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1451. Low X-ray luminosity galaxy clusters
ID:
ivo://CDS.VizieR/J/MNRAS/437/2607
Title:
Low X-ray luminosity galaxy clusters
Short Name:
J/MNRAS/437/2607
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is the second of a series of papers on low X-ray luminosity galaxy clusters, in which we present the r', g' and i' photometry obtained with Gemini Multi-Object Spectrograph IMAGE at Gemini North and South telescopes for seven systems in the redshift range of 0.18 to 0.70. Optical magnitudes, colours and morphological parameters, namely, concentration index, ellipticity and visual morphological classification, are also given. At lower redshifts, the presence of a well-defined red cluster sequence extending by more than 4mag showed that these intermediate-mass clusters had reached a relaxed stage. This was confirmed by the small fraction of blue galaxy members observed in the central regions of ~0.75Mpc. In contrast, galaxy clusters at higher redshifts had a less important red cluster sequence. We also found that the galaxy radial density profiles in these clusters were well fitted by a single power law. At 0.18<z<0.70, we observed an increasing fraction of blue galaxies and a decreasing fraction of lenticulars, with the early-type fraction remaining almost constant. Overall, the results of these intermediate-mass clusters are in agreement with those for high-mass clusters.
1452. LRG catalog
ID:
ivo://CDS.VizieR/J/MNRAS/380/1608
Title:
LRG catalog
Short Name:
J/MNRAS/380/1608
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work I discuss the necessary steps for deriving photometric redshifts for luminous red galaxies (LRGs) and galaxy clusters through simple empirical methods. The data used are from the Sloan Digital Sky Survey (SDSS). I show that with three bands only (gri) it is possible to achieve results as accurate as the ones obtained by other techniques, generally based on more filters. In particular, the use of the (g-i) colour helps improving the final redshifts (especially for clusters), as this colour monotonically increases up to z~0.8. For the LRGs I generate a catalogue of ~1.5 million objects at z<0.70. The accuracy of this catalogue is sigma=0.027 for z<=0.55 and sigma=0.049 for 0.55<z<=0.70. The photometric redshift technique employed for clusters is independent of a cluster selection algorithm. Thus, it can be applied to systems selected by any method or wavelength, as long as the proper optical photometry is available. When comparing the redshift listed in literature to the photometric estimate, the accuracy achieved for clusters is sigma=0.024 for z<=0.30 and sigma=0.037 for 0.30<z<=0.55. However, when considering the spectroscopic redshift as the mean value of SDSS galaxies on each cluster region, the accuracy is at the same level as found by other authors: sigma=0.011 for z<=0.30 and sigma=0.016 for 0.30<z<=0.55. The photometric redshift relation derived here is applied to thousands of cluster candidates selected elsewhere. I have also used galaxy photometric redshifts available in SDSS to identify groups in redshift space and then compare the redshift peak of the nearest group to each cluster redshift. This procedure provides an alternative approach for cluster selection, especially at high redshifts, as the cluster red sequence may be poorly defined.
1453. LSB galaxies rotation curves
ID:
ivo://CDS.VizieR/J/A+A/385/816
Title:
LSB galaxies rotation curves
Short Name:
J/A+A/385/816
Date:
21 Oct 2021
Publisher:
CDS
Description:
File rawcurve contains the raw rotation curves of the low surface brightness galaxies. These data are not corrected for inclination. File procurve contains the processed rotation curves that can be directly used for mass modelling.
