- ID:
- ivo://CDS.VizieR/J/MNRAS/396/818
- Title:
- Blue early-type galaxies in Galaxy Zoo
- Short Name:
- J/MNRAS/396/818
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a population of nearby, blue early-type galaxies with high star formation rates (0.5<SFR<50M_{sun}_/yr). They are identified by their visual morphology as provided by Galaxy Zoo for Sloan Digital Sky Survey Data Release 6 and their u-r colour. We select a volume-limited sample in the redshift range 0.02<z<0.05, corresponding to luminosities of approximately L* and above and with u-r colours significantly bluer than the red sequence. We confirm the early-type morphology of the objects in this sample and investigate their environmental dependence and star formation properties.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/140/309
- Title:
- Blue-H{alpha} objects in M33
- Short Name:
- J/A+AS/140/309
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the purposes of a search for SS433 type objects, LBV stars and hypergiants in M33, we have carried out a photometry of blue stars in H{alpha} images of this galaxy. From 2332 listed OB stars, we have isolated 549 objects, which have H{alpha} excess over stars of the same V magnitude. Among them 81 emission stars (s) have been selected. About 60% of isolated objects found to be extended in H{alpha}, among them 154 diffuse (d) and 180 bubble-type (b) nebulae. 117 objects are compact (c) and faint H{alpha} sources. These groups are different in colour indices, H{alpha} fluxes, surface brightness and sizes. The most probable size of the H{alpha} nebulae is FWHM=10-14pc. There is evidence that their properties and location in the galaxy are defined by interstellar gas pressure and related to spiral arms. The d objects are HII regions with an embedded star. The b objects are probably envelopes around WR stars or SN remnants. Among s-type objects we isolated a group of 20 brightest stars, which in their average properties fit well to the parameters of blue hypergiants or LBV-type stars. The stars of intermediate brightness follow very well to blue Ia supergiants. The interstellar absorption derived from brightest H{alpha} stars is A_V_=0.93+/-0.05mag. We classify the faintest stars as blue Ib supergiants, their average absorption is A_V_~0.6mag. They are restricted in number by the limiting stellar magnitude in the original sample.
1943. Blue HB stars in SDSS
- ID:
- ivo://CDS.VizieR/J/AJ/127/899
- Title:
- Blue HB stars in SDSS
- Short Name:
- J/AJ/127/899
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We isolate samples of 733 bright (g<18) and 437 faint (g>18) high Galactic latitude blue horizontal-branch stars with photometry and spectroscopy in the Sloan Digital Sky Survey (SDSS). Comparison of independent photometric and spectroscopic selection criteria indicates that contamination from F and blue straggler stars is less than 10% for bright stars (g<18) and about 25% for faint stars (g>18), and this is qualitatively confirmed by proper motions based on the USNO-A (<I/252>) catalog as first epoch. Analysis of repeated observations shows that the errors in radial velocity are ~26km/s. A relation between absolute magnitude and color is established using the horizontal branches of halo globular clusters observed by SDSS. Bolometric corrections and colors are synthesized in the SDSS filters from model spectra. The redder stars agree well in absolute magnitude with accepted values for RR Lyrae stars. The resulting photometric distances are accurate to about 0.2mag, with a median of about 25kpc. Modest clumps in phase space exist and are consistent with the previously reported tidal stream of the Sagittarius dwarf galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/108/1722
- Title:
- Blue horizontal branch stars
- Short Name:
- J/AJ/108/1722
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete sample of blue horizontal branch (BHB) stars in the magnitude range 13.0<V<16.5 is isolated in two Galactic fields that have previously been searched for RR Lyrae variables: SA 57 in the Northern Polar Cap and the Lick Astrograph field RR 7 in the Anticenter (l=183{deg}, b=+37{deg}). These BHB stars are a subset of the AF stars found in the Case Low-Dispersion Northern Survey; lists of these AF stars were made available by the late Nick Sanduleak. The completeness of the sample was confirmed by reference to the photometric survey of SA 57 by Stobie & Ishida (1987AJ93..... 624S) that is complete to fainter than V=18. In the color range 0.00<(B-V)_0_<+0.20, we can distinguish the BHB stars among these AF stars by comparing them both with well known local field horizontal branch (FHB) stars and also the BHB members of the halo globular clusters M3 and M92. The criteria for this comparison include (1) a (u-B)_K_ color index (derived from photoelectric observations using the Stromgren u filter and the Johnson B and V filters) that measures the size of the Balmer jump, (2) a spectrophotometric index A that measures the steepness of the Balmer jump, and (3) a parameter D_0.2_ that is the mean width of the H{gamma} and H{delta} Balmer lines measured at 20 percent of the continuum level. These criteria give consistent results in separating BHB stars from higher gravity main sequence AF stars in the color range 0.00<(B-V)_0_<+0.20. All three photometric and spectrophotometric criteria were measured for 35 stars in the SA 57 field and 37 stars in the RR 7 field that are in the color range (B-V)_0_<+0.23 and in the magnitude range 13.0<V<16.5. For a small number of additional stars only (u-B)_K_ was obtained. Among the AF stars that are fainter than B=13 and bluer than (B-V)_0_=+0.23, about half of those in the SA 57 field and about one third of those in the lower latitude RR 7 field are BHB stars. Isoabundance contours were located empirically in plots of the pseudoequivalent width versus (B-V)_0_ for the lines of Mg II A4481{AA}, Ca II A3933 {AA} and Fe I A4272{AA}. Solar abundances were defined by the data from main sequence stars in the Pleiades and Coma open clusters. Data from the BHB stars in M3 and M92 defined the [Fe/H]=1.5 and -2.2 isoabundance contours, respectively. Metallicities