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1381. The ELM survey. VII. 15 new ELM white dwarf cand.
ID:
ivo://CDS.VizieR/J/ApJ/818/155
Title:
The ELM survey. VII. 15 new ELM white dwarf cand.
Short Name:
J/ApJ/818/155
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 15 extremely low-mass (5<logg<7) white dwarf (WD) candidates, 9 of which are in ultra-compact double-degenerate binaries. Our targeted extremely low-mass Survey sample now includes 76 binaries. The sample has a lognormal distribution of orbital periods with a median period of 5.4hr. The velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 M_{sun}_ mean and 0.25M_{sun}_ dispersion. Thus extremely low-mass WDs are found in binaries with a typical mass ratio of 1:4. Statistically speaking, 95% of the WD binaries have a total mass below the Chandrasekhar mass, and thus are not type Ia supernova progenitors. Yet half of the observed binaries will merge in less than 6Gyr due to gravitational wave radiation; probable outcomes include single massive WDs and stable mass transfer AM CVn binaries.
1382. The ELM survey. VI. 11 new ELM WD binaries
ID:
ivo://CDS.VizieR/J/ApJ/812/167
Title:
The ELM survey. VI. 11 new ELM WD binaries
Short Name:
J/ApJ/812/167
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 11 new double degenerate systems containing extremely low-mass white dwarfs (ELM WDs). Our radial velocity observations confirm that all of the targets have orbital periods <=1 day. We perform spectroscopic fits and provide a complete set of physical and binary parameters. We review and compare recent evolutionary calculations and estimate that the systematic uncertainty in our mass determinations due to differences in the evolutionary models is small (~0.01M_{sun}_). Five of the new systems will merge due to gravitational wave radiation within a Hubble time, bringing the total number of merger systems found in the ELM Survey to 38. We examine the ensemble properties of the current sample of ELM WD binaries, including the period distribution as a function of effective temperature, and the implications for the future evolution of these systems. We also revisit the empirical boundaries of instability strip of ELM WDs and identify new pulsating ELM WD candidates. Finally, we consider the kinematic properties of our sample of ELM WDs and estimate that a significant fraction of the WDs from the ELM Survey are members of the Galactic halo.
1383. The ELM survey. V. White dwarf binaries
ID:
ivo://CDS.VizieR/J/ApJ/769/66
Title:
The ELM survey. V. White dwarf binaries
Short Name:
J/ApJ/769/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 17 low-mass white dwarfs (WDs) in short-period (P<=1 day) binaries. Our sample includes four objects with remarkable logg=~5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or ongoing accretion. Notably, six of the WDs in our sample have binary merger times <10Gyr. Four have >~0.9M_{sun}_ companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be millisecond pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the Extremely low mass (ELM) Survey to 54; 31 of these binaries will merge within a Hubble time.
1384. The evolutionary status of GK subgiants
ID:
ivo://CDS.VizieR/J/AJ/157/177
Title:
The evolutionary status of GK subgiants
Short Name:
J/AJ/157/177
Date:
21 Oct 2021
Publisher:
CDS
Description:
Snowden & Young (2005ApJS..157..126S) suggested that the reason why there are GK subgiants is because they are members of binaries, which would bring them above the main sequence in an Hertzsprung-Russell (HR) diagram. They studied a sample of 30 G0-K1 IV stars and were disappointed to find only two to be spectroscopic binaries. With more accurate radial velocities I found seven binaries in their samples of subgiants and control stars; orbital elements are given for those seven. Using Hipparcos parallaxes and SIMBAD data, I found that nearly all of the G0-K1 IV stars fall on the evolutionary tracks by Girardi et al. (2000, J/A+AS/141/371) for Population I stars with masses of 0.9-1.9 M_{sun}_ and ages of up to 10^10^ yr, which are normal parameters for nearby field stars. Therefore there is no problem regarding the existence of GK subgiants.
1385. The Extended Virgo Cluster Catalog (EVCC)
ID:
ivo://CDS.VizieR/J/ApJS/215/22
Title:
The Extended Virgo Cluster Catalog (EVCC)
Short Name:
J/ApJS/215/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725deg^2^ or 60.1Mpc^2^. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000km/s. In addition, 265 galaxies that have been overlooked in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies, 676 of which are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of optical images and a characterization of galaxies from their spectroscopic features. SDSS u, g, r, i, and z passband photometry of all EVCC galaxies was performed using Source Extractor. We compare the EVCC galaxies with the VCC in terms of morphology, spatial distribution, and luminosity function. The EVCC defines a comprehensive galaxy sample covering a wider range in galaxy density that is significantly different from the inner region of the Virgo cluster. It will be the foundation for forthcoming galaxy evolution studies in the extended Virgo cluster region, complementing ongoing and planned Virgo cluster surveys at various wavelengths.
