- ID:
- ivo://CDS.VizieR/J/ApJS/128/17
- Title:
- VLBA obs. of radio reference frame sources. III.
- Short Name:
- J/ApJS/128/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present simultaneous dual-frequency Very Long Baseline Array 2 and 8 GHz observations of 225 of the 560 extragalactic sources for which positions were reported by Johnston and coworkers and which are now part of the International Celestial Reference Frame. These observations represent the third and final in a series of observations intended to obtain single-epoch images of the entire set of sources presented by Johnston and coworkers (1995, Cat. <J/AJ/110/880>) and, together with previously reported observations, bring the total number of sources observed to 389. As with previous papers in this series, we use these data to quantify the magnitude of the expected effect of intrinsic source structure on astrometric bandwidth synthesis Very Long Baseline Interferometry observations and to calculate a source "structure index" for the observed sources. The structure index can be used as an estimate of the astrometric quality of the sources. Based on this indicator, correlations between the observed radio structure and the astrometric position accuracy and stability of the sources have been found. These correlations indicate that the more extended sources have larger position uncertainties and are less positionally stable than the more compact sources.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/464/666
- Title:
- Void Galaxy Survey, photometry and structure
- Short Name:
- J/MNRAS/464/666
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse photometry from deep B-band images of 59 void galaxies in the Void Galaxy Survey (VGS), together with their near-infrared 3.6{mu}m and 4.5{mu}m Spitzer photometry. The VGS galaxies constitute a sample of void galaxies that were selected by a geometric-topological procedure from the Sloan Digital Sky Survey Data Release 7 data release, and which populate the deep interior of voids. Our void galaxies span a range of absolute B-magnitude from M_B_=-15.5 to -20, while at the 3.6{mu}m band their magnitudes range from M_3.6_=-18 to -24. Their B-[3.6] colour and structural parameters indicate these are star-forming galaxies. A good reflection of the old stellar population, the near-infrared band photometry also provide a robust estimate of the stellar mass, which for the VGS galaxies we confirm to be smaller than 3x10^10^M_{sun}_. In terms of the structural parameters and morphology, our findings align with other studies in that our VGS galaxy sample consists mostly of small late-type galaxies. Most of them are similar to Sd-Sm galaxies, although a few are irregularly shaped galaxies. The sample even includes two early-type galaxies, one of which is an AGN. Their Sersic indices are nearly all smaller than n=2 in both bands and they also have small half-light radii. In all, we conclude that the principal impact of the void environment on the galaxies populating them mostly concerns their low stellar mass and small size.
- ID:
- ivo://CDS.VizieR/J/other/NewA/11.293
- Title:
- Warped disks in spiral galaxies
- Short Name:
- J/other/NewA/11.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed the disk morphologies of 325 edge-on galaxies to derive the warp statistics in spiral galaxies using Digital Sky Survey. Galaxies were included in our study if their isophotal diameter (D25) satisfied logD25>1, and if their major-to-minor axis ratio was in the range a/b>9.5. We found that 236 out of the 325 sample galaxies (73%) had warps: 165 S-shaped (51%) and 71 U-shaped (22%). We additionally found that the warp properties (warp angles, warp radius, and warp asymmetry) as well as the warp frequency did not depend on galaxy morphology. A quite tight anticorrelation was observed between warp radius and warp amplitude, and a positive correlation was found between warp asymmetry and warp amplitude. A detailed analysis of the relations between warp parameters and galaxy properties revealed that strong warps are mostly caused by tidal interactions, whereas weak warps are formed by a variety of mechanisms including gas accretion. The present results indicate that the fractional warp radius coupled with warp angles representing the warp amplitude and warp curvature provide useful diagnostic indicators of the origin of warps.
