- ID:
- ivo://CDS.VizieR/J/A+A/405/99
- Title:
- LSB galaxies in near-infrared. I.
- Short Name:
- J/A+A/405/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of about 3800 Low Surface Brightness (LSB) galaxies was selected using the all-sky near-infrared (J, H and Ks-band) 2MASS survey. The selected objects have a mean central surface brightness within a 5" radius around their centre fainter than 18mag/arcsec^2^ in the Ks band, making them the lowest surface brightness galaxies detected by 2MASS. A description is given of the relevant properties of the 2MASS survey and the LSB galaxy selection procedure, as well as of basic photometric properties of the selected objects. The latter properties are compared to those of other samples of galaxies, of both LSBs and "classical'' high surface brightness (HSB) objects, which were selected in the optical. The 2MASS LSBs have a B_Tc_-K_T_ colour colour which is on average 0.9mag bluer than that of HSBs from the NGC. The 2MASS sample does not appear to contain a significant population of red objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/408/67
- Title:
- LSB galaxies in near-infrared. II.
- Short Name:
- J/A+A/408/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A total of 367 Low Surface Brightness galaxies detected in the 2MASS all-sky near-infrared survey have been observed in the 21 cm H I line using the Arecibo telescope. All have a Ks-band mean central surface brightness, measured within a 5" radius, fainter than 18mag/arcsec^2^. We present global H I line parameters for the 107 clearly detected objects and the 21 marginal detections, as well as upper limits for the undetected objects. The 107 clear detections comprise 15 previously uncatalogued objects and 36 with a PGC entry only.
- ID:
- ivo://CDS.VizieR/J/A+A/408/465
- Title:
- LSB galaxies in near-infrared. III.
- Short Name:
- J/A+A/408/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A total of 334 Low Surface Brightness galaxies detected in the 2MASS all-sky near-infrared survey have been observed in the 21 cm H I line using the Nancay telescope. All have a Ks-band mean central surface brightness, measured within a 5" radius, fainter than 18mag/arcsec^2^ and a Ks-band isophotal radius at the 20mag/arcsec^2^ level larger than 20". We present global H I line parameters for the 171 clearly detected objects and the 23 marginal detections, as well as upper limits for the undetected objects. The 171 clear detections comprise 50 previously uncatalogued objects and 41 objects with a PGC entry only.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A145
- Title:
- L9-T3.5 brown dwarfs light curves
- Short Name:
- J/A+A/629/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Brown dwarfs in the spectral range L9-T3.5, within the so called L/T transition, have been shown to be variable at higher amplitudes and with greater frequency than other field dwarfs. This strong variability allows for the probing of their atmospheric structure in 3D through multi-wavelength observations for studying the underlying physical mechanisms responsible for the variability. The few known strongly variable dwarfs in this range have been extensively studied. Now, more variables such as these need to be discovered and studied to better constrain atmospheric models. This is also critical to better understand giant exoplanets and to shed light on a number of possible correlations between brown dwarf characteristics and variability. Previous studies suggest an occurrence rate for strong variability (peak-to-peak amplitudes >2%) of up to 39% among brown dwarfs within the L/T transition. In this work, we aim to discover new strong variables in this spectral range by targeting ten previously unsurveyed brown dwarfs. We used the NOTCam at the Nordic Optical Telescope to observe 11 targets, with spectral types ranging from L9.5 to T3.5, in the J-band during October 2017 and September 2018. Using differential aperture photometry, we then analysed the light curves for significant variability using Lomb-Scargle periodogram algorithms and least squares fitting. We report first discoveries of strong and significant variability in four out of the ten targets (false alarm probability <0.1%), measuring peak-to-peak amplitudes up to 10.7+/-0.4% in J for the T1 dwarf 2MASS J22153705+2110554, for which we observe significant light curve evolution between the 2017 and 2018 epochs. We also report a marginally significant detection of strong variability, and confirm that the well known 2MASS J01365662+0933473 is still strongly variable three years after the last reported epoch. Finally, we present an extensive multi-epoch catalogue of strong variables reported in the literature and discuss possible correlations that are identifiable from the catalogue. We significantly add to the number of known strong variables, and through Poisson statistics infer an occurrence rate for strong variability among L9-T3.5 brown dwarfs of 40^+32^_19_%, which is in agreement with previous estimates. The new variables identified in this work are also excellently suited for extensive multi-wavelength observations dedicated to probing the 3D structure of brown dwarf atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/118
- Title:
- L/T transition dwarfs search with PS1 & WISE. II.