1454. LSBG HI and optical properties
ID:
ivo://CDS.VizieR/J/MNRAS/476/4488
Title:
LSBG HI and optical properties
Short Name:
J/MNRAS/476/4488
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the HI and optical properties of nearby (z<=0.1) Low Surface Brightness galaxies (LSBGs). We started with a literature sample of ~900 LSBGs and divided them into three morphological classes: spirals, irregulars, and dwarfs. Of these, we could use ~490 LSBGs to study their HI and stellar masses, colours, and colour-magnitude diagrams, and local environment, compare them with normal, High Surface Brightness (HSB) galaxies and determine the differences between the three morphological classes. We found that LSB and HSB galaxies span a similar range in HI and stellar masses, and have a similar M_HI_/M_{star}_-M_{star}_ relationship. Among the LSBGs, as expected, the spirals have the highest average HI and stellar masses, both of about 10^9.8^M_{sun}_. The LSGBs' (g-r) integrated colour is nearly constant as function of HI mass for all classes. In the colour-magnitude diagram, the spirals are spread over the red and blue regions whereas the irregulars and dwarfs are confined to the blue region. The spirals also exhibit a steeper slope in the M_HI_/M_{star}_-M_{star}_ plane. Within their local environment, we confirmed that LSBGs are more isolated than HSB galaxies, and LSB spirals more isolated than irregulars and dwarfs. Kolmogorov-Smirnov statistical tests on the HI mass, stellar mass, and number of neighbours indicate that the spirals are a statistically different population from the dwarfs and irregulars. This suggests that the spirals may have different formation and HI evolution than the dwarfs and irregulars.
1455. LSBG in Arecibo HI Strip Survey
ID:
ivo://CDS.VizieR/J/A+A/458/341
Title:
LSBG in Arecibo HI Strip Survey
Short Name:
J/A+A/458/341
Date:
21 Oct 2021
Publisher:
CDS
Description:
In order to estimate the contribution of low surface brightness (LSB) galaxies to the local (z<=0.1) galaxy number density, we performed an optical search for LSB candidates in a 15.5{deg}^2^ part of the region covered by the 65{deg}^2^ blind Arecibo HI Strip Survey (AHISS)
1456. LSPM-North proper-motion catalog nearby stars
ID:
ivo://CDS.VizieR/J/AJ/130/1680
Title:
LSPM-North proper-motion catalog nearby stars
Short Name:
J/AJ/130/1680
Date:
21 Oct 2021
Publisher:
CDS
Description:
A list of 4131 dwarfs, subgiants, and giants located or suspected to be located within 33pc of the Sun is presented. All the stars are drawn from the new Lepine Shara Proper Motion (LSPM)-North catalog (Cat. <I/298>) of 61,976 stars with annual proper motions larger than 0.15"/yr. Trigonometric parallax measurements are found in the literature for 1676 of the stars in the sample; photometric and spectroscopic distance moduli are found for another 783 objects. The remaining 1672 objects are reported here as nearby star candidates for the first time. Photometric distance moduli are calculated for the new stars based on the (M_V_, V-J) relationship, calibrated with the subsample of stars that have trigonometric parallaxes. The list of new candidates includes 539 stars that are suspected to be within 25pc of the Sun, including 63 stars estimated to be within only 15pc.
1457. Luminosity functions of tidal disruption flares
ID:
ivo://CDS.VizieR/J/ApJ/852/72
Title:
Luminosity functions of tidal disruption flares
Short Name:
J/ApJ/852/72
Date:
21 Oct 2021
Publisher:
CDS
Description:
The tidal disruption of a star by a massive black hole is expected to yield a luminous flare of thermal emission. About two dozen of these stellar tidal disruption flares (TDFs) may have been detected in optical transient surveys. However, explaining the observed properties of these events within the tidal disruption paradigm is not yet possible. This theoretical ambiguity has led some authors to suggest that optical TDFs are due to a different process, such as a nuclear supernova or accretion disk instabilities. Here we present a test of a fundamental prediction of the tidal disruption event scenario: a suppression of the flare rate due to the direct capture of stars by the black hole. Using a recently compiled sample of candidate TDFs with black hole mass measurements, plus a careful treatment of selection effects in this flux-limited sample, we confirm that the dearth of observed TDFs from high-mass black holes is statistically significant. All the TDF impostor models we consider fail to explain the observed mass function; the only scenario that fits the data is a suppression of the rate due to direct captures. We find that this suppression can explain the low volumetric rate of the luminous TDF candidate ASASSN-15lh, thus supporting the hypothesis that this flare belongs to the TDF family. Our work is the first to present the optical TDF luminosity function. A steep power law is required to explain the observed rest-frame g-band luminosity, dN/dL_g_{propto}L_g_^-2.5^. The mean event rate of the flares in our sample is ~1x10^-4^galaxy^-1^/yr, consistent with the theoretically expected tidal disruption rate.
