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- ID:
- ivo://CDS.VizieR/J/A+A/650/A146
- Title:
- Distant, pulsating red giants in southern halo
- Short Name:
- J/A+A/650/A146
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- To investigate the asymptotic giant branch (AGB) population in the Galactic halo, we search for pulsating AGB stars at a heliocentric distance over 50kpc. Our research is based on the Catalina Southern Survey (CSS) catalogue of variables, comprising 1286 long-period variables (LPVs) with declination less than -20{deg}. We first focus on the 77 stars in the cap abs(b)>30deg for which spectral M-type or C-type classification can be derived from Hamburg-ESO objective prism spectra. Most of these are oxygen-rich (M-type) and very few are carbon rich. The periods are in the range 100-500 days, and CSS amplitudes are up to 3mag. In this small sample, no halo AGB star is fainter than Ks0=12.5. This may be due to the scarcity of AGBs in the outer halo, or insufficient instrumental depth. Leaving aside spectral information, we then searched for even fainter pulsators (Ks>12.5) in the entire CSS catalogue. Gaia astrometry makes it possible to identify some contaminants. Our final result is the identification of ten candidate distant LPVs. If these ten stars obey the fundamental mode K-band period luminosity relation used for Miras and small-amplitude Miras, their distances are between 50 and 120kpc from the Sun. In a diagram showing distance versus Gaia tangential velocity, these ten stars have positions similar to those of other objects in the halo, such as globular clusters and dwarf galaxies. We also detect some underluminous AGBs that deserve further study. A detailed catalogue of the 77 high-latitude M or C stars will be made available at the CDS.
- ID:
- ivo://CDS.VizieR/J/MNRAS/394/2197
- Title:
- Distant radio galaxies in southern hemisphere
- Short Name:
- J/MNRAS/394/2197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of 234 ultra-steep-spectrum (USS) selected radio sources in order to find high-redshift radio galaxies. The sample covers the declination range -40{deg}<{delta}<-30{deg} in the overlap region between the 1400-MHz National Radio Astronomy Observatory (NRAO) Very Large Array (VLA) Sky Survey (NVSS), 408-MHz Revised Molonglo Reference Catalogue and the 843-MHz Sydney University Molonglo Sky Survey (the MRCR-SUMSS sample). This is the second in a series of papers on the MRCR-SUMSS sample, and here we present the K-band (2.2{mu}m) imaging of 173 of the sources primarily from the Magellan and the Anglo-Australian Telescopes. We detect a counterpart to the radio source in 93 per cent of the new K-band images which, along with previously published data, makes this the largest published sample of K-band counterparts to USS-selected radio galaxies. The location of the K-band identification has been compared to the features of the radio emission for the double sources. We find that the identification is most likely to lie near the mid-point of the radio lobes rather than closer to the brighter lobe, making the centroid a less likely place to find the optical counterpart. 79 per cent of the identifications are less than 1arcsec from the radio lobe axis. These results differ from studies of low-redshift radio samples where the environments are typically not nearly so dense and disturbed as those at high redshift. In contrast to some literature samples, we find that the majority of our sample shows no alignment between the near-infrared and radio axes. Several different morphologies of aligned structures are found and those that are aligned within 10{deg} are consistent with jet-induced star formation. The distribution and median value of the K-band magnitudes for the MRCR-SUMSS sample are found to be similar to several other USS-selected samples even though each sample has a very different median 1400MHz flux density. USS selection from a lower radio-frequency sample has not netted fainter K-band magnitudes, which may imply that the k-correction is not responsible for the effectiveness of USS selection.
- ID:
- ivo://CDS.VizieR/J/ApJ/855/43
- Title:
- Distant RR Lyrae stars discovered with HiTS
- Short Name:
- J/ApJ/855/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of distant RR Lyrae stars, including the most distant known in the Milky Way, using data taken in the g-band with the Dark Energy Camera as part of the High cadence Transient Survey (HiTS; 2014 campaign). We detect a total of 173 RR Lyrae stars over a ~120deg^2^ area, including both known RR Lyrae and new detections. The heliocentric distances dH of the full sample range from 9 to >200kpc, with 18 of them beyond 90kpc. We identify three sub-groups of RR Lyrae as members of known systems: the Sextans dwarf spheroidal galaxy, for which we report 46 new discoveries, and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology, we fit spherical and ellipsoidal profiles of the form {rho}(R)~Rn to the radial density distribution of RR Lyrae in the Galactic halo. The best fit corresponds to the spherical case, for which we obtain a simple power-law index of n=-4.17_-0.20_^+0.18^, consistent with recent studies made with samples covering shorter distances. The pulsational properties of the outermost RR Lyrae in the sample (dH>90kpc) differ from the ones in the halo population at closer distances. The distribution of the stars in a period-amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups, similar to what is found in the ultra-faint dwarf satellites around the Milky Way. The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/680/70
- Title:
- Distant spheroids in the GOODS fields
- Short Name:
- J/ApJ/680/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first results of a new study aimed at understanding the diversity and evolutionary history of distant galactic bulges in the context of now well-established trends for pure spheroidal galaxies. To this end, bulges have been isolated for a sample of 137 spiral galaxies within the redshift range 0.1<z<1.2 in the GOODS fields. Using proven photometric techniques, we determine the characteristic parameters (size, surface brightness, profile shape) of both the disk and bulge components in our sample. In agreement with earlier work that utilized aperture colors, distant bulges show a broader range of optical colors than would be the case for passively evolving populations. To quantify the amount of recent star formation necessary to explain this result, we used DEIMOS to secure stellar velocity dispersions for a sizeable fraction of our sample. This has enabled us to compare the fundamental plane of our distant bulges with that for spheroidal galaxies in a similar redshift range.
