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3101. ugriz colors of RR Lyrae stars in SDSS Stripe 82
ID:
ivo://CDS.VizieR/J/ApJ/834/160
Title:
ugriz colors of RR Lyrae stars in SDSS Stripe 82
Short Name:
J/ApJ/834/160
Date:
21 Oct 2021
Publisher:
CDS
Description:
Investigation of period-color (PC) and amplitude-color (AC) relations at the maximum and minimum light can be used to probe the interaction of the hydrogen ionization front (HIF) with the photosphere and the radiation hydrodynamics of the outer envelopes of Cepheids and RR Lyraes. For example, theoretical calculations indicated that such interactions would occur at minimum light for RR Lyrae and result in a flatter PC relation. In the past, the PC and AC relations have been investigated by using either the (V-R)_MACHO_ or (V-I) colors. In this work, we extend previous work to other bands by analyzing the RR Lyraes in the Sloan Digital Sky Survey Stripe 82 Region. Multi-epoch data are available for RR Lyraes located within the footprint of the Stripe 82 Region in five (ugriz) bands. We present the PC and AC relations at maximum and minimum light in four colors: (u-g)_0_, (g-r)_0_, (r-i)_0_, and (i-z)_0_, after they are corrected for extinction. We found that the PC and AC relations for this sample of RR Lyraes show a complex nature in the form of flat, linear or quadratic relations. Furthermore, the PC relations at minimum light for fundamental mode RR Lyrae stars are separated according to the Oosterhoff type, especially in the (g-r)_0_ and (r-i)_0_ colors. If only considering the results from linear regressions, our results are quantitatively consistent with the theory of HIF-photosphere interaction for both fundamental and first overtone RR Lyraes.
3102. u'g'r'i'z' photometry in NGC 188
ID:
ivo://CDS.VizieR/J/AJ/133/1409
Title:
u'g'r'i'z' photometry in NGC 188
Short Name:
J/AJ/133/1409
Date:
21 Oct 2021
Publisher:
CDS
Description:
We continue our series of papers describing the results of a photometric survey of open star clusters, primarily in the southern hemisphere, taken in the u'g'r'i'z' filter system. The entire observed sample covered more than 100 clusters, but here we present data only on NGC 188, which is one of the oldest open clusters known in the Milky Way. We fit the Padova theoretical isochrones to our data. Assuming a solar metallicity for NGC 188, we find a distance of 1700+/-100pc, an age of 7.5+/-0.7Gyr, and a reddening E(B-V) of 0.025+/-0.005. This yields a distance modulus of 11.23+/-0.14.
3103. u'g'r'i'z' photometry in NGC 2548 (M48)
ID:
ivo://CDS.VizieR/J/AJ/127/2210
Title:
u'g'r'i'z' photometry in NGC 2548 (M48)
Short Name:
J/AJ/127/2210
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present initial results of a photometric survey of open star clusters, primarily in the southern hemisphere, taken in the u'g'r'i'z' filter system. While our entire observed sample covers more than 100 clusters, here we present data for NGC 2548 (M48), which is a cluster characterized in the UBV and DDO photometric systems. We compare our results to the published values from other observers and to the Padova theoretical isochrones and metallicity curves. These observations demonstrate that the u'g'r'i'z' filters can play an important role in determining the metallicity of stars and clusters. We begin this series of papers with a study of NGC 2548 because we have obtained data on this cluster not only with our main program telescope, the CTIO Curtis Schmidt, but also with the US Naval Observatory (USNO) 1.0m telescope (the telescope used to define the u'g'r'i'z' system), and with the Sloan Digital Sky Survey (SDSS) 0.5m Photometric Telescope (the photometric monitoring telescope used to calibrate the SDSS 2.5m telescope imaging data). We have used the data from this study to validate our ability to transform measurements obtained on other telescopes to the standard USNO 1.0m u'g'r'i'z' system. This validation is particularly important for very red stars, for which the original u'g'r'i'z' standard star network is poorly constrained.
3104. u*g*r*i*z* Photometry of stars, galaxies, QSOs
ID:
ivo://CDS.VizieR/J/ApJS/123/377
Title:
u*g*r*i*z* Photometry of stars, galaxies, QSOs
Short Name:
J/ApJS/123/377
Date:
21 Oct 2021
Publisher:
CDS
Description:
The catalog (table 5 of the paper) contains the measurements of 2262 sources, including 334 extended sources, 1915 point sources, and 13 known QSOs, in five passbands close to the u'g'r'i'z' passbands of SDSS (see the definition of the photometric system in Richards et al., 1997PASP..109...39R). Of these objects, over 1600 are measured in 15 fields covering 0.5deg^2^, with a limiting magnitude of r*<19.5, similar to the photometric limit of the SDSS spectroscopic survey.
3105. UGR photometry of LBG candidates at z~3
ID:
ivo://CDS.VizieR/J/A+A/563/A142
Title:
UGR photometry of LBG candidates at z~3
Short Name:
J/A+A/563/A142
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a deep multi wavelength imaging survey (UGR) in 3 different fields, Q0933, Q1623 and COSMOS, for a total area of ~1500arcmin^2^ The data were obtained with the Large Binocular Camera on the Large Binocular Telescope. To select our LBG candidates we adopt the well established and widely used color selection criterion (U-G vs. G-R). One of the main advantages of our survey is that it has a wider dynamic color range for U drop-out selection compared to previous studies. This allows us to fully exploit the depth of our R band images, obtaining a robust sample with few interlopers. In addition, for 2 of our fields we have spectroscopic redshift information that is necessary to better estimate the completeness of our sample and interloper fraction. Our limiting magnitudes reach 27.0(AB) in the R band (5{sigma}) and 28.6(AB) in the U band (1{sigma}). This dataset was used to derive Lyman Break Galaxy candidates at z~3. We obtained a catalog with a total of 12264 sources down to the 50% completeness magnitude limit in the R band for each field. We find a surface density of ~3 LBG candidates arcmin^-2^ down to R=25.5, where completeness is >=95% for all 3 fields. This number is higher than the original studies, but consistent with more recent samples.
