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421. A deep multicolor survey. I.
ID:
ivo://CDS.VizieR/J/ApJS/104/185
Title:
A deep multicolor survey. I.
Short Name:
J/ApJS/104/185
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Kitt Peak National Observatory 4m Mayall telescope to image 0.83 square degrees of sky in six fields at high Galactic latitude in six filters spanning 3000-10000A to magnitude limits ranging from 22.1 to 23.8. We have assembled a catalog of 21375 stellar objects detected in the fields for use primilary in conducting a multicolor search for quasars. This paper describes the data reduction techniques used on the CCD data, the methods used to construct the stellar object catalog, and the simulations performed to understand its completeness and contamination.
422. A deep multicolor survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/462/614
Title:
A deep multicolor survey. II.
Short Name:
J/ApJ/462/614
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Kitt Peak National Observatory 4m Mayall telescope to image 0.83 square degrees of sky in six fields at high galactic latitude in six filters spanning 3000-10000A to magnitude limits ranging from 22.1 to 23.8. As a first use of this database, we have conducted a multicolor survey for quasars. We discuss various methods of selecting outliers in different color-color diagrams and multicolor space that have been used to identify quasars at all redshifts from their colors alone. We discuss the initial results of our program of spectroscopic identification which has so far resulted in the identification of over 40 faint quasars, including one a z>4, a similar number of compact narrow emission-line galaxies, and a number of unusual and potentially interesting stars. We use these spectroscopic results, along with extensive simulations of quasar spectra, to study the efficiency of our candidate selection procedures. Finally, we compare the number counts of our quasars and quasar candidates to the expected numbers based on previous studies of the quasar luminosity function. The agreement of our observations with these expectations is good in most cases. However, we do estimate that our survey contains more quasars with B<21 and z<2.3 than expected from the results published by Koo & Kron in (1988ApJ...325...92K) and more z>3 quasars than expected from the results published by Warren, Hewett & Osmer in (1994ApJ...421..412W), both at the 3 {sigma} level. Additional spectroscopic observations will be required to confirm or refute these excesses.
423. A deep multicolor survey. III.
ID:
ivo://CDS.VizieR/J/AJ/114/2269
Title:
A deep multicolor survey. III.
Short Name:
J/AJ/114/2269
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have made spectroscopic identifications of 39 additional quasar candidates from the Deep Multicolor Survey (DMS) of Hall et al. (1996, Cat. <J/ApJ/462/614>). We have identified 9 new quasars with 0.3<z<2.8 and 16.8<B<21.6, all from the group of candidates with ultraviolet excess (UVX). No new quasars with z>3 were found among the observed candidates selected due to their red (B-R) and (V-R) colors. As a result, there are now 55 confirmed quasars in the survey: 42 with 0.3<z<2, nine with 2<z<3, three with 3<z<4, and 1 at z=4.3. One new quasar, DMS 0059-0055, is very bright with B=16.8 and z=0.3, making its detection by our survey very unexpected. Including this new spectroscopy, the results of the DMS are converging with the predicted space densities of other surveys. In particular, we no longer find an excess of quasars with z<2.3 and B<21 in the survey over predictions based on models by Koo & Kron (1988ApJ...325...92K). Also, the excess in the number of quasars seen at z>3 over predictions based on models by Warren et al. (1994ApJ...421..412W) is less than previously suggested. We also demonstrate the success of our quasar color modeling which is important in assessing the completeness of our survey.
424. A deep radio survey of Abell 2125. I
ID:
ivo://CDS.VizieR/J/AJ/129/26
Title:
A deep radio survey of Abell 2125. I
Short Name:
J/AJ/129/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a description of deep radio, optical, and near-IR observations taken with the VLA, the KPNO 2m telescope, and the KPNO 4m telescope of the region containing the rich cluster of galaxies Abell 2125. The reduction of each data set is described. A catalog of radio sources apparently not associated with members of A2125 and the associated R-band magnitudes is presented.
425. A deep radio survey of Abell 2125. II
ID:
ivo://CDS.VizieR/J/AJ/129/31
Title:
A deep radio survey of Abell 2125. II
Short Name:
J/AJ/129/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using our extensive radio, optical, near-IR, and X-ray imaging and spectroscopy, we consider the reason for the unusually large number of radio-detected galaxies, mostly found outside the cluster core, in Abell 2125 (z=0.2465, richness class 4). With 20cm VLA data, we detect continuum emission from 90 cluster members. The multiwavelength properties of these galaxies suggest that most of the radio emission is due to an enhanced star formation rate. The recent dynamical study of Miller et al. (2004, Cat. <J/ApJ/613/841>) suggests that A2125 is undergoing a major cluster-cluster merger, with our view within 30{deg} of the merger axis and within 0.2Gyr of core passage. The combination of projection effects and the physical processes at work during this special time in the cluster's evolution seem likely to be responsible for the unusual level of activity we see in the cluster. We argue that tidal effects on individual cluster members, often far from the cluster core, are responsible for the increased star formation. Our results are consistent with the idea that disk galaxies during this phase of a cluster's evolution undergo rapid evolution through a burst of star formation on their way to becoming S0 galaxies.
