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4681. One-side head-tail (OHT) galaxies from FIRST & SDSS
ID:
ivo://CDS.VizieR/J/ApJS/254/30
Title:
One-side head-tail (OHT) galaxies from FIRST & SDSS
Short Name:
J/ApJS/254/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
One-side head-tail (OHT) galaxies are radio galaxies with a peculiar shape. They usually appear in galaxy clusters, but they have never been cataloged systematically. We design an automatic procedure to search for them in the Faint Images of the Radio Sky at Twenty-Centimeters source catalog and compile a sample with 115 HT candidates. After cross-checking with the Sloan Digital Sky Survey photometric data and catalogs of galaxy clusters, we find that 69 of them are possible OHT galaxies. Most of them are close to the center of galaxy clusters. The lengths of their tails do not correlate with the projection distance to the center of the nearest galaxy clusters, but show weak anticorrelation with the cluster richness, and are inversely proportional to the radial velocity differences between clusters and host galaxies. Our catalog provides a unique sample to study this special type of radio galaxies.
4682. One thousand new dwarf novae from the OGLE Survey
ID:
ivo://CDS.VizieR/J/AcA/65/313
Title:
One thousand new dwarf novae from the OGLE Survey
Short Name:
J/AcA/65/313
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present one of the largest collections of dwarf novae (DNe) containing 1091 objects that have been discovered in the long-term photometric data from the Optical Gravitational Lensing Experiment (OGLE) survey. They were found in the OGLE fields toward the Galactic bulge and the Magellanic Clouds. We analyze basic photometric properties of all systems and tentatively find a population of DNe from the Galactic bulge. We identify several dozen of WZ Sge-type DN candidates, including two with superhump periods longer than 0.09d. Other interesting objects include SU UMa-type stars with "early" precursor outbursts or a Z Cam-type star showing outbursts during standstills. We also provide a list of DNe which will be observed during the K2 Campaign 9 microlensing experiment in 2016. Finally, we present the new OGLE-IV real-time data analysis system: CVOM, which has been designed to provide continuous real time photometric monitoring of selected CVs.
4683. On the evolution of angular momentum
ID:
ivo://CDS.VizieR/J/other/RMxAA/56.139
Title:
On the evolution of angular momentum
Short Name:
J/other/RMxAA/56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Selecting the best quality data, I find that nearly all 0.5 to 1.2M_{sun}_ main sequence stars converge to a single rotational mass dependent sequence after 750Myr; when the mass is larger than 0.8M_{sun}_, most of them converge in ~120Myr. If stars rotate as rigid bodies, the angular momentum of the vast majority is within clearly outlined bounds. The lower boundary defines a terminal main sequence rotational isochrone, the upper one coincides with slow rotators from the Pleiades and stars from Praesepe delineate a third one. Mass dependent exponential relationships between angular momentum and age are determined from these isochrones. Age estimates based on the angular momentum, are acceptable in middle aged stars older than 750Myr and more massive than 0.6-0.7M_{sun}_. The evolution of the Rossby number indicates that the Parker dynamo may cease early on in stars where M/M_{sun}_>=1.1. An empirical formula for the torque, an idealized model for it and a relation between rotational period and magnetic field, lead to a formula for the evolution of the mass loss rate, predicting that the present solar rate is close to a minimum and that it was around five times more vigorous when life on Earth started.
4684. On the nature of small galaxy systems
ID:
ivo://CDS.VizieR/J/MNRAS/481/2458
Title:
On the nature of small galaxy systems
Short Name:
J/MNRAS/481/2458
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim at defining homogeneous selection criteria of small galaxy systems in order to build catalogues suitable to compare main properties of pairs, triplets, and groups with four or more members. To this end we use spectroscopic and photometric Sloan Digital Sky Survey (SDSS) data to identify systems with a low number of members. We study global properties of these systems and the properties of their member galaxies finding that galaxies in groups are systematically redder and with lower star formation activity indicators than galaxies in pairs which have a higher fraction of star-forming galaxies. Triplet galaxies present intermediate trends between pairs and groups. We also find an enhancement of star formation activity for galaxies in small systems with companions closer than 100kpc, irrespective of the number of members. We have tested these analyses on SDSS mock catalogues derived from the Millennium simulation, finding as conservative thresholds 76 per cent completeness and a contamination of 23 per cent in small galaxy systems, when considering an extreme case of incompleteness due to fiber collisions. Nevertheless, we also found that the results obtained are not likely affected by projection effects. Our studies suggest that an extra galaxy in a system modify the properties of the member galaxies. In pairs, galaxy-galaxy interactions increase gas density and trigger starbursts. However, repeated interactions in triplets and groups can generate gas stripping, turbulence, and shocks quenching the star formation in these systems.
