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2671. OB associations in IC 1613
ID:
ivo://CDS.VizieR/J/A+A/502/1015
Title:
OB associations in IC 1613
Short Name:
J/A+A/502/1015
Date:
21 Oct 2021
Publisher:
CDS
Description:
Determining the parameters of massive stars is crucial to understand many processes in galaxies and the Universe, since these objects are important sources of ionization, chemical enrichment and momentum. 10m class telescopes enable us to perform detailed quantitative spectroscopic analyses of massive stars in other galaxies, sampling areas of different metallicity. Relating the stars to their environment is crucial to understand the physical processes ruling their formation and evolution. In preparation for the new instrumentation planned for the Gran Telescopio CANARIAS (GTC), our goal is to build a list of massive star candidates in the metal-poor irregular galaxy IC 1613. The catalogue must have very high astrometric accuracy, suitable for the current generation of multi-object spectrographs. A census of OB associations in this galaxy is also needed, to provide important additional information about the age and environment of the candidate OB stars.
2672. OB associations in M31
ID:
ivo://CDS.VizieR/J/ApJS/98/595
Title:
OB associations in M31
Short Name:
J/ApJS/98/595
Date:
21 Oct 2021
Publisher:
CDS
Description:
Images of the central and southern parts of the local group Sb spiral galaxy M31 were obtained by the Ultraviolet Imaging Telescope during the Astro-1 Spacelab mission. Stellar photometry is obtained for 611 stars in 59 van den Bergh associations in the near-UV A1 band (central wavelength 2490A), and for 130 of these stars in the far-UV B1 band (central wavelength 1520A). In addition, B-band magnitudes for 456 of the stars in ~30 associations, together with U- and R-band photometry for ~290 stars in ~15 associations are determined from CCD images. B-magnitudes from the catalog of Magnier et al. (1992A&AS...96..379M) are given for 137 stars and R-magnitudes for 233 stars. Stellar positions are obtained from the ground-based CCD images and from UIT images. Total fluxes in the UV bands are measured for 63 associations. Finding charts are presented in the NUV and FUV bands, as well as one optical band. Tables give the images utilized in this investigation, the associations observed, with positions, total UV fluxes, extinctions estimated from color-magnitude diagrams, and stellar positions with photometry in up to five bands. UV color magnitude diagrams are presented with extinctions estimated by comparing the observed association color magnitude diagrams with colors and magnitudes of early-type stars computed from the IUE spectral atlas of Fanelli et al. (1992ApJS...82..197F). Comparison with evolutionary models suggests a maximum initial mass ~85M_{sun}_. Ultraviolet extinction within most M31 OB associations is found to follow an extinction curve similar to that of Hutchings et al. (1992ApJ...400L..35H). The variation in the fraction of near-UV stars also measured in the far-UV among the associations is probably caused by variations in age, extinction, and the degree of foreground contamination.
2673. OB associations in NGC 7793
ID:
ivo://CDS.VizieR/J/A+A/440/783
Title:
OB associations in NGC 7793
Short Name:
J/A+A/440/783
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the results from application of an objective algorithm (PLC) to find OB associations, to B and V images of the Sculptor spiral galaxy NGC 7793, which were obtained with the ESO VLT and FORS instrument and basically cover the entire spatial extent of the galaxy. We detected 148 associations. Statistical tests show that less than 6 of these detections are caused by randomly concentrated blue stars. In the size distribution, a sharp peak is observed at a value of about 35 microradians, which corresponds to a linear diameter of 135pc, assuming a distance of 3.91Mpc to the galaxy. We also find 25 much larger objects. A second application of the PLC technique shows that 20 of them are stellar complexes consisting of multiple sub-associations with typical sizes on the order of 130pc. A comparison of the size distribution of the detected OB associations in NGC 7793 with observed distributions in other galaxies suggests that the conditions in two Sculptor Group galaxies (NGC 300 and NGC 7793) favour the formation of large associations. We provide a catalog giving coordinates and physical parameters for all the associations and stellar complexes we have found in our survey.
2674. Objective-prism survey of em. objects in M31
ID:
ivo://CDS.VizieR/J/A+AS/102/251
Title:
Objective-prism survey of em. objects in M31
Short Name:
J/A+AS/102/251
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using GRENS plates taken at the Canada-France-Hawaii telescope, we have searched almost the whole extent of M31 for small-diameter objects with strong emission lines. Most are planetary nebulae candidates, but there are also many Wolf-Rayet star candidates and small HII regions or compact parts of large HII regions. A catalogue is presented with a cross-identification with previous catalogues. Many new planetary nebulae and Wolf-Rayet candidates are found. Their distribution is compared with those of other tracers in M31. In particular the distribution of planetary nebulae candidates is compared with that of the integrated blue light and we confirm the result obtained by Jacoby ( 1980ApJS...42....1J) and Ciardullo et al. (1989ApJ...339...53C): the number of planetary nebulae per unit total luminosity is a constant throughout the disk of M31. The Wolf- Rayet star candidates are concentrated in the well-known ring of star formation; their total number is estimated as 300 within the limit of detection of the deepest existing surveys, but this may still be an underestimate of the true number.