426. A deep survey of galaxies
ID:
ivo://CDS.VizieR/J/AJ/88/1285
Title:
A deep survey of galaxies
Short Name:
J/AJ/88/1285
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of galaxies in six fields, each of area 2 sq deg, located in the North and South galactic polar caps. Photoelectrically calibrated photographic magnitudes and J-F colors have been determined for 512 galaxies brighter than completeness limits which range from F=16.5 to F=17.2 among the fields. Velocities, with typical accuracies of 150km/s have been obtained for 280 of the brighter galaxies. Using these data and previously published work, we determine the general galaxy luminosity function parameters to be M*_F_=-22.7, {alpha}=-1.25, and the mean visual luminosity density of the universe to be {rho}=2.3x10^8^hL_{sun}_/Mpc^3^. Assuming M/L_v_=300h, this implies {OMEGA}~0.26.
427. A diagnostic diagram for Seyfert 2 Galaxies
ID:
ivo://CDS.VizieR/J/ApJS/121/473
Title:
A diagnostic diagram for Seyfert 2 Galaxies
Short Name:
J/ApJS/121/473
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present and discuss a three-dimensional diagnostic diagram for Seyfert 2 galaxies obtained using X-ray and [O III] data on a large sample of objects (reported in the Appendix). The diagram shows the K{alpha} iron line equivalent width as a function of both the column density derived from the photoelectric cutoff and the 2-10 keV flux normalized to the [O III] optical-line flux (the latter corrected for extinction and assumed to be a true indicator of the source intrinsic luminosity). We find that the hard X-ray properties of type 2 objects depend on a single parameter, the absorbing column density along the line of sight, in accordance with the unified model. The diagram can be used to identify Compton-thick sources and to isolate and study peculiar objects. From this analysis we have obtained a column density distribution of Seyfert 2 galaxies that is thought to be a good approximation of the real distribution. A large population of heavily absorbed objects is discovered, including many Compton-thick candidates. Our results indicate that the mean log N_H_cm^-2^ in type 2 Seyfert galaxies is 23.5 and that as many as 23%-30% of sources have N_H_=>10^24^cm^-2^.
428. AD Leo high resolution spectra
ID:
ivo://CDS.VizieR/J/A+A/637/A13
Title:
AD Leo high resolution spectra
Short Name:
J/A+A/637/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance <0.4AU. Detections of CMEs on these stars have been sparse, and previous studies have therefore modelled their occurrence frequency by scaling up solar relations. However, because the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. We used a large number of high-resolution spectra to study flares, CMEs, and their dynamics of the active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. We obtained more than 2000 high-resolution spectra (R~35000) of the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these data, we studied the behaviour of the spectral lines H{alpha}, H{beta}, and HeI 5876 in detail and investigated asymmetric features that might be Doppler signatures of CMEs. We detected numerous flares. The largest flare emitted 8.32x10^31^erg in H{beta} and 2.12x10^32^erg in H{alpha}. Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare-to-CME relation for M dwarfs as for the Sun.
429. Advanced Camera for Surveys
ID:
ivo://archive.stsci.edu/hst/acs
Title:
Advanced Camera for Surveys
Short Name:
HST.ACS
Date:
23 Jul 2020 19:47:47
Publisher:
Space Telescope Science Institute Archive
Description:
HST Advanced Camera for Surveys (ACS) - Images: CCD images between 3,700 - 11
430. A 3D view of the Hyades population
ID:
ivo://CDS.VizieR/J/A+A/623/A35
Title:
A 3D view of the Hyades population
Short Name:
J/A+A/623/A35
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our scientific goal is to provide a 3D map of the nearest open cluster to the Sun, the Hyades, combining the recent release of Gaia astrometric data, ground-based parallaxes of sub-stellar member candidates and photometric data from surveys which cover large areas of the cluster. We combined the second Gaia release with ground-based H-band parallaxes obtained with the infrared camera on the 2-m robotic Liverpool telescope to astrometrically identify stellar and sub-stellar members of the Hyades, the nearest open cluster to the Sun. We find 1764 objects within 70 degree radius from the cluster center from the Gaia second data release, whose kinematic properties are consistent with the Hyades. We limit our study to 30pc from the cluster center (47.03+/-0.20pc) where we identify 710 candidate members, including 85 and 385 in the core and tidal radius, respectively. We determine proper motions and parallaxes of eight candidate brown dwarf members and confirm their membership. Using the 3D positions and a model-based mass-luminosity relation we derive a luminosity and mass function in the 0.04 to 2.5M_{sun}_ range. We confirm evidence for mass segregation in the Hyades and find a dearth of brown dwarfs in the core of the cluster. From the white dwarf members we estimate an age of 640^+67^_-49_Myr. We identify a list of members in the Hyades cluster from the most massive stars down to the brown dwarfs. We produce for the first time a 3D map of the Hyades cluster in the stellar and sub-stellar regimes and make available the list of candidate members.

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