- ID:
- ivo://CDS.VizieR/J/ApJS/219/18
- Title:
- LIRAS: LoCuSS IR AGN survey
- Short Name:
- J/ApJS/219/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 290 24{mu}m-selected active galactic nuclei (AGNs) mostly at z~0.3-2.5, within 5.2{deg}^2^ distributed as 25'x25' fields around each of 30 galaxy clusters in the Local Cluster Substructure Survey. The sample is nearly complete to 1mJy at 24{mu}m, and has a rich multiwavelength set of ancillary data; 162 are detected by Herschel. We use spectral templates for AGNs, stellar populations, and infrared (IR) emission by star-forming galaxies to decompose the spectral energy distributions (SEDs) of these AGNs and their host galaxies, and estimate their star formation rates, AGN luminosities, and host galaxy stellar masses. The set of templates is relatively simple: a standard Type-1 quasar template; another for the photospheric output of the stellar population; and a far-infrared star-forming template. For the Type-2 AGN SEDs, we substitute templates including internal obscuration, and some Type-1 objects require a warm component (T>~50K). The individually Herschel-detected Type-1 AGNs and a subset of 17 Type-2 AGNs typically have luminosities >10^45^erg/s, and supermassive black holes of ~3x10^8^M_{sun}_ emitting at ~10% of the Eddington rate. We find them in about twice the numbers of AGNs identified in SDSS data in the same fields, i.e., they represent typical high-luminosity AGNs, not an IR-selected minority. These AGNs and their host galaxies are studied further in an accompanying paper.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/420/945
- Title:
- L1551 ISOCAM observations
- Short Name:
- J/A+A/420/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a deep mid-IR ISOCAM survey of the L1551 dark molecular cloud are presented. The aim of this survey is a search for new YSO (Young Stellar Object) candidates, using two broad-band filters centred at 6.7 and 14.3{mu}m. Although two regions close to the centre of L1551 had to be avoided due to saturation problems, 96 sources were detected in total (76 sources at 6.7{mu}m and 44 sources at 14.3{mu}m). Using the 24 sources detected in both filters, 14 were found to have intrinsic mid-IR excess at 14.3{mu}m and were therefore classified as YSO candidates. Using additional observations in B, V, I, J, H and K obtained from the ground, most candidates detected at these wavelengths were confirmed to have mid-IR excess at 6.7{mu}m as well, and three additional YSO candidates were found.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A36
- Title:
- Lithium abundances of bulge RGB stars
- Short Name:
- J/A+A/538/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A small number of K-type giants on the red giant branch (RGB) is known to be very rich in lithium (Li). This fact is not accounted for by standard stellar evolution theory. The exact phase and mechanism of Li enrichment is still a matter of debate. Our goal is to probe the abundance of Li along the RGB, from its base to the tip, to confine Li-rich phases that are supposed to occur on the RGB. For this end, we obtained medium-resolution spectra with the FLAMES spectrograph at the VLT in GIRAFFE mode for a large sample of 401 low-mass RGB stars located in the Galactic bulge. The Li abundance was measured in the stars with a detectable Li 670.8 nm line by means of spectral synthesis with COMARCS model atmospheres. A new 2MASS J-K-Teff calibration from COMARCS models is presented in the Appendix. Thirty-one stars with a detectable Li line were identified, three of which are Li-rich according to the usual criterion (log{epsilon}_Li_>1.5). The stars are distributed all along the RGB, not concentrated in any particular phase of the red giant evolution (e.g. the luminosity bump or the red clump). The three Li-rich stars are clearly brighter than the luminosity bump and red clump, and do not show any signs of enhanced mass loss. We conclude that the Li enrichment mechanism cannot be restricted to a clearly defined phase of the RGB evolution of low-mass stars (M~1M_{sun}_), contrary to earlier suggestions from disk field stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/1295
- Title:
- Lithium test implications for brown dwarfs
- Short Name:
- J/ApJ/689/1295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a large sample of optical spectra of late-type dwarfs, we identify a subset of late-M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young. From a combined sample of 303 field L dwarfs, we find observationally that 7.6+/-1.6% are younger than 100Myr. This percentage is in agreement with theoretical predictions once observing biases are taken into account. We find that these young L dwarfs tend to fall in the southern hemisphere (DEC<0{deg}) and may be previously unrecognized, low-mass members of nearby, young associations like Tucana-Horologium, TW Hydrae, {beta} Pictoris, and AB Doradus. We use a homogeneously observed sample of ~150 optical spectra to examine lithium strength as a function of L/T spectral type and further corroborate the trends noted by Kirkpatrick and coworkers. We use our low-gravity spectra to investigate lithium strength as a function of age. The data weakly suggest that for early- to mid-L dwarfs the line strength reaches a maximum for a fewx100Myr, whereas for much older (few Gyr) and much younger (<100Myr) L dwarfs the line is weaker or undetectable.
- ID:
- ivo://CDS.VizieR/J/AJ/128/1233
- Title:
- LkH{alpha} 101 and the young cluster in NGC 1579
- Short Name:
- J/AJ/128/1233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central region of the dark cloud L1482 is illuminated by LkH{alpha} 101, a heavily reddened (A_V_~10mag) high-luminosity (>=8x10^3^L_Sun_) star having an unusual emission-line spectrum plus a featureless continuum. About 35 much fainter (mostly between R=16 and >21) H{alpha} emitters have been found in the cloud. Their color-magnitude distribution suggests a median age of about 0.5Myr, with considerable dispersion. There are also at least five bright B-type stars in the cloud, presumably of about the same age; none show the peculiarities expected of HAeBe stars. Dereddened, their apparent V magnitudes lead to a distance of about 700pc. Radio observations suggest that the optical object LkH{alpha} 101 is in fact a hot star surrounded by a small H II region, both inside an optically thick dust shell.