2675. Objects of 1988 Zenith Sky Survey
ID:
ivo://CDS.VizieR/J/AZh/71/352
Title:
Objects of 1988 Zenith Sky Survey
Short Name:
J/AZh/71/352
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of optical identification of radio sources Zenith Sky Survey with the Palomar Sky Survey prints are presented. The sky survey was conducted with a RATAN-600 radio telescope at 8.0cm in a ring-aperture operation mode. All the objects belong to the radio source population with flux densities in a range from 5 to 50mJy. The mean value of the spectral index distribution for the sources identified with other catalogs was found to be equal to -0.9 at 8.0cm.
2676. Obscured active galaxies
ID:
ivo://CDS.VizieR/J/ApJ/702/441
Title:
Obscured active galaxies
Short Name:
J/ApJ/702/441
Date:
21 Oct 2021
Publisher:
CDS
Description:
Obscured or narrow-line active galaxies offer an unobstructed view of the quasar environment in the presence of a luminous and vigorously accreting black hole (BH). We exploit the large new sample of optically selected luminous narrow-line active galaxies from the Sloan Digital Sky Survey at redshifts 0.1<z<0.45, in conjunction with follow-up observations with the Low Dispersion Survey Spectrograph (LDSS3) at Magellan, to study the distributions of BH mass and host galaxy properties in these extreme objects.
2677. Obscured AGNs from XMM-Newton and AKARI
ID:
ivo://CDS.VizieR/J/ApJ/814/11
Title:
Obscured AGNs from XMM-Newton and AKARI
Short Name:
J/ApJ/814/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90{mu}m) sources located at |b|>10{deg} to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2-4.5keV and 4.5-12keV bands >-0.1 and (2) EPIC-PN count rate (CR) in the 0.2-12keV to infrared flux ratio CR/F_90_<0.1 or CR/F_18_<1 where F_18_ and F_90_ are infrared fluxes at 18 and 90{mu}m in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of N_H_~10^22-24^/cm2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of >700eV is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18{mu}m condition is used. Of the 26 objects, 4 are optically classified as an HII nucleus and are new "elusive AGNs" in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.
2678. Observational comparison between ULXs and XRBs
ID:
ivo://CDS.VizieR/J/ApJ/687/471
Title:
Observational comparison between ULXs and XRBs
Short Name:
J/ApJ/687/471
Date:
21 Oct 2021
Publisher:
CDS
Description:
To test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting intermediate-mass black holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample with the highest quality data in the Chandra archive. We establish as a general property of ULXs that the most X-ray-luminous objects possess the flattest X-ray spectra (in the Chandra bandpass). No prior sample studies have established the general hardening of ULX spectra with luminosity. This hardening occurs at the highest luminosities (absorbed luminosity >=5x10^39^erg/s) and is in line with recent models arguing that ULXs are actually stellar mass black holes. From spectral modeling, we show that the evidence originally taken to mean that ULXs are IMBHs - i.e., the "simple IMBH model" - is nowhere near as compelling when a large sample of ULXs is looked at properly. During the last couple of years, XMM-Newton spectroscopy of ULXs has to a large extent begun to negate the simple IMBH model based on fewer objects. We confirm and expand these results, which validates the XMM-Newton work in a broader sense with independent X-ray data.
2679. Observation & modelling for radio-loud AGN
ID:
ivo://CDS.VizieR/J/MNRAS/453/2682
Title:
Observation & modelling for radio-loud AGN
Short Name:
J/MNRAS/453/2682
Date:
21 Oct 2021
Publisher:
CDS
Description:
The interactions between radio-loud AGN and their environments play an important role in galaxy and cluster evolution. Recent work has demonstrated fundamental differences between high- and low-excitation radio galaxies (HERGs and LERGs), and shown that they may have different relationships with their environments. In the Chandra Large Project ERA (Environments of Radio-loud AGN), we made the first systematic X-ray environmental study of the cluster environments of radio galaxies at a single epoch (z~0.5), and found tentative evidence for a correlation between radio luminosity and cluster X-ray luminosity. We also found that this relationship appeared to be driven by the LERG subpopulation. We have now repeated the analysis with a low-redshift sample (z~0.1), and found strong correlations between radio luminosity and environment richness and between radio luminosity and central density for the LERGs but not for the HERGs. These results are consistent with models in which the HERGs are fuelled from accretion discs maintained from local reservoirs of gas, while LERGs are fuelled more directly by gas ingested from the intracluster medium. Comparing the samples, we found that although the maximum environment richness of the HERG environments is similar in both samples, there are poorer HERG environments in the z~0.1 sample than in the z~0.5 sample. We have therefore tentative evidence of evolution of the HERG environments. We found no differences between the LERG subsamples for the two epochs, as would be expected if radio and cluster luminosities are related.
2680. Observation of 57 spirals
ID:
ivo://CDS.VizieR/J/A+AS/116/15
Title:
Observation of 57 spirals
Short Name:
J/A+AS/116/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we present short H I synthesis observations of 57 galaxies without H I information in the RC3. These are a by-product of a large survey with the WSRT of the neutral hydrogen gas in spiral and irregular galaxies. Global profiles and related quantities are given for the 42 detected galaxies and upper limits for the remaining 15. A number of galaxies have low values of H I mass-to-blue luminosity ratio.

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