- ID:
- ivo://CDS.VizieR/J/A+A/639/A26
- Title:
- Cold HI, H2 and total H column density FITS maps
- Short Name:
- J/A+A/639/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There are significant amounts of H_2_ in the Milky Way. Due to its symmetry H_2_ does not radiate at radio frequencies. CO is thought to be a tracer for H_2_, however CO is formed at significantly higher opacities than H_2_. Thus, toward high Galactic latitudes significant amounts of H_2_ are hidden and called CO-dark. We demonstrate that the dust-to-gas ratio is a tool to identify locations and column densities of CO-dark H_2_. We adopt the hypothesis of a constant E(B-V)/NH ratio, independent of phase transitions from HI to H_2_. We investigate the Doppler temperatures T_D_, from a Gaussian decomposition of HI4PI data, to study temperature dependencies of E(B-V)/NHI. The E(B-V)/NHI ratio in the cold HI gas phase is high in comparison to the warmer one. We consider this as evidence that cold HI gas toward high Galactic latitudes is associated with H_2_. Beyond CO-bright regions we find for T_D_<1165K a correlation (NHI+2NH_2_)/NHI{prop.to}-log T_D_. In combination with a factor XCO=4.0x10^20^cm^-2^(K.km/s)^-1^ this yields for the full-sky NH/E(B-V)~5.1 to 6.7 10^21^cm^-2^mag^-1^, compatible with X-ray scattering and UV absorption line observations. Cold HI with T_D_<1165K contains on average 46% CO-dark H_2_. Prominent filaments have T_D_<220K and typical excitation temperatures Tex~50K. With a molecular gas fraction of >61% they are dominated dynamically by H_2_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/697/207
- Title:
- Cold stellar stream orbit fit
- Short Name:
- J/ApJ/697/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use velocity and metallicity information from Sloan Digital Sky Survey and Sloan Extension for Galactic Understanding and Exploration stellar spectroscopy to fit an orbit to the narrow 63{deg} stellar stream of Grillmair and Dionatos (GD; 2006ApJ...643L..17G). The stars in the stream have a retrograde orbit with eccentricity e=0.33 (perigalacticon of 14.4kpc and apogalacticon of 28.7kpc) and inclination approximately i~35{deg}. In the region of the orbit which is detected, it has a distance of about 7-11kpc from the Sun. Assuming a standard disk plus bulge and logarithmic halo potential for the Milky Way stars plus dark matter, the stream stars are moving with a large space velocity of approximately 276km/s at perigalacticon. Using this stream alone, we are unable to determine if the dark matter halo is oblate or prolate. The metallicity of the stream is [Fe/H]=-2.1+/-0.1. Observed proper motions for individual stream members above the main sequence turnoff are consistent with the derived orbit. None of the known globular clusters in the Milky Way have positions, radial velocities, and metallicities that are consistent with being the progenitor of the GD-1 stream.
- ID:
- ivo://CDS.VizieR/J/A+A/423/755
- Title:
- Color-Induced Displacement double stars in SDSS
- Short Name:
- J/A+A/423/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first successful application of the astrometric color-induced displacement technique (CID, the displacement of the photocenter between different band-passes dur to a varying contribution of differently colored components to the total light), originally proposed by Wielen (1996A&A...314..679W) for discovering unresolved binary stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/368
- Title:
- Color-magnitude relations of galaxies in CDFs
- Short Name:
- J/ApJ/720/368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend color-magnitude relations for moderate-luminosity X-ray active galactic nucleus (AGN) hosts and non-AGN galaxies through the galaxy formation epoch (z~1-4) in the Chandra Deep Field-North and Chandra Deep Field-South (CDF-N and CDF-S, respectively; jointly CDFs) surveys. This study was enabled by the deepest available X-ray data from the 2Ms CDF surveys as well as complementary ultradeep multiwavelength data in these regions. We utilized analyses of color-magnitude diagrams (CMDs) to assess the role of moderate-luminosity AGNs in galaxy evolution.
- ID:
- ivo://CDS.VizieR/J/ApJS/243/12
- Title:
- Colors of the Outer Solar System Origins Survey
- Short Name:
- J/ApJS/243/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Colours of the Outer Solar System Origins Survey is acquiring near-simultaneous g, r, and J photometry of unprecedented precision with the Gemini North Telescope, targeting nearly 100 trans-Neptunian objects (TNOs) brighter than m_r_=23.6mag discovered in the Outer Solar System Origins Survey. Combining the optical and near-infrared photometry with the well-characterized detection efficiency of the Colours of the Outer Solar System Origins Survey target sample will provide the first flux-limited compositional dynamical map of the outer solar system. In this paper, we describe our observing strategy and detail the data reduction processes we employ, including techniques to mitigate the impact of rotational variability. We present optical and near-infrared colors for 35 TNOs. We find two taxonomic groups for the dynamically excited TNOs, the neutral and red classes, which divide at g-r~0.75. Based on simple albedo and orbital distribution assumptions, we find that the neutral class outnumbers the red class, with a ratio of 4:1 and potentially as high as 11:1. Including in our analysis constraints from the cold classical objects, which are known to exhibit unique albedos and r-z colors, we find that within our measurement uncertainty our observations are consistent with the primordial solar system protoplanetesimal disk being neutral class dominated, with two major compositional divisions in grJ color space.