4685. Oosterhoff dichotomy in Galactic bulge
ID:
ivo://CDS.VizieR/J/MNRAS/484/4833
Title:
Oosterhoff dichotomy in Galactic bulge
Short Name:
J/MNRAS/484/4833
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the Oosterhoff (Oo) dichotomy in the Galactic bulge using 8141 fundamental-mode RR Lyrae stars. We used public photometric data from the Optical Gravitational Lensing Experiment and the Vista Variables in the Via Lactea survey. We carefully selected fundamental-mode stars without modulation and without association with any globular cluster located towards the Galactic bulge. Subsequently, we identified and separated the Oosterhoff groups I and II on the basis of their period-amplitude distribution and using a relation fitted to the Oosterhoff I locus. Both Oosterhoff groups were then compared to observations of two bulge globular clusters and with models of stellar pulsation and evolution. We found that some of the variables classified as Oo II belong to a third Oo group. The Oosterhoff II variables are more metal-poor on average, more massive, and cooler than their Oosterhoff I counterparts. The analysis of their spatial distribution shows a systematic difference between foreground, central, and background regions in the occurrence of the Oosterhoff II group. The difference between the Oo I and II groups is also seen in their distance distributions with respect to the Galactic bar, but neither group is associated with the bar.
4686. Open cluster King 1 photometry
ID:
ivo://CDS.VizieR/J/MNRAS/470/4285
Title:
Open cluster King 1 photometry
Short Name:
J/MNRAS/470/4285
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse the poorly studied open cluster King 1 in the second Galactic quadrant. From wide-field photometry, we have studied the spatial distribution of this cluster. We determined that the centre of King 1 is located at {alpha}_2000_=00:22 and {delta}_2000_=+64:23. By parameterizing the stellar density with a King profile, we have obtained a central density of {rho}_0_= 6.5+/-0.2star/arcmin^2^ and a core radius of r_core_=1.9+/-0.2arcmin. By comparing the observed colour-magnitude diagram of King 1 with those of similar open clusters and with different sets of isochrones, we have estimated an age of 2.8+/-0.3Gyr, a distance modulus of (m-M)_o_=10.6+/-0.1mag and a reddening of E(B-V)=0.80+/-0.05mag. To complete our analysis, we acquired medium resolution spectra for 189 stars in the area of King 1. From their derived radial velocities, we determined an average velocity <V_r_>=-53.1+/-3.1km/s. From the strength of the infrared CaII lines in red giants we have determined an average metallicity of <[M/H]>=+0.07+/-0.08dex. From spectral synthesis, we have also estimated an {alpha}-elements abundance of <[{alpha}/M]>=-0.10+/-0.08dex.
4687. Open cluster Pis 20
ID:
ivo://CDS.VizieR/J/A+AS/111/85
Title:
Open cluster Pis 20
Short Name:
J/A+AS/111/85
Date:
21 Oct 2021
Publisher:
CDS
Description:
The very young open cluster Pis 20 has been investigated using CCD UBVR photometry. New blue faint members were found down to V=19mag. With them we obtain a better definition of the lower cluster main sequence. Using the fitting method, we derive a cluster distance of d=3600pc (V_0_-M_V_=12.80). The mean color excess is <E_B-V_>=1.24mag.
4688. Open clusters as galactic disk tracers. I.
ID:
ivo://CDS.VizieR/J/AJ/136/118
Title:
Open clusters as galactic disk tracers. I.
Short Name:
J/AJ/136/118
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have begun a survey of the chemical and dynamical properties of the Milky Way disk as traced by open star clusters. In this first contribution, the general goals of our survey are outlined and the strengths and limitations of using star clusters as a Galactic disk tracer sample are discussed. We also present medium-resolution (R~150000) spectroscopy of open cluster stars obtained with the Hydra multi-object spectrographs on the Cerro Tololo Inter-American Observatory 4m and WIYN 3.5m telescopes. Here we use these data to determine the radial velocities of 3436 stars in the fields of open clusters within about 3kpc, with specific attention to stars having proper motions in the Tycho-2 catalog. Additional radial velocity members (without Tycho-2 proper motions) that can be used for future studies of these clusters were also identified.
4689. Open clusters CCD photometry. I.
ID:
ivo://CDS.VizieR/J/A+AS/108/151
Title:
Open clusters CCD photometry. I.
Short Name:
J/A+AS/108/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
4690. Open clusters in Auriga OB2
ID:
ivo://CDS.VizieR/J/MNRAS/459/880
Title:
Open clusters in Auriga OB2
Short Name:
J/MNRAS/459/880
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the area around the HII region Sh 2-234, including the young open cluster Stock 8, to investigate the extent and definition of the association Aur OB2 and the possible role of triggering in massive cluster formation. We obtained Stromgren and J, H, Ks photometry for Stock 8 and Stromgren photometry for two other cluster candidates in the area, which we confirm as young open clusters and name Alicante 11 and Alicante 12. We took spectroscopy of ~33 early-type stars in the area, including the brightest cluster members. We calculate a common distance of 2.80+0.27-0.24kpc for the three open clusters and surrounding association. We derive an age 4-6Ma for Stock 8, and do not find a significantly different age for the other clusters or the association. The star LS V +34 23, with spectral type O8 II(f), is likely the main source of ionization of Sh 2-234. We observe an important population of pre-main-sequence stars, some of them with discs, associated with the B-type members lying on the main sequence. We interpret the region as an area of recent star formation with some residual and very localized ongoing star formation. We do not find evidence for sequential star formation on a large scale. The classical definition of Aur OB2 has to be reconsidered, because its two main open clusters, Stock 8 and NGC 1893, are not at the same distance. Stock 8 is probably located in the Perseus arm, but other nearby HII regions whose distances also place them in this arm show quite different distances and radial velocities and, therefore, are not connected.