1458. Luminous AGNs and early-type SDSS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/804/34
Title:
Luminous AGNs and early-type SDSS galaxies
Short Name:
J/ApJ/804/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
It is not yet clear what triggers the activity of active galactic nuclei (AGNs), but galaxy merging has been suspected to be one of the main mechanisms fueling the activity. Using deep optical images taken at various ground-based telescopes, we investigate the fraction of galaxy mergers in 39 luminous AGNs (M_R_<~-22.6mag) at z<=0.3 (a median redshift of 0.155), for which the host galaxies are generally considered as early-type galaxies. Through visual inspection of the images, we find that 17 of 39 AGN host galaxies (43.6%) show evidence for current or past mergers like tidal tails, shells, and disturbed morphology. In order to see if this fraction is abnormally high, we also examined the merging fraction of normal early-type galaxies in the Sloan Digital Sky Survey (SDSS) Stripe 82 data (a median redshift of 0.04), of which the surface-brightness limit is comparable to our imaging data. To correct for the effects related to the redshift difference of the two samples, we performed an image simulation by putting a bright point source as an artificial AGN in the images of SDSS early-type galaxies and placing them onto the redshifts of AGNs. The merging fraction in this realistic sample of simulated AGNs is only ~5-15% (1/4 to 1/8 of that of real AGNs). Our result strongly suggests that luminous AGN activity is associated with galaxy merging.
1459. Luminous and variable stars in NGC 2403 and M81
ID:
ivo://CDS.VizieR/J/AJ/157/22
Title:
Luminous and variable stars in NGC 2403 and M81
Short Name:
J/AJ/157/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high-luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars that were previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respective galaxies. We also present the HR Diagrams for the two "SN impostors", V37 (SN2002kg) and V12 (SN1954J) in NGC 2403 and the stars in their immediate environments.
1460. Luminous cool supergiants in Magellanic Clouds
ID:
ivo://CDS.VizieR/J/MNRAS/478/3138
Title:
Luminous cool supergiants in Magellanic Clouds
Short Name:
J/MNRAS/478/3138
Date:
21 Oct 2021
Publisher:
CDS
Description:
The empirical upper luminosity boundary L_max_ of cool supergiants, often referred to as the Humphreys-Davidson limit, is thought to encode information on the general mass-loss behaviour of massive stars. Further, it delineates the boundary at which single stars will end their lives stripped of their hydrogen-rich envelope, which in turn is a key factor in the relative rates of Type-II to Type-Ibc supernovae from single star channels. In this paper we have revisited the issue of L_max_ by studying the luminosity distributions of cool supergiants (SGs) in the Large and Small Magellanic Clouds (LMC/SMC). We assemble highly-complete samples of cool SGs in each galaxy, and determine their spectral energy distributions from the optical to the mid-infrared using modern multi-wavelength survey data. We show that in both cases L_max_ appears to be lower than previously quoted, and is in the region of logL/L_{sun}_=5.5. There is no evidence for L_max_ being higher in the SMC than in the LMC, as would be expected if metallicity-dependent winds were the dominant factor in the stripping of stellar envelopes. We also show that L_max_ aligns with the lowest luminosity of single nitrogen-rich Wolf-Rayet stars, indicating of a change in evolutionary sequence for stars above a critical mass. From population synthesis analysis we show that the Geneva evolutionary models greatly over-predict the numbers of cool SGs in the SMC. We also argue that the trend of earlier average spectral types of cool SGs in lower metallicity environments represents a genuine shift to hotter temperatures. Finally, we use our new bolometric luminosity measurements to provide updated bolometric corrections for cool supergiants.