1386. The globular cluster system of NGC 4636
ID:
ivo://CDS.VizieR/J/ApJ/709/377
Title:
The globular cluster system of NGC 4636
Short Name:
J/ApJ/709/377
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy NGC 4636 in the Virgo Cluster. We selected target GC candidates using the Washington photometry derived from the deep CCD images taken at the KPNO 4m Telescope. Then we obtained the spectra of 164 target objects in the field of NGC 4636 using the Multi-Object Spectroscopy mode of Faint Object Camera and Spectrograph on the Subaru 8.2m Telescope. We have measured the velocities for 122 objects: 105 GCs in NGC 4636, the nucleus of NGC 4636, 11 foreground stars, two background galaxies, and three probable intracluster GCs in the Virgo Cluster. The GCs in NGC 4636 are located in the projected galactocentric radius within 10' (corresponding to 43kpc). The measured velocities for the GCs range from ~300km/s to ~1600km/s, with a mean value of 932^+25^_-22_km/s, which is in good agreement with the velocity for the nucleus of NGC 4636, 928+/-45km/s.
1387. The Hamburg/SAO Survey for BCGs. I.
ID:
ivo://CDS.VizieR/J/A+A/397/463
Title:
The Hamburg/SAO Survey for BCGs. I.
Short Name:
J/A+A/397/463
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the description and the first results of a new project devoted to the search for extremely metal-deficient blue compact/HII-galaxies (BCGs) and to the creation of a well selected large BCG sample with strong emission lines. Such galaxies should be suitable for reliable determination of their oxygen abundance through the measurement of the faint [OIII]4363{AA} line. The goals of the project are two-fold: a) to discover a significant number of new extremely metal-poor galaxies (Z<=1/20Z_{sun}_), and b) to study the metallicity distribution of local BCGs. Selection of candidates for follow-up slit spectroscopy is performed on the database of objective prism spectra of the Hamburg Quasar Survey. The sky region is limited by {delta}>=0{deg} and b^II^<=-30{deg}. In this paper we present the results of the follow-up spectroscopy conducted with the Russian 6m telescope. The list of observed candidates contained 52 objects, of which 46 were confirmed as strong-lined BCGs (EW([OIII]5007>=100{AA}). The remaining five lower excitation ELGs include three BCGs, and two galaxies classified as SBN (Starburst Nucleus) and DANS (Dwarf Amorphous Nucleus Starburst). One object is identified as a quasar with a strong Ly_alpha emission line near {lambda}=5000{AA} (z~3). We provide a list with coordinates, measured radial velocities, B-magnitudes, equivalent widths EW([OIII]5007) and EW(H{beta}) and for the 46 strong-lined BCGs the derived oxygen abundances 12+log(O/H). The abundances range between 7.42 and 8.4 (corresponding to metallicities between 1/30 and 1/3Z_{sun}_). The sample contains four galaxies with Z<=1/20Z_{sun}_, of which three are new discoveries. This demonstrates the high efficiency of the new project to find extremely metal-deficient galaxies. The radial velocities of the strong-lined ELGs range between 500 and 19000km/s with a median value of ~6400km/s. The typical B-magnitudes of the galaxies presented are 17.0mag-18.0mag.
1388. The Hamburg/SAO Survey for ELGs
ID:
ivo://CDS.VizieR/J/A+AS/135/511
Title:
The Hamburg/SAO Survey for ELGs
Short Name:
J/A+AS/135/511
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present first results of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO - Special Astrophysical Observatory, Russia) which is based on the digitized objective-prism photoplates database of the Hamburg Quasar Survey (HQS). The main goal of this survey is the search for emission-line galaxies (ELG) in order to create a new deep sample of blue compact galaxies (BCG) in a large sky area. Another important goal of this work is to search for new extremely low-metallicity galaxies. We present the first results of spectroscopy obtained with the 2.2m telescope at the German-Spanish Observatory at Calar Alto, and with the 6m telescope at the Russian Special Astrophysical Observatory. The primary ELG candidate selection criteria applied were a blue continuum (near 4000{AA}) and the presence of emission lines close to 5000A recognized on digitized prism spectra of galaxies with magnitudes in the range B =16.0-19.5. The spectroscopy resulted in the detection or/and quantitative spectral classification of 74 emission-line objects. Of them 55 are newly discovered, and 19 were already known as galaxies before. 11 of the latter have redshifts and are known ELGs. For most of the known galaxies emission line ratios were measured for the first time and an improved classification is presented. 47 objects are classified as BCGs, one as Sy2 galaxy, six as probable LINERs, and four as new QSOs. The remaining galaxies do not show significant H{beta} and [OIII]4959,5007{AA} emission lines, and are likely either low-ionization starburst or dwarf amorphous nuclear starburst galaxies.
