- ID:
- ivo://CDS.VizieR/J/ApJ/525/127
- Title:
- RGB sample of BL Lacertae objects
- Short Name:
- J/ApJ/525/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining newly identified and previously known BL Lacertae objects from the ROSAT All-Sky Survey-Green Bank (RGB) catalog, we present a sample of 127 BL Lacertae objects, the largest ever derived from a single uniform survey. A complete sample of 33 objects brighter than O=18.0 mag is also presented. These samples are compared to other known BL Lac samples and are generally found to exhibit properties intermediate between those of the previously disparate classes of high- and low-energy-peaked BL Lacertae objects (HBLs and LBLs, respectively). This result is most dramatic in the distribution of the X-ray to radio logarithmic flux ratios, where the RGB BL Lacertae objects are shown to peak precisely where the sharp dichotomy between the two subclasses was previously seen.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/4315
- Title:
- RGB stars in NGC 6822, Ca II triplet
- Short Name:
- J/MNRAS/456/4315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the chemistry and kinematics of red giants in the dwarf irregular galaxy NGC 6822. Spectroscopy at ~8500{AA} was acquired for 72 red giant stars across two fields using FORS2 at the VLT. Line-of-sight extinction was individually estimated for each target star to accommodate the variable reddening across NGC 6822. The mean radial velocity was found to be <v_rad_>=-52.8+/-2.2km/s with dispersion {sigma}_v_=24.1km/s, in agreement with other studies. Ca ii triplet equivalent widths were converted into [Fe/H] metallicities using a V magnitude proxy for surface gravity. The average metallicity was <[Fe/H]>=-0.84+/-0.04 with dispersion {sigma}=0.31dex and interquartile range 0.48. Our assignment of individual reddening values makes our analysis more sensitive to spatial variations in metallicity than previous studies. We divide our sample into metal-rich and metal-poor stars; the former were found to cluster towards small radii with the metal-poor stars more evenly distributed across the galaxy. The velocity dispersion of the metal-poor stars was found to be higher than that of the metal-rich stars {sigma}_vMP_=27.4km/s; {sigma}_vMR_=21.1km/s); combined with the age-metallicity relation this indicates that the older populations have either been dynamically heated during their lifetimes or were born in a less disc-like distribution than the younger stars.. The low ratio v_rot_/{sigma}_v_ suggests that within the inner 10-arcmin, NGC 6822's stars are dynamically decoupled from the HI gas, and possibly distributed in a thick disc or spheroid structure.
- ID:
- ivo://CDS.VizieR/J/A+A/464/201
- Title:
- RGB stars in Sagittarius streams
- Short Name:
- J/A+A/464/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sagittarius (Sgr) dwarf spheroidal galaxy is currently being disrupted under the strain of the Milky Way. A reliable reconstruction of Sgr star formation history can only be obtained by combining core and stream information. We present radial velocities for 67 stars belonging to the Sgr Stream. For 12 stars in the sample we also present iron (Fe) and {alpha}-element (Mg, Ca) abundances.
- ID:
- ivo://CDS.VizieR/J/AJ/157/126
- Title:
- RGZ: distortion of radio galaxies by galaxy clusters
- Short Name:
- J/AJ/157/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the impact of cluster environment on the morphology of a sample of 4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the sample lies within a projected 15 Mpc of an optically identified cluster. Brightest cluster galaxies (BCGs) are more likely than other cluster members to be radio sources, and are also moderately bent. The surface density as a function of separation from cluster center of non-BCG radio galaxies follows a power law with index -1.10+/-0.03 out to 10 r_500_ (~7 Mpc), which is steeper than the corresponding distribution for optically selected galaxies. Non-BCG radio galaxies are statistically more bent the closer they are to the cluster center. Within the inner 1.5 r_500_ (~1 Mpc) of a cluster, non-BCG radio galaxies are statistically more bent in high-mass clusters than in low-mass clusters. Together, we find that non-BCG sources are statistically more bent in environments that exert greater ram pressure. We use the orientation of bent radio galaxies as an indicator of galaxy orbits and find that they are preferentially in radial orbits. Away from clusters, there is a large population of bent radio galaxies, limiting their use as cluster locators; however, they are still located within statistically overdense regions. We investigate the asymmetry in the tail length of sources that have their tails aligned along the radius vector from the cluster center, and find that the length of the inward-pointing tail is weakly suppressed for sources close to the center of the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A36
- Title:
- Rich clusters from SDSS DR8
- Short Name:
- J/A+A/542/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of the properties of galaxy clusters and their environment gives us information about the formation and evolution of galaxies, groups and clusters, and larger structures - superclusters of galaxies and the whole cosmic web. We study the relations between the multimodality of galaxy clusters drawn from the SDSS DR8 and the environment where they reside. As cluster environment we consider the global luminosity density field, supercluster membership, and supercluster morphology.