- ID:
- ivo://CDS.VizieR/J/AJ/123/51
- Title:
- Distribution of Abell and APM clusters
- Short Name:
- J/AJ/123/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of how well the large-scale structure of the universe is traced by clusters from the Abell catalog and from the Automated Plate Measuring Facility (APM). We investigate selection functions for both cluster catalogs, using samples of all clusters (including clusters with estimated redshifts) and samples of clusters with measured redshifts. We present a catalog of superclusters of galaxies, based on APM clusters up to a redshift z_lim_=0.13.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1509
- Title:
- Distribution of AGNs in galaxy clusters
- Short Name:
- J/MNRAS/392/1509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the X-ray point source populations in 182 Chandra images of galaxy clusters at z>0.1 with exposure time >10ks, as well as 44 non-cluster fields. The analysis of the number and flux of these sources, using a detailed pipeline to predict the distribution of non-cluster sources in each field, reveals an excess of X-ray point sources associated with the galaxy clusters. A sample of 148 galaxy clusters at 0.1<z<0.9 , with no other nearby clusters, shows an excess of 230 cluster sources in total, an average of ~1.5 sources per cluster. The lack of optical data for these clusters limits the physical interpretation of this result, as we cannot calculate the fraction of cluster galaxies hosting X-ray sources. However, the fluxes of the excess sources indicate that over half of them are very likely to be active galactic nuclei (AGN), and the radial distribution shows that they are quite evenly distributed over the central 1Mpc of the cluster, with almost no sources found beyond this radius. We also use this pipeline to successfully reproduce the results of previous studies, particularly the higher density of sources in the central 0.5Mpc of a few cluster fields, but show that these conclusions are not generally valid for this larger sample of clusters. We conclude that some of these differences may be due to the sample properties, such as the size and redshift of the clusters studied, or a lack of publications for cluster fields with no excess sources. This paper also presents the basic X-ray properties of the galaxy clusters, and in subsequent papers in this series the dependence of the AGN population on these cluster properties will be evaluated.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/L31
- Title:
- Distribution of ^26^Al in the solar system
- Short Name:
- J/ApJ/733/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is believed that ^26^Al, a short-lived (t_1/2_=0.73Ma) and now extinct radionuclide, was uniformly distributed in the nascent solar system (SS) with the initial ^26^Al/^27^Al ratio of ~5.2x10^-5^, suggesting an external, stellar origin rather than local, solar source. However, the stellar source of ^26^Al and the manner in which it was injected into the SS remain controversial: the ^26^Al could have been produced by an asymptotic giant branch star, a supernova, or a Wolf-Rayet star and injected either into the protosolar molecular cloud, protosolar cloud core, or protoplanetary disk. Corundum (Al_2_O_3_) is predicted to be the first condensate from a cooling gas of solar composition. Here we show that micron-sized corundum condensates from ^16^O-rich ({Delta}^17^O~-25%) gas of solar composition recorded heterogeneous distribution of ^26^Al at the birth of the SS: the inferred initial ^26^Al/^27^Al ratio ranges from ~6.5x10^-5^ to <2x10^-6^; 52% of corundum grains measured are ^26^Al-poor. Abundant ^26^Al-poor, ^16^O-rich refractory objects include grossite- and hibonite-rich calcium-aluminum-rich inclusions (CAIs) in CH (high metal abundance and high iron concentration) chondrites, platy hibonite crystals in CM (Mighei-like) chondrites, and CAIs with fractionation and unidentified nuclear effects CAIs chondrites. Considering the apparently early and short duration (<0.3Ma) of condensation of refractory ^16^O-rich solids in the SS, we infer that ^26^Al was injected into the collapsing protosolar molecular cloud and later homogenized in the protoplanetary disk. The apparent lack of correlation between ^26^Al abundance and O-isotope composition of corundum grains constrains the stellar source of ^26^Al in the SS.
- ID:
- ivo://CDS.VizieR/J/ApJS/94/127
- Title:
- Distribution of H I in the ISM. I.
- Short Name:
- J/ApJS/94/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compile, from the existing literature, the largest sample to date (842 data points) of hydrogen column density measurements, N(HI), of the gas in the interstellar medium. We include only results obtained from absorption measurements toward individual stars (594 in our sample) in an effort to construct a three-dimensional picture of the interstellar gas. We derive hydrogen column densities toward a fraction of the stars in the sample from published column density measurements of metal ions. A three-dimensional physical model derived from this data set will be presented in a companion paper. The observed stars span distances from a few parsecs to a few thousand parsecs, and more than half of the sample serves to describe the local interstellar medium within a few hundred parsecs of the Sun. Hydrogen column densities range from 10^17^ to 10^22^cm^-2^. We describe here the various observational methods used to estimate the hydrogen column densities and present the table with the stellar and hydrogen column density data. The provided table is intended as a global reference work, not to introduce new results.
- ID:
- ivo://CDS.VizieR/J/ApJS/178/1
- Title:
- Distribution of HII regions in disk galaxies
- Short Name:
- J/ApJS/178/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is known that interstellar gas has a fractal structure in a wide range of spatial scales with a fractal dimension that seems to be a constant around D_f_~2.7. It is expected that stars forming from this fractal medium exhibit similar fractal patterns. Here we address this issue by quantifying the degree to which star-forming events are clumped. We develop, test, and apply a precise and accurate technique to calculate the correlation dimension Dc of the distribution of HII regions in a sample of disk galaxies.