1389. The HIZOA-S survey
ID:
ivo://CDS.VizieR/J/AJ/151/52
Title:
The HIZOA-S survey
Short Name:
J/AJ/151/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
A blind HI survey of the extragalactic sky behind the southern Milky Way has been conducted with the multibeam receiver on the 64m Parkes radio telescope. The survey covers the Galactic longitude range 212{deg}<l<36{deg} and Galactic latitudes |b|<5{deg} to an rms sensitivity of 6mJy per beam per 27km/s channel and yields 883 galaxies to a recessional velocity of 12000km/s. The survey covers the sky within the HI Parkes All-Sky Survey (HIPASS) area to greater sensitivity, finding lower HI mass galaxies at all distances, and probing more completely the large-scale structures at and beyond the distance of the Great Attractor. Fifty-one percent of the HI detections have an optical/near-infrared (NIR) counterpart in the literature. A further 27% have new counterparts found in existing, or newly obtained, optical/NIR images. The counterpart rate drops in regions of high foreground stellar crowding and extinction, and for low HI mass objects. Only 8% of all counterparts have a previous optical redshift measurement. The HI sources are found independently of Galactic extinction, although the detection rate drops in regions of high Galactic continuum. The survey is incomplete below a flux integral of approximately 3.1Jy/km/s and mean flux density of approximately 21mJy, with 75% and 81% of galaxies being above these limits, respectively. Taking into account dependence on both flux and velocity width, and constructing a scaled dependence on the flux integral limit with velocity width (w^0.74^), completeness limits of 2.8Jy/km/s and 17mJy are determined, with 92% of sources above these limits. A notable new galaxy is HIZOA J1353-58, a possible companion to the Circinus galaxy. Merging this catalog with the similarly conducted northern extension, large-scale structures are delineated, including those within the Puppis and Great Attractor regions and the Local Void. Several newly identified structures are revealed here for the first time. Three new galaxy concentrations (NW1, NW2, and NW3) are key in confirming the diagonal crossing of the Great Attractor Wall between the Norma Cluster and the CIZA J1324.7-5736 cluster. Further contributors to the general mass overdensity in that area are two new clusters (CW1 and CW2) in the nearer Centaurus Wall, one of which forms part of the striking 180{deg} (100h^-1^Mpc) long filament that dominates the southern sky at velocities of ~3000 km/s, and the suggestion of a further wall at the Great Attractor distance at slightly higher longitudes.
1390. The kinematics of the C II {lambda}6578 line in PNe
ID:
ivo://CDS.VizieR/J/AJ/153/140
Title:
The kinematics of the C II {lambda}6578 line in PNe
Short Name:
J/AJ/153/140
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present spectroscopic observations of the C II {lambda}6578 permitted line for 83 lines of sight in 76 planetary nebulae at high spectral resolution, most of them obtained with the Manchester Echelle Spectrograph on the 2.1 m telescope at the Observatorio Astronomico Nacional on the Sierra San Pedro Martir. We study the kinematics of the C II {lambda}6578 permitted line with respect to other permitted and collisionally excited lines. Statistically, we find that the kinematics of the C II {lambda}6578 line are not those expected if this line arises from the recombination of C^2+^ ions or the fluorescence of C^+^ ions in ionization equilibrium in a chemically homogeneous nebular plasma, but instead its kinematics are those appropriate for a volume more internal than expected. The planetary nebulae in this sample have well-defined morphology and are restricted to a limited range in H{alpha} line widths (no large values) compared to their counterparts in the Milky Way bulge; both these features could be interpreted as the result of young nebular shells, an inference that is also supported by nebular modeling. Concerning the long-standing discrepancy between chemical abundances inferred from permitted and collisionally excited emission lines in photoionized nebulae, our results imply that multiple plasma components occur commonly in planetary nebulae.

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