- 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.
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Search Results
- 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.
- 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.
- 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.
- 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^.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/145
- Title:
- A 3D Voronoi+Gapper galaxy cluster finder. II.
- Short Name:
- J/ApJ/869/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 1901 galaxy clusters (N_g_>=2) with the gapping-filtering in radial velocity (VoML+G) algorithm (Paper I; Campusano+ 2017ApJ...838..109P) on the two-Degree Field Galaxy Redshift Survey (2dFGRS). We present the 341 clusters with at least 10 galaxies that are within 0.009<z<0.14 (the Catalog), of which 254 (~75%) have counterparts in the literature (NED), with the remainder (87) plausibly "new" because of incompleteness of previous searches or unusual galaxy contents. The 207 clusters within z=0.04--0.09 are used to study the properties of the galaxy systems in the nearby universe, including their galaxy contents parameterized by the late-type galaxy fractions (f_L_). For this nearly complete cluster subsample, we find the following: (i) 63% are dominated by early-type galaxies (i.e., the late-type-poor clusters, f_L_<0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M_{sun}_) of 22+/-1 and 12.91+/-0.04, respectively; and (ii) 37% are dominated by late-type galaxies (i.e., the late-type-rich clusters, f_L_>=0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M_{sun}_) of 15.7+/-0.9 and 12.66+/-0.07, respectively. The statistical analysis of the late-type fraction distribution supports, with a 3{sigma} confidence level, the presence of two population components. It is suggested that the late-type-poor galaxy systems reflect and extend the class of Abell-APM-EDCC clusters and that the late-type-rich systems (~one-third of the total) belong to a new, previously unappreciated class. The late-type-rich clusters, on average high mass-to-light ratio systems, appear to be more clustered on large scales than the late-type-poor clusters. A class of late-type-rich clusters is not predicted by current theory.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/358
- Title:
- Ae/Be stars of Magellanic Bridge in JHKs
- Short Name:
- J/ApJ/658/358
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near-infrared camera SIRIUS and the 1.4m telescope IRSF, we surveyed ~3.0{deg}x1.3{deg} (24{deg}<~RA<~36{deg}, -75.0{deg}<~DE<~-73.7{deg}) in the J, H, and Ks bands. On the basis of colors and magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering the contaminations by miscellaneous sources, such as foreground stars and early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (#40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/38
- Title:
- AEGIS: demographics of X-ray and optical AGN
- Short Name:
- J/ApJ/728/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a new diagnostic method to classify galaxies into active galactic nucleus (AGN) hosts, star-forming galaxies, and absorption-dominated galaxies by combining the [OIII]/H{beta} ratio with rest-frame U-B color. This can be used to robustly select AGNs in galaxy samples at intermediate redshifts (z<1). We compare the result of this optical AGN selection with X-ray selection using a sample of 3150 galaxies with 0.3<z<0.8 and I_AB_<22, selected from the DEEP2 Galaxy Redshift Survey and the All-wavelength Extended Groth Strip International Survey. Among the 146 X-ray sources in this sample, 58% are classified optically as emission-line AGNs, the rest as star-forming galaxies or absorption-dominated galaxies. The latter are also known as "X-ray bright, optically normal galaxies" (XBONGs).
