Search

Start Over Validation Level 2
23131. 9.7um silicate features in AGNs
ID:
ivo://CDS.VizieR/J/ApJ/653/127
Title:
9.7um silicate features in AGNs
Short Name:
J/ApJ/653/127
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe observations of 9.7um silicate features in 97 AGNs, exhibiting a wide range of AGN types and of X-ray extinction toward the central nuclei. We find that the strength of the silicate feature correlates with the HI column density estimated from fitting the X-ray data, such that low HI columns correspond to silicate emission, while high columns correspond to silicate absorption. The behavior is generally consistent with unification models in which the large diversity in AGN properties is caused by viewing-angle-dependent obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars follow roughly the correlation between HI columns and the strength of the silicate feature defined by Seyfert galaxies. The agreement among AGN types suggests a high-level unification with similar characteristics for the structure of the obscuring material. We demonstrate the implications for unification models qualitatively with a conceptual disk model. The model includes an inner accretion disk (<0.1pc in radius), a middle disk (0.110pc in radius) with a dense diffuse component and with embedded denser clouds, and an outer clumpy disk (10-300pc in radius).
23132. 8.1um SiO spectra of cool evolved stars
ID:
ivo://CDS.VizieR/J/A+A/561/A47
Title:
8.1um SiO spectra of cool evolved stars
Short Name:
J/A+A/561/A47
Date:
21 Oct 2021
Publisher:
CDS
Description:
The mass-loss mechanism in red giants and red supergiants is not yet understood well. The SiO fundamental lines near 8 m are potentially useful for probing the outer atmosphere, which is essential for clarifying the mass-loss mechanism. However, these lines have been little explored until now. We present high spectral resolution spectroscopic observations of the SiO fundamental lines near 8.1um in 16 bright red giants and red supergiants. Our sample consists of seven normal (i.e., non-Mira) K-M giants (from K1.5 to M6.5), three Mira stars, three optically bright red supergiants, two dusty red supergiants, and the enigmatic object GCIRS3 near the Galactic center.
23133. 0.8-2.5um spectra of 2 red quasars
ID:
ivo://CDS.VizieR/J/A+A/610/A31
Title:
0.8-2.5um spectra of 2 red quasars
Short Name:
J/A+A/610/A31
Date:
21 Oct 2021
Publisher:
CDS
Description:
Red quasars are very red in the optical through near-infrared (NIR) wavelengths, which is possibly due to dust extinction in their host galaxies as expected in a scenario in which red quasars are an intermediate population between merger-driven star-forming galaxies and unobscured type 1 quasars. However, alternative mechanisms also exist to explain their red colors: (i) an intrinsically red continuum; (ii) an unusual high covering factor of the hot dust component, that is, CF_HD_=L_HD_/L_bol_, where the L_HD_ is the luminosity from the hot dust component and the L_bol_ is the bolometric luminosity; and (iii) a moderate viewing angle. In order to investigate why red quasars are red, we studied optical and NIR spectra of 20 red quasars at z~0.3 and 0.7, where the usage of the NIR spectra allowed us to look into red quasar properties in ways that are little affected by dust extinction. The Paschen to Balmer line ratios were derived for 13 red quasars and the values were found to be ~10 times higher than unobscured type 1 quasars, suggesting a heavy dust extinction with A_V_>2.5mag. Furthermore, the Paschen to Balmer line ratios of red quasars are difficult to explain with plausible physical conditions without adopting the concept of the dust extinction. The CF_HD_ of red quasars are similar to, or marginally higher than, those of unobscured type 1 quasars. The Eddington ratios, computed for 19 out of 20 red quasars, are higher than those of unobscured type 1 quasars (by factors of 3-5), and hence the moderate viewing angle scenario is disfavored. Consequently, these results strongly suggest the dust extinction that is connected to an enhanced nuclear activity as the origin of the red color of red quasars, which is consistent with the merger-driven quasar evolution scenario.
23134. 1.1-2.4um spectra of 7 young M and L dwarfs
ID:
ivo://CDS.VizieR/J/A+A/564/A55
Title:
1.1-2.4um spectra of 7 young M and L dwarfs
Short Name:
J/A+A/564/A55
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gravity modifies the spectral features of young brown dwarfs (BDs). A proper characterization of these objects is crucial for the identification of the least massive and latest-type objects in star-forming regions, and to explain the origin(s) of the peculiar spectrophotometric properties of young directly imaged extrasolar planets and BD companions. We obtained medium-resolution (R~1500-1700) near-infrared (1.1-2.5um) spectra of seven young M9.5-L3 dwarfs classified at optical wavelengths. We aim to empirically confirm the low surface gravity of the objects in the near-infrared. We also test whether self-consistent atmospheric models correctly represent the formation and the settling of dust clouds in the atmosphere of young late-M and L dwarfs. We used the Infrared Spectrometer And Array Camera (ISAAC) at the Very Large Telescope (VLT) to obtain the spectra of the targets. We compared the spectra to those of mature and young BDs, and to young late-type companions to nearby stars with known ages, to identify and study gravity-sensitive features. We computed spectral indices weakly sensitive to the surface gravity to derive near-infrared spectral types. Finally, we found the best fit between each spectrum and synthetic spectra from the BT-Settl 2010 and 2013 atmospheric models. Using the best fit, we derived the atmospheric parameters of the objects and identified which spectral characteristics the models do not reproduce.
23135. 3.6um surface brightness from S4G
ID:
ivo://CDS.VizieR/J/ApJ/772/135
Title:
3.6um surface brightness from S4G
Short Name:
J/ApJ/772/135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the m=1 distortions (lopsidedness) in the stellar components of 167 nearby galaxies that span a wide range of morphologies and luminosities. We confirm the previous findings of (1) a high incidence of lopsidedness in the stellar distributions, (2) increasing lopsidedness as a function of radius out to at least 3.5 exponential scale lengths, and (3) greater lopsidedness, over these radii, for galaxies of later type and lower surface brightness. Additionally, the magnitude of the lopsidedness (1) correlates with the character of the spiral arms (stronger arm patterns occur in galaxies with less lopsidedness), (2) is not correlated with the presence or absence of a bar, or the strength of the bar when one is present, (3) is inversely correlated to the stellar mass fraction, f_*_, within one radial scale length, and (4) correlates directly with f_*_ measured within the radial range over which we measure lopsidedness. We interpret these findings to mean that lopsidedness is a generic feature of galaxies and does not, generally, depend on a rare event, such as a direct accretion of a satellite galaxy onto the disk of the parent galaxy. While lopsidedness may be caused by several phenomena, moderate lopsidedness (<A_1_>_i_+<A_1_>_o_)/2<0.3) is likely to reflect halo asymmetries to which the disk responds or a gravitationally self-generated mode. We hypothesize that the magnitude of the stellar response depends both on how centrally concentrated the stars are with respect to the dark matter and whether there are enough stars in the region of the lopsidedness that self-gravity is dynamically important.
23136. 14.3um survey in the Lockman Hole
ID:
ivo://CDS.VizieR/J/A+A/427/23
Title:
14.3um survey in the Lockman Hole
Short Name:
J/A+A/427/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the image and catalogue of the 14.3{mu}m hallow survey of 0.55 square degrees in the region of the Lockman Hole (10h 52m 03s, +57{deg} 21' 46", J2000). The data have been analyzed with the recent algorithm by Lari et al. (2001, Cat. <J/MNRAS/325/1173>) conceived to exploit ISO data in an optimal way, especially in the case of shallow surveys with low redundancy. Photometry has been accurately evaluated through extensive simulations and also the absolute calibration has been checked using a set of 21 stars detected at 14.3{mu}m, optical, and near-IR bands.
23137. 3.6um, 4.5um, B and V light curves of NGC 6418
ID:
ivo://CDS.VizieR/J/ApJ/801/127
Title:
3.6um, 4.5um, B and V light curves of NGC 6418
Short Name:
J/ApJ/801/127
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a 15 month campaign of high-cadence (~3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4.5{mu}m flux variations lag behind those of the optical continuum by 37.2_-2.2_^+2.4^-days and 47.1_-3.1_^+3.1^-days, respectively. We report a cross-correlation time lag between the 4.5 and 3.6{mu}m flux of 13.9_-0.1_^+0.5^ days. The lags indicate that the dust emitting at 3.6 and 4.5{mu}m is located at a distance ~1-light-month (~0.03pc) from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800K, but smaller by a factor of ~2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGNs. The 3.6 and 4.5{mu}m reverberation radii fall above the K-band {tau}{propto}L^0.5^ size-luminosity relationship by factors <~2.8 and <~3.4, respectively, while the 4.5{mu}m reverberation radius is only 27% larger than the 3.6{mu}m radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range.
23138. UNAM-KIAS catalog of isolated galaxies
ID:
ivo://CDS.VizieR/J/AJ/139/2525
Title:
UNAM-KIAS catalog of isolated galaxies
Short Name:
J/AJ/139/2525
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new catalog of isolated galaxies from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) is presented. A total of 1520 isolated galaxies were found in 1.4sr of sky. The selection criteria in this UNAM-KIAS catalog are a variation on the criteria developed by Karachentseva, including full redshift information. Through an image processing pipeline that takes advantage of the high-resolution (~0.4"/pix) and high dynamic range of the SDSS images, a uniform g-band morphological classification for all these galaxies is presented.
23139. Unbiased census of AGN in 2MASS
ID:
ivo://CDS.VizieR/J/AJ/127/646
Title:
Unbiased census of AGN in 2MASS
Short Name:
J/AJ/127/646
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an unbiased near-IR-selected AGN sample, covering 12.56deg^2^ down to Ks~15.5, selected from the Two Micron All Sky Survey (2MASS). Our only selection effect is a moderate color cut (J-Ks>1.2) designed to reduce contamination from Galactic stars. We observed both pointlike and extended sources.
23140. Unbiased sample of CSS and GPS
ID:
ivo://CDS.VizieR/J/MNRAS/416/1135
Title:
Unbiased sample of CSS and GPS
Short Name:
J/MNRAS/416/1135
Date:
21 Oct 2021
Publisher:
CDS
Description:
Compact Steep Spectrum (CSS) and Gigahertz Peaked Spectrum (GPS) sources are classes of compact, powerful, extragalactic objects. These sources are thought to be the earliest stages in the evolution of radio galaxies, capturing the ignition (or, in some cases, re-ignition) of the active galactic nucleus. As well as serving as probes of the early stages of large-scale radio sources, these sources are good, stable, amplitude calibrators for radio telescopes. We present an unbiased flux density limited (>1.5Jy at 2.7GHz) catalogue of these objects in the Southern hemisphere, including tabulated data, radio spectra, and where available, optical images and measurements. The catalogue contains 26 sources, consisting of two new candidates and 15 known CSS sources, and nine known GPS sources. We present new Australia Telescope Compact Array (ATCA) data on 10 of these 26 sources, and data on a further 42 sources which were excluded from our final sample. This bright sample will serve as a reference sample for comparison with subsequent faint (mJy level) samples of CSS and GPS candidates currently being compiled.

Limit your search

more »

more »

more »

more »

more »

more »

more »

more »