- ID:
- ivo://CDS.VizieR/VII/110A
- Title:
- Rich Clusters of Galaxies
- Short Name:
- VII/110A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is an all-sky catalog of 4073 rich clusters of galaxies, each having at least 30 members within the magnitude range m_3_ to m_3_ + 2 (m_3_ is the magnitude of the third brightest cluster member) and each with a nominal redshift less than 0.2. The southern data have been collected from a survey of UK 1.2 m Schmidt telescope IIIa-J plates and films and have been reduced to the systems defined by the northern data previously published by G.O. Abell. A revised northern catalog, including Bautz-Morgan types and redshifts where known, is also included.
- ID:
- ivo://CDS.VizieR/J/A+A/447/473
- Title:
- R I CN TiO photometry of DDO190 carbon stars
- Short Name:
- J/A+A/447/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out deep R, I, CN, TiO observations of the dwarf irregular galaxy DDO 190. We confirm the existence intermediate-age population around this galaxy. The identification of 47 carbon stars seen up to 5 arcmin from the centre of the galaxy implies that the population distribution of DDO 190 is similar to those found in some other Local Group dIrr galaxies. An estimate of the metallicity, [Fe/H]=-1.55+/-0.12, is obtained based on the observed C/M ratio. From the analysis of star counts, corrected for the radial variation of the incompleteness level, we determine a scale-length {alpha}=40+/-5", in agreement with the recent literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1587
- Title:
- RIK photometry of far-IR sources in NGP
- Short Name:
- J/MNRAS/401/1587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present follow-up observations of the far-infrared (FIR) sources at 90, 150 and 180um detected as part of the ISOPHOT EBL project, which has recently measured the absolute surface brightness of the cosmic infrared background (CIRB) radiation for the first time independently from COBE data. We have observed the fields at the North Galactic Pole region in the optical and near-IR, and complement these data with Sloan Digital Sky Survey photometry, and spectroscopy where available, and present identifications of the 25 FIR sources which reach down to ~150mJy in all three ISOPHOT bands. Identifications are done by means of full spectral energy density fitting to all sources in the FIR error circle areas.
- ID:
- ivo://CDS.VizieR/J/A+A/418/33
- Title:
- RI photometry of C stars in NGC 147
- Short Name:
- J/A+A/418/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have imaged a 42'x28' field centered on the spheroidal galaxy NGC 147 to study its AGB population and determine the main structural properties of this M31 companion. This field was observed through two broadband (R and I) and two narrowband (CN and TiO) filters, following the standard approach of our systematic survey of C stars in nearby galaxies. We identified 288 C stars in NGC 147. The average I-magnitude of such sample of C stars is <I>=20.31 with {sigma}=0.40. If we adopt a distance modulus {mu}0=24.39, derived from the luminosity of both the tip of the red giant branch (TRGB) and the horizontal branch (HB) by Han et al. (1997, Cat. <J/AJ/113/1001>, we conclude that the average absolute I-magnitude of C stars is <M_I_>=-4.39, thus slightly under luminous with respect to what was found for other galaxies in our survey.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A20
- Title:
- r' magnitudes and sizes of Oph cluster galaxies
- Short Name:
- J/A+A/613/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ophiuchus is one of the most massive clusters known, but due to its low Galactic latitude its optical properties remain poorly known. We investigate the optical properties of Ophiuchus to obtain clues on the formation epoch of this cluster, and compare them to those of the Coma cluster, which is comparable in mass to Ophiuchus but much more dynamically disturbed. Based on a deep image of the Ophiuchus cluster in the r' band obtained at the Canada France Hawaii Telescope with the MegaCam camera, we have applied an iterative process to subtract the contribution of the numerous stars that, due to the low Galactic latitude of the cluster, pollute the image, and have obtained a photometric catalogue of 2818 galaxies fully complete at r'=20.5mag and still 91% complete at r'=21.5mag. We use this catalogue to derive the cluster Galaxy Luminosity Function (GLF) for the overall image and for a region (hereafter the "rectangle" region) covering exactly the same physical size as the region in which the GLF of the Coma cluster was previously studied. We then compute density maps based on an adaptive kernel technique, for different magnitude limits, and define three circular regions covering 0.08, 0.08, and 0.06 deg^2^, respectively, centred on the cluster (C), on northwest (NW) of the cluster, and southeast (SE) of the cluster, in which we compute the GLFs. The GLF fits are much better when a Gaussian is added to the usual Schechter function, to account for the excess of very bright galaxies. Compared to Coma, Ophiuchus shows a strong excess of bright galaxies. The properties of the two nearby very massive clusters Ophiuchus and Coma are quite comparable, though they seem embedded in different large-scale environments. Our interpretation is that Ophiuchus was built up long ago, as confirmed by its relaxed state (see paper I, Durret et al., 2015, Cat. J/A+A/583/A124) while Coma is still in the process of forming.