- ID:
- ivo://CDS.VizieR/J/A+A/399/457
- Title:
- Warps in southern hemisphere galaxies
- Short Name:
- J/A+A/399/457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of optical warps of galaxies is presented. This can be considered complementary to that reported by Sanchez-Saavedra et al. (1990MNRAS.246..458S), with 42 galaxies in the northern hemisphere, and to that by Reshetnikov & Combes (1999A&AS..138..101R), with 60 optical warps. The limits of the present catalog are: logr_25_>0.60, B_1_<14.5, DE(2000)<0{deg}, -2.5<t.7. Therefore, lenticular galaxies have also been considered. This catalog lists 150 warped galaxies out of a sample of 276 edge-on galaxies and covers the whole southern hemisphere, except the Avoidance Zone. It is therefore very suitable for statistical studies of warps. It also provides a source guide for detailed particular observations. We confirm the large frequency of warped spirals: nearly all galaxies are warped. The frequency and warp angle do not present important differences for the different types of spirals. However, no lenticular warped galaxy has been found within the specified limits. This finding constitutes an important restriction for theoretical models.
515. Warps of galaxies
- ID:
- ivo://CDS.VizieR/J/A+A/391/519
- Title:
- Warps of galaxies
- Short Name:
- J/A+A/391/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From a comparison of the different parameters of warped galaxies in the radio, and especially in the visible, we find that: a) No large galaxy (large mass or radius) has been found to have high amplitude in the warp, and there is no correlation of size/mass with the degree of asymmetry of the warp. b) The disc density and the ratio of dark to luminous mass show an opposing trend: smaller values give more asymmetric warps in the inner radii (optical warps) but show no correlation with the amplitude of the warp; however, in the external radii is there no correlation with asymmetry. c) A third anticorrelation appears in a comparison of the amplitude and degree of asymmetry in the warped galaxies. Hence, it seems that very massive dark matter haloes have nothing to do with the formation of warps but only with the degree of symmetry in the inner radii, and are unrelated to the warp shape for the outermost radii. Denser discs show the same dependence.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/927
- Title:
- Wide-field optical imaging of 4 fields
- Short Name:
- J/MNRAS/416/927
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present u-, g-, r-, i- and z-band optical images and associated catalogues taken primarily with the Isaac Newton Telescope Wide Field Camera on the European Large Area ISO Survey (ELAIS) N1 and N2, First Look Survey and Lockman Hole fields comprising a total of 1000h of integration time over 80deg^2^ and approximately 4.3 million objects. In this paper we outline the observations and data processing and characterize the completeness, reliability, photometric and astrometric accuracy of this data set. All images have been photometrically calibrated using the Sloan Digital Sky Survey and a uniform and homogeneous data set is composed over all the observed fields. Magnitude limits are u, g, r, i, z of 23.9, 24.5, 24.0, 23.3, 22.0 (AB, 5{sigma}). These data have been used for optical identification of past and ongoing projects including the surveys ELAIS, Spitzer Wide-Area Infrared Extragalactic Survey, Spitzer Extragalactic Representative Volume Survey and Herschel Multi-tiered Extragalactic Survey.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A104
- Title:
- WINGS cluster galaxies structural parameters
- Short Name:
- J/A+A/633/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength analysis of the galaxies in nine clusters selected from the WINGS dataset, examining how galaxy structure varies as a function of wavelength and environment using the state of the art software galapagos-2. We simultaneously fit single-Sersic functions on three optical (u, B and V) and two near-infrared (J and K) bands thus creating a wavelength-dependent model of each galaxy. We measure the magnitudes, effective radius (Re), the Sersic index (n), axis ratio, and position angle in each band. The sample contains 790 cluster members (located close to the cluster centre <0.64xR200) and 254 non-member galaxies that we further separate based on their morphology into ellipticals, lenticulars, and spirals. We find that the Sersic index of all galaxies inside clusters remains nearly constant with wavelength while Re decreases as wavelength increases for all morphological types. We do not observe a significant variation on n and Re as a function of projected local density and distance from the clusters centre. Comparing the n and Re of bright cluster galaxies with a subsample of non-member galaxies we find that bright cluster galaxies are more concentrated (display high n values) and are more compact (low Re). Moreover, the light profile (N) and size (R) of bright cluster galaxies does not change as a function of wavelength in the same manner as non-member galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/43