- ID:
- ivo://CDS.VizieR/J/AJ/157/94
- Title:
- Col-OSSOS: Properties of outer solar system objects
- Short Name:
- J/AJ/157/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Both physical and dynamical properties must be considered to constrain the origins of the dynamically excited distant solar system populations. We present high-precision (g-r) colors for 25 small (H_r_>5) dynamically excited trans-Neptunian objects (TNOs) and centaurs acquired as part of the Colours of the Outer Solar System Origins Survey. We combine our data set with previously published measurements and consider a set of 229 colors of outer solar system objects on dynamically excited orbits. The overall color distribution is bimodal and can be decomposed into two distinct classes, termed gray and red, that each has a normal color distribution. The two color classes have different inclination distributions: red objects have lower inclinations than the gray ones. This trend holds for all dynamically excited TNO populations. Even in the worst-case scenario, biases in the discovery surveys cannot account for this trend; it is intrinsic to the TNO population. Considering that TNOs are the precursors of centaurs, and that their inclinations are roughly preserved as they become centaurs, our finding solves the conundrum of centaurs being the only outer solar system population identified so far to exhibit this property. The different orbital distributions of the gray and red dynamically excited TNOs provide strong evidence that their colors are due to different formation locations in a disk of planetesimals with a compositional gradient.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/369
- Title:
- Colour and spectral index from the SLUGGS survey
- Short Name:
- J/MNRAS/446/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ~90 {AA}^-1^. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the H{alpha} and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.
- ID:
- ivo://CDS.VizieR/J/ApJ/600/L99
- Title:
- Colours of z~6 galaxies in GOODS
- Short Name:
- J/ApJ/600/L99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report early results on galaxies at z~6 selected from Hubble Space Telescope imaging for the Great Observatories Origins Deep Survey. Spectroscopy of one object with the Advanced Camera for Surveys grism and from the Keck and Very Large Telescope observatories shows a strong continuum break and asymmetric line emission, identified as Ly{alpha} at z=5.83. We find only five spatially extended candidates with signal-to-noise ratios greater than 10, two of which have spectroscopic confirmation. This is much fewer than would be expected if galaxies at z=6 had the same luminosity function as those at z=3. There are many fainter candidates, but we expect substantial contamination from foreground interlopers and spurious detections. Our best estimates favor a z=6 galaxy population with fainter luminosities, higher space density, and similar comoving ultraviolet emissivity to that at z=3, but this depends critically on counts at fluxes fainter than those reliably probed by the current data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/819
- Title:
- Combined NVSS-FIRST Galaxies (CoNFIG) sample
- Short Name:
- J/MNRAS/390/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoNFIG (Combined NVSS-FIRST Galaxies) sample is a new sample of 274 bright radio sources at 1.4GHz. It was defined by selecting all sources with S1.4GHz-1.3Jy from the NRAO Very Large Array (VLA) Sky Survey (NVSS) in the north field of the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey. New radio observations obtained with the VLA for 31 of the sources are presented. The sample has complete Fanaroff-Riley (FRI)/FRII morphology identification; optical identifications and redshifts are available for 80 and 89 per cent of the sample, respectively, yielding a mean redshift of ~0.71. One of the goals of this survey is to get better definitions of luminosity distributions and source counts of FRI/FRII sources separately, in order to determine the evolution of the luminosity function for each type of source. We present a preliminary analysis, showing that these data are an important step towards examining various evolutionary schemes for these objects and to confirm or correct the dual population unified scheme for radio active galactic nuclei (AGN). Improving our understanding of radio galaxy evolution will give better insight into the role of AGN feedback in galaxy formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1719
- Title:
- Combined NVSS-FIRST galaxies (CoNFIG) sample II
- Short Name:
- J/MNRAS/404/1719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper focuses on a comparison of the space densities of Fanaroff-Riley type I (FR I) and FR II sources at different epochs, with a particular focus on FR I sources. First, we present the concluding steps in constructing the Combined NVSS-FIRST Galaxies (CoNFIG) catalogue, including new Very Large Array observations, optical identifications and redshift estimates. The final catalogue consists of 859 sources over four samples (CoNFIG-1, -2, -3 and -4 with flux density limits of S1.4GHz=1.3, 0.8, 0.2 and 0.05Jy, respectively). It is 95.7 per cent complete in radio morphology classification and 74.3 per cent of the sources have redshift data. Combining CoNFIG with complementary samples, the distribution and evolution of FR I and FR II sources are investigated. We find that FR I sources undergo mild evolution and that, at the same radio luminosity, FR I and FR II sources show similar space density enhancements in various redshift ranges, possibly implying a common evolution.