- Short Name:
- J/ApJ/814/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of brown dwarfs from L to T spectral types is one of the least understood aspects of the ultracool population, partly for lack of a large, well-defined, and well-characterized sample in the L/T transition. To improve the existing census, we have searched ~28000deg^2^ using the Pan-STARRS1 and Wide-field Infrared Survey Explorer surveys for L/T transition dwarfs within 25pc. We present 130 ultracool dwarf discoveries with estimated distances ~9-130pc, including 21 that were independently discovered by other authors and 3 that were previously identified as photometric candidates. Seventy-nine of our objects have near-IR spectral types of L6-T4.5, the most L/T transition dwarfs from any search to date, and we have increased the census of L9-T1.5 objects within 25pc by over 50%. The color distribution of our discoveries provides further evidence for the "L/T gap", a deficit of objects with (J-K)_MKO_~0.0-0.5mag in the L/T transition, and thus reinforces the idea that the transition from cloudy to clear photospheres occurs rapidly. Among our discoveries are 31 candidate binaries based on their low-resolution spectral features. Two of these candidates are common proper motion companions to nearby main sequence stars; if confirmed as binaries, these would be rare benchmark systems with the potential to stringently test ultracool evolutionary models. Our search also serendipitously identified 23 late-M and L dwarfs with spectroscopic signs of low gravity implying youth, including 10 with vl-g or int-g gravity classifications and another 13 with indications of low gravity whose spectral types or modest spectral signal-to-noise ratio do not allow us to assign formal classifications. Finally, we identify 10 candidate members of nearby young moving groups (YMG) with spectral types L7-T4.5, including three showing spectroscopic signs of low gravity. If confirmed, any of these would be among the coolest known YMG members and would help to determine the effective temperature at which young brown dwarfs cross the L/T transition.
- ID:
- ivo://CDS.VizieR/J/ApJ/604/521
- Title:
- Luminosities and masses of galaxies out to z~3
- Short Name:
- J/ApJ/604/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity-size and mass-size distributions of galaxies out to z~3 are presented. We use very deep near-infrared images of the Hubble Deep Field-South in the J_s_, H, and K_s_ bands, taken as part of FIRES at the VLT, to follow the evolution of the optical rest-frame sizes of galaxies. For a total of 168 galaxies with K_s,AB_ <=23.5, we find that the rest-frame V-band sizes r_e,V_ of luminous galaxies (<L_V_>~2x10^10^h^-2^L_{sun}_) at 2<z<3 are 3 times smaller than for equally luminous galaxies today. In contrast, the mass-size relation has evolved relatively little: the size at mass <M_*_>~2x10^10^h^-2^M_{sun}_ has changed by 20% (+/-20%) since z~2.5. Both results can be reconciled by the fact that the stellar M/L ratio is lower in the luminous high-z galaxies than in nearby ones because they have young stellar populations. The lower incidence of large galaxies at z~3 seems to reflect the rarity of galaxies with high stellar mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/45
- Title:
- Luminosity and redshift of galaxies from WISE/SDSS
- Short Name:
- J/ApJ/788/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 {mu}m luminosity functions (LFs) at 0.006<=z<=0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog (Cat. II/311) with Sloan Digital Sky Survey (SDSS, Cat. II/294) spectroscopic data, we selected 223982 galaxies at 12 {mu}m and 25721 galaxies at 22 {mu}m for spectroscopic classification. We then identified 16355 AGNs at 12 {mu}m and 4683 AGNs at 22 {mu}m by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z<=0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
- ID:
- ivo://CDS.VizieR/J/AJ/133/439
- Title:
- Luminosity function of M7-L8 ultracool dwarfs
- Short Name:
- J/AJ/133/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 20pc, volume-limited sample of M7-L8 dwarfs created through spectroscopic follow-up of sources selected from the Two Micron All Sky Survey Second Incremental Release Point Source Catalog. In this paper we present optical spectroscopy of 198 candidate nearby ultracool dwarfs, including 12 late-M and L dwarfs likely to be within 20pc of the Sun and 94 more distant late-type dwarfs. We have also identified five ultracool dwarfs with spectral signatures of low gravity. Combining these data with previous results, we define a sample of 99 ultracool dwarfs in 91 systems within 20pc. These are used to estimate the J- and K-band luminosity functions for dwarfs with optical spectral types between M7 and L8 (10.5<M_J_<15, 9.5<M_Ks_<13). We find a space density of 4.9x10^-3^/pc^3^ for late-M dwarfs (M7-M9.5) and a lower limit of 3.8x10^-3^/pc^3^ for L dwarfs.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/447/89
- Title:
- Luminous AGB stars in nearby galaxies
- Short Name:
- J/A+A/447/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study focuses on very luminous (M_bol_<-6.0mag) AGB stars with J-Ks>1.5mag and H-Ks>0.4mag in the LMC, SMC, M 31, and M 33 from 2MASS data.