3106. UGSs. V. kernel approach
ID:
ivo://CDS.VizieR/J/ApJS/209/10
Title:
UGSs. V. kernel approach
Short Name:
J/ApJS/209/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
Nearly one-third of the {gamma}-ray sources detected by Fermi are still unidentified, despite significant recent progress in this area. However, all of the {gamma}-ray extragalactic sources associated in the second Fermi-LAT catalog have a radio counterpart. Motivated by this observational evidence, we investigate all the radio sources of the major radio surveys that lie within the positional uncertainty region of the unidentified {gamma}-ray sources (UGSs) at a 95% level of confidence. First, we search for their infrared counterparts in the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) and then we analyze their IR colors in comparison with those of the known {gamma}-ray blazars. We propose a new approach, on the basis of a two-dimensional kernel density estimation technique in the single [3.4]-[4.6]-[12]{mu}m WISE color-color plot, replacing the constraint imposed in our previous investigations on the detection at 22{mu}m of each potential IR counterpart of the UGSs with associated radio emission. The main goal of this analysis is to find distant {gamma}-ray blazar candidates that, being too faint at 22{mu}m, are not detected by WISE and thus are not selected by our purely IR-based methods. We find 55 UGSs that likely correspond to radio sources with blazar-like IR signatures. An additional 11 UGSs that have blazar-like IR colors have been found within the sample of sources found with deep recent Australia Telescope Compact Array observations.
3107. UKIDSS+FIRST+SDSS red QSOs candidates
ID:
ivo://CDS.VizieR/J/ApJ/778/127
Title:
UKIDSS+FIRST+SDSS red QSOs candidates
Short Name:
J/ApJ/778/127
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K<=17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190deg^2^. These candidates reach up to ~1.5mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B-V)>0.1, including 3 at z>2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z>~2) are only moderately reddened, with E(B-V)~0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B-V)>~0.5) at z>2 and a depth of K=17, we would need to survey at least ~2.5 times more area.
3108. UKS 2 open cluster BV photometry
ID:
ivo://CDS.VizieR/J/A+AS/145/399
Title:
UKS 2 open cluster BV photometry
Short Name:
J/A+AS/145/399
Date:
21 Oct 2021
Publisher:
CDS
Description:
Colour-magnitude diagrams are presented for the first time, of the faint southern star cluster UKS 2, which was for a long time reported as a globular cluster candidate. The V vs. B-V diagrams indicate that UKS 2 is an open cluster with age comparable to that of the Hyades. It has a reddening of E(B-V)=0.40 and is located at a distance from the Sun of d_{sun}_=~7kpc. The cluster is located outside the solar radius at galactocentric distance projected on the plane r_GC_=~11kpc, and a height z=~-370pc.
3109. Ultra compact dwarfs and globulars in Hya I
ID:
ivo://CDS.VizieR/J/A+A/531/A4
Title:
Ultra compact dwarfs and globulars in Hya I
Short Name:
J/A+A/531/A4
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a large spectroscopic survey of compact, unresolved objects in the core of the Hydra I galaxy cluster (Abell 1060), with the aim of identifying ultra-compact dwarf galaxies (UCDs) and investigating the properties of the globular cluster (GC) system around the central cD galaxy NGC 3311. We obtained VIMOS medium-resolution spectra of about 1200 candidate objects with apparent magnitudes 18.5<V<24.0mag, covering both the bright end of the GC luminosity function and the luminosity range of all known UCDs.
3110. Ultra-cool dwarfs candidates in Gaia DR2
ID:
ivo://CDS.VizieR/J/A+A/619/L8
Title:
Ultra-cool dwarfs candidates in Gaia DR2
Short Name:
J/A+A/619/L8
Date:
21 Oct 2021
Publisher:
CDS
Description:
The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources. The resulting Hertzsprung-Russel diagram reveals fine structures throughout the mass range. This paper aims to investigate the content of Gaia DR2 at the low-mass end and to characterize ultra-cool and brown dwarfs. We first retrieved the sample of spectroscopically confirmed ultra-cool and brown dwarfs in Gaia DR2.We used their locus in the precise Hertzsprung-Russel diagram to select new candidates and to investigate their properties. The number of spectroscopically confirmed objects recovered in Gaia DR2 corresponds to 61% and 74% of the expected number of objects with an estimated Gaia magnitude G_est_<=21.5 and 20.3, respectively. This fills much of the gap to Gaia DR1. Furthermore, Gaia DR2 contains ~13000>=M7 and 631 new L candidates. A tentative classification suggests that a few hundred of them are young or subdwarf candidates. Their distance distribution shows that the solar neighborhood census is still incomplete. Conclusions. Gaia DR2 offers a great wealth of information on low-mass objects. It provides a homogeneous and precise catalog of candidates that is worthwhile to be further characterized with spectroscopic observations.