of all stars were estimated by interpolating the measured pseudoequivalent widths in these diagrams at the observed (B-V)_0_. The distribution of [Fe/H] found for the BHB stars in this way is very similar to that which we found for the RR Lyrae stars in the same fields using the Preston AS method. The space densities of these BHB stars were analyzed both separately and together with earlier observations of field BHB stars given by Arnold & Gilmore (1992MNRAS.257..225A), Sommer-Larsen & Christensen (1986MNRAS.219..537S), and Preston et al. (1991ApJ...375..121P). This analysis supports a two-component model for the halo of our Galaxy that is similar in many respects to that proposed by Hartwick [The Galaxy (Reidel, Dordrecht 1987)] although our discussion refers only to the region outside the solar circle. For Z>=35kpc, a classical spherical halo dominates which follows a R_gal_^-3.5^ space-density law and which has a HB morphology like that of the globular cluster M3 (i.e., approximately equal numbers of BHB and RR Lyrae stars). Closer to the galactic plane, there is an additional component with a much flatter galactic distribution (scale height ~2.2kpc near the Sun). The stars of the two components do not have significantly different metallicity distributions but do have slightly different distributions of the A parameter which measures the steepness of the Balmer jump; this is the only physical criterion (independent of spatial or kinematic considerations) which distinguishes between the two components. If present estimates of the local RR Lyrae star space density are correct, then the ratio of BHB stars to RR Lyrae stars is higher in the flatter halo component. The flat component would then have a bluer HB morphology (which could be interpreted as making it older) than the spherical component. In the solar neighborhood about 80 percent of the BHB stars come from the flat component and about 20 percent from the spherical component. More than half of the AF stars with V>13.0 and (B-V)_0_<+0.23 are not BHB stars but have surface gravities that are more like those expected for main sequence stars. Their measured metallicities lie in the range -0.2<[Fe/H]<-2.3. The more metal-poor of these stars are probably similar to the blue metal-poor stars that have been discussed by Preston et al. (1994AJ....108..538P) which, while they probably include globular cluster blue stragglers as a subset, must also comprise stars of other types.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/171
- Title:
- Blue horizontal branch stars catalog
- Short Name:
- J/A+AS/109/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/334/987
- Title:
- 6 blue objects spectral data
- Short Name:
- J/A+A/334/987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a programme to investigate spatial variations in the Galactic chemical composition, we have been searching for normal B-type stars and A-type supergiants near the Galactic center. During this search we have found eleven peculiar stars, and in some cases performed detailed abundance analyses of them which suggest that they may be at a post-AGB evolutionary stage. The A-type post-AGB candidates show [Fe/H]=-1.0 to -2.0, and [O/Fe]~+1.4, typical of the post-AGB abundance patterns discussed in the literature. One star, LS 3591 (=SAO 243756), has also been examined recently by Oudmaijer (1996A&A...306..823O); its spectrum appears to be changing very rapidly, which may indicate erratic mass loss or the incipient formation of a planetary nebula. A B-type post-AGB candidate, LS 4950, has a similar spectrum to a well studied post-AGB star, LSIV -12 111. However, an examination of the line strengths and elemental abundances of LS 4950 show that it is peculiar for both a PopulationII, post-AGB, B-type star and for a normal, PopulationI, B-type supergiant. Two other B-type stars, LS 4825 and LS 5112, are either post-AGB stars near the Galactic center or normal B-type supergiants lying well beyond the Galactic center. In addition, several Be-type stars have been newly (or more clearly) identified from our spectra.
- ID:
- ivo://CDS.VizieR/J/AJ/130/381
- Title:
- Blueshifted [O III] emission
- Short Name:
- J/AJ/130/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [OIII]{lambda}5007 line is commonly used as an indicator of the systemic redshift of active galactic nuclei (AGNs). Also, recent studies have used the width of this emission line as a proxy for the stellar velocity dispersion in the host galaxy. This paper calls both of these assumptions into question by analyzing a sample of approximately 400 AGN spectra from the first data release of the Sloan Digital Sky Survey.
- ID:
- ivo://CDS.VizieR/J/A+AS/91/171
- Title:
- Blue stars between Magellanic Clouds
- Short Name:
- J/A+AS/91/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of 1679 blue stars located in a region of the Southern sky between the Magellanic Clouds. Equatorial coordinates and photographic V and B-V are given for stars brighter than V=18.5. The instrumental magnitudes obtained from UKST IIIa-J and IIIa-F plates are calibrated with nearly 200 stars with CCD B and V observations. The list can be used for follow-ip identification, spatial distribution and other studies of young OB stars belonging to the Magellanic Clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A18
- Title:
- Blue stars with disk photometry in NGC 6611
- Short Name:
- J/A+A/521/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 and its parental cloud, the Eagle Nebula (M 16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. In our previous studies of the Eagle Nebula, we identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0um. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared.
- ID:
- ivo://CDS.VizieR/J/other/Ap/52.369
- Title:
- Blue stellar objects in strip DE=47{deg}
- Short Name:
- J/other/Ap/52.36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a list of 111 blue stellar objects and individual active galaxies with excess ultraviolet continuum lying within 08h-17h in {alpha} and +45{deg} +49{deg} in {delta} (1950.0). The surveyed objects are classified in terms of activity type.