- Title:
- WWFI g'-band obs. of bright cluster galaxies
- Short Name:
- J/ApJS/247/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of 170 local (z<~0.08) galaxy clusters in the northern hemisphere have been obtained with the Wendelstein Telescope Wide Field Imager (WWFI). We correct for systematic effects such as point-spread function broadening, foreground star contamination, relative bias offsets, and charge persistence. Background inhomogeneities induced by scattered light are reduced down to {Delta}SB>31 g' mag/arcsec^2^ by large dithering and subtraction of night-sky flats. Residual background inhomogeneities brighter than SB_{sigma}_<27.6 g' mag/arcsec^2^ caused by galactic cirrus are detected in front of 23% of the clusters. However, the large field of view allows discrimination between accretion signatures and galactic cirrus. We detect accretion signatures in the form of tidal streams in 22%, shells in 9.4%, and multiple nuclei in 47% of the brightest cluster galaxies (BCGs) and find two BCGs in 7% of the clusters. We measure semimajor-axis surface brightness profiles of the BCGs and their surrounding intracluster light (ICL) down to a limiting surface brightness of SB=30 g' mag/arcsec^2^. The spatial resolution in the inner regions is increased by combining the WWFI light profiles with those that we measured from archival Hubble Space Telescope images or deconvolved WWFI images. We find that 71% of the BCG+ICL systems have surface brightness (SB) profiles that are well described by a single Sersic function, whereas 29% require a double Sersic function to obtain a good fit. We find that BCGs have scaling relations that differ markedly from those of normal ellipticals, likely due to their indistinguishable embedding in the ICL.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A5
- Title:
- X-ray absorption in INTEGRAL AGN
- Short Name:
- J/A+A/639/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work the INTEGRAL hard X-ray selected sample of AGN has been used to investigate the possible contribution of absorbing material distributed within the host galaxies to the total amount of NH measured in the X-ray band. We collected all the available axial ratio measurements of the galaxies hosting our AGN together with their morphological information and find that also for our hard X-ray selected sample a deficit of edge-on galaxies hosting type 1 AGN is present. We estimate that in our hard X-ray selected sample there is a deficit of 24% (+/-5%) of type 1 AGN. Possible bias in redshift has been excluded, as we found the same effect in a well determined range of z where the number and the distributions of the two classes are statistically the same. Our findings clearly indicate that material located in the host galaxy on scales of hundreds of parsecs and not aligned with the putative absorbing torus of the AGN can contribute to the total amount of column density. This galactic absorber can be large enough to hide the broad line region of some type 1 AGN causing their classification as type 2 objects and giving rise to the deficiency of type 1 in edge-on galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/810
- Title:
- X-ray emitters in the Groth-Westphal strip
- Short Name:
- J/ApJ/706/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Groth field is one of the sky regions that will be targeted by the OSIRIS Tunable Filter Emission Line Object survey in the optical 820nm and 920nm atmospheric windows. In the present paper, public Chandra X-ray data with total exposure time of 200ks are analyzed and combined with optical broadband data of the Groth field, in order to study a set of optical structural parameters of the X-ray emitters and its relation with X-ray properties. To this aim, we processed the raw, public X-ray data using the Chandra Interactive Analysis of Observations, and determined and analyzed different structural parameters, in order to produce a morphological classification of X-ray sources. We present the morphology of 340 X-ray emitters with optical counterpart detected. Objects have been classified by X-ray type using a diagnostic diagram relating X-ray-to-optical ratio (X/O) to hardness ratio. We did not find any clear correlation between X-ray and morphological types. We analyzed the angular clustering of X-ray sources with optical counterpart using two-point correlation functions. A significant positive angular clustering was obtained from a preliminary analysis of four subsamples of the X-ray sources catalog. The clustering signal of the optically extended counterparts is similar to that of strongly clustered populations like red and very red galaxies, suggesting that the environment plays an important role in active galactic nuclei phenomena. Finally, we combined optical structural parameters with other X-ray and optical properties, and we confirmed an anticorrelation between the X/O ratio and the Abraham concentration index, which might suggest that early-type galaxies have lower Eddington rates than those of late-type galaxies.