- ID:
- ivo://CDS.VizieR/J/A+A/433/117
- Title:
- L- & M-band imaging of the Galactic Center
- Short Name:
- J/A+A/433/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric data of the sources detected in NAOS/CONICA H- and K-band (1.6 and 2.1{mu}m) and ISAAC L- and M-band (3.8 and 4.7{mu}m) images of the Galactic Center, obtained in May and August 2002, are presented. For each source, name (if relevant), position offset, H-, K-, L- and M-band magnitude (if available) and observed colors (H-K, K-L and L-M) are given. The position zero-point is RA = 17:45:40.26, DE = -29:00:29.91 (IRS 16NE) in the J2000 system, with an offset of 2.83" (RA) and -0.91" (DE) from Sgr A*. The total photometric accuracy is +/-0.25mag in H- and K-band, +/-0.15mag in L- and M-band, positional accuracy is +/-0.09".
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/2307
- Title:
- LMC anomalous Cepheid Ks light curves
- Short Name:
- J/MNRAS/437/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA near-infrared YJKs survey of the Magellanic Clouds System (VMC, PI M.-R. L. Cioni) is collecting deep Ks-band time-series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper, we present for the first time Ks-band light curves for anomalous Cepheid (AC) variables. In particular, we have analysed a sample of 48 Large Magellanic Cloud ACs, for which identification and optical magnitudes were obtained from the OGLE III and IV catalogues. The VMC Ks-band light curves for ACs are well sampled, with the number of epochs ranging from 8 to 16, and allowing us to obtain very precise mean Ks magnitudes with errors on average of the order of 0.01mag. The <Ks> values were used to build the first period-luminosity and period-Wesenheit relations in the near-infrared for fundamental mode and first overtone ACs. At the same time we exploited the optical (V, I) OGLE data to build accurate period-luminosity, period-luminosity-colour and period-Wesenheit relations both for fundamental mode and first overtone ACs. For the first time, these relations were derived from a sample of pulsators which uniformly cover the whole AC instability strip. The application of the optical period-Wesenheit relation to a sample of dwarf galaxies hosting a significant population of ACs revealed that this relation is a valuable tool for deriving distances within the Local Group. Due to its lower dispersion, we expect the Ks period-Wesenheit relations first derived in this paper to represent a valuable tool for measuring accurate distances to galaxies hosting ACs when more data in near-infrared filters become available.
- ID:
- ivo://CDS.VizieR/J/AJ/154/102
- Title:
- LMC blue supergiants spectroscopic observations
- Short Name:
- J/AJ/154/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-quality spectra of 90 blue supergiant stars in the Large Magellanic Cloud are analyzed with respect to effective temperature, gravity, metallicity, reddening, extinction, and extinction law. An average metallicity, based on Fe and Mg abundances, relative to the Sun of [Z]=-0.35+/-0.09 dex is obtained. The reddening distribution peaks at E(B-V)=0.08 mag, but significantly larger values are also encountered. A wide distribution of the ratio of extinction to reddening is found ranging from R_V_=2 to 6. The results are used to investigate the blue supergiant relationship between flux-weighted gravity, g_F_=g/T_eff_^4^, and absolute bolometric magnitude M_bol_. The existence of a tight relationship, the Flux-weighted Gravity-Luminosity Relationship (FGLR), is confirmed. However, in contrast to previous work, the observations reveal that the FGLR is divided into two parts with a different slope. For flux-weighted gravities larger than 1.30 dex, the slope is similar to that found in previous work, but the relationship becomes significantly steeper for smaller values of the flux-weighted gravity. A new calibration of the FGLR for extragalactic distance determinations is provided.
- ID:
- ivo://CDS.VizieR/J/AJ/124/2039
- Title:
- LMC Blue variable stars from MACHO
- Short Name:
- J/AJ/124/2039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric properties of 1280 blue variable stars within the Large Megallanic Cloud. Photometry is derived from the MACHO database. The light curves of the sample exhibit a variety of quasi-periodic and aperiodic outburst behavior. A characteristic feature of the photometric variation is that the objects are reddest when at maximum outburst. A subset of 102 objects were examined spectroscopically. Within this subset, 91% exhibited Balmer emission in at least one epoch, in some cases with spectacular spectral variability. The variability observed in the sample is consistent with the establishment and maintenance of the Be phenomenon.
- ID:
- ivo://CDS.VizieR/J/AJ/149/117
- Title:
- LMC infrared survey. I. Photometry of Cepheids
- Short Name:
- J/AJ/149/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observational details and first results of a near-infrared (JHK_s_) synoptic survey of the central region of the Large Magellanic Cloud (LMC) using the CPAPIR camera at the CTIO 1.5m telescope. We covered 18 square degrees to a depth of K_s_~16.5mag and obtained an average of 16 epochs in each band at any given location. Our catalog contains more than 3.5x10^6^ sources, including 1417 Cepheid variables previously studied at optical wavelengths by the OGLE survey. Our sample of fundamental-mode pulsators represents a nine-fold increase in the number of these variables with time-resolved, multi-band near-infrared photometry. We combine our large Cepheid sample and a recent precise determination of the distance to the LMC to derive a robust absolute calibration of the near-infrared Leavitt Law for fundamental-mode and first-overtone Cepheids with 10x better constraints on the slopes relative to previous work. We also obtain calibrations for the tip of the red giant branch and the red clump based on our ensemble photometry which are in good agreement with previous determinations.
