sky Survey and the Sloan Digital Sky Survey 14th Data Release Quasar Catalog (DR14Q) and confirmed using Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio maps. In our analysis we compare the GRQs with 367 smaller, lobe-dominated radio quasars found using our search method, as well as with quasars from the SDSS DR14Q, investigating the parameters characterizing their radio emission (i.e., total and core radio luminosity, radio core prominence), optical properties (black hole masses, accretion rates, distribution in Eigenvector 1 plane) and infrared colors. For the GRQs and smaller radio quasars we find a strong correlation between [OIII] luminosity and radio luminosity at 1.4GHz, indicating a strong connection between radio emission and conditions in the narrow-line region. We spot no significant differences between GRQs and smaller radio quasars, however we show that most extended radio quasars belong to a quasar population of evolved active galactic nuclei with large black hole masses and low accretion rates. We also show that GRQs have bluer W2-W3 colors compared to SDSS quasars with FIRST detections, indicating differences in the structure of the dusty torus.
1366. Giants DDO photometry
- ID:
- ivo://CDS.VizieR/J/AJ/100/1191
- Title:
- Giants DDO photometry
- Short Name:
- J/AJ/100/1191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of G and K giants approximately 4kpc from the Sun, covering the abundance range from solar to extreme halo has been selected without kinematic bias in a field aligned to measure galactic rotation. Accurate abundances, distances, and radial velocities have been measured. This sample has been combined with nonkinematically selected solar neighborhood objects taken from the literature, in order to examine the kinematics of the transition from disk to "thick disk" to halo. The metal-rich objects in the sample, with 0>[Fe/H]>-0.8, rotate rapidly around the galactic center and have low azimuthal velocity dispersion, {sigma}_{phi}_=40+/-10km/s. For objects in the range -0.5>[Fe/H]>-0.8, we find a small value for the asymmetric drift of 35+/-10km/s. We associate these objects with the thick disk, confirming the kinematical results of Ratnatunga and Freeman (1989, Cat.<V/65>) and others. In the abundance range -1.0>[Fe/H]>=-1.6 we find, in addition to objects with normal halo kinematics, objects in a disk configuration, confirming the results of Norris, Bessell, and Pickles (1985ApJS...58..463N). This disk is rotating rapidly, V_rot_=170+/-15km/s, and has a scale height of 1.4+/-0.7kpc, these kinematical and spatial properties are similar to those of the thick disk. We show that these objects have different kinematics from that of the globular clusters and a sample of local RR Lyraes in the same abundance range. This suggests to us that these objects are better associated with the thick disk than the halo, and we refer to them as "metal-weak thick-disk stars". Hence we suggest that the conventional chemical description of the thick disk (Gilmore and Wyse, 1985AJ.....90.2015G) be widened to include stars with abundances as low as [Fe/H]=-1.6. At the galactic plane, the density of these metal-weak thick-disk stars is similar to that of halo stars, so they significantly affect the measurement, from samples selected on abundance, of the components of the velocity ellipsoid for the halo in the solar neighborhood. For the halo giants in our sample we measure {sigma}_{phi}_=102+/-24 and V_rot_=17+/-24km/s. The rotation velocity and velocity ellipsoid for the metal-weak halo in the solar neighborhood have been rederived for objects with [Fe/H]<=-1.6 from the large sample of Norris (1986ApJS...61..667N), thus removing the possibility of contamination by metal-weak thick-disk stars. We derive V_rot_=25+/-15km/s and ({sigma}_r_, {sigma}_{phi}_, {sigma}_{theta}_)=(133+/-8, 98+/-13, 94+/-6)km/s. These values are more consistent with other information about the shape of the halo. For a description of the DDO photometric system, see e.g. <GCPD/12>
- ID:
- ivo://CDS.VizieR/J/A+A/577/A59
- Title:
- g'i' photometry in 5 isolated elliptical galaxies
- Short Name:
- J/A+A/577/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As tracers of star formation, galaxy assembly and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS g'i' observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271 and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of them, remaining inconclusive for the other two. All the studied GCSs are rather poor with a mean specific frequency S_N_~1.5, independently of the parent galaxy luminosity. Considering also previous work, it is clear that bimodality and especially the presence of a significant, even dominant, population of blue clusters occurs at even the most isolated systems, casting doubts on a possible accreted origin of metal-poor clusters as suggested by some models. Additionally, we discuss the possible existence of ultra-compact dwarfs around the isolated elliptical NGC 3962.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/3702
- Title:
- gi photometry of Bootes I
- Short Name:
- J/MNRAS/461/3702
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep stellar photometry of the Bootes I dwarf spheroidal galaxy in g- and i-band filters, taken with the Dark Energy Camera at Cerro Tololo in Chile. Our analysis reveals a large, extended region of stellar substructure surrounding the dwarf, as well as a distinct overdensity encroaching on its tidal radius. A radial profile of the Bootes I stellar distribution shows a break radius indicating the presence of extra-tidal stars. These observations strongly suggest that Bootes I is experiencing tidal disruption, although not as extreme as that exhibited by the Hercules dwarf spheroidal. Combined with revised velocity dispersion measurements from the literature, we see evidence suggesting the need to review previous theoretical models of the Bootes I dwarf spheroidal galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/1425
- Title:
- gi photometry of 14 LMC star clusters
- Short Name:
- J/MNRAS/444/1425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Gemini South GMOS g, i photometry of 14 intermediate-age Large Magellanic Cloud (LMC) star clusters, namely: NGC 2155, 2161, 2162, 2173, 2203, 2209, 2213, 2231, 2249, Hodge 6, SL 244, 505, 674, and 769, as part of a continuing project to investigate the extended main-sequence turn-off (EMSTO) phenomenon. Extensive artificial star tests were made over the observed field of view. These tests reveal the observed behaviour of photometric errors with magnitude and crowding. The cluster stellar density radial profiles were traced from star counts over the extent of the observed field. We adopt cluster radii and build colour-magnitude diagrams (CMDs) with cluster features clearly identified. We used the cluster (g, g-i) CMDs to estimate ages from the matching of theoretical isochrones. The studied LMC clusters are confirmed to be intermediate-age clusters, which range in age 9.10<log(t)<9.60. NGC 2162 and NGC 2249 look like new EMSTO candidates, in addition to NGC 2209, on the basis of having dual red clumps.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/30
- Title:
- gi photometry of Sextans dSph galaxy stars
- Short Name:
- J/MNRAS/460/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field g- and i-band stellar photometry of the Sextans dwarf spheroidal galaxy and its surrounding area out to four times its half-light radius (r_h_=695pc), based on images obtained with the Dark Energy Camera at the 4-m Blanco telescope at CTIO. We find clear evidence of stellar substructure associated with the galaxy, extending to a distance of 82-arcmin (2kpc) from its centre. We perform a statistical analysis of the overdensities and find three distinct features, as well as an extended halo-like structure, to be significant at the 99.7 per cent confidence level or higher. Unlike the extremely elongated and extended substructures surrounding the Hercules dwarf spheroidal galaxy, the overdensities seen around Sextans are distributed evenly about its centre, and do not appear to form noticeable tidal tails. Fitting a King model to the radial distribution of Sextans stars yields a tidal radius r_t_=83.2-arcmin+/-7.1 arcmin (2.08+/-0.18kpc), which implies the majority of detected substructure is gravitationally bound to the galaxy. This finding suggests that Sextans is not undergoing significant tidal disruption from the Milky Way, supporting the scenario in which the orbit of Sextans has a low eccentricity.
