- ID:
- ivo://CDS.VizieR/J/ApJS/241/18
- Title:
- A 6.7GHz methanol maser survey. II. |b|<2{deg}
- Short Name:
- J/ApJS/241/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of our systematic survey for Galactic 6.7GHz Class II CH_3_OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky Wide-field Infrared Survey Explorer (WISE) point-source catalog. We discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e., |b|>2{deg}) in a previous paper (Paper I; Yang+ 2017, J/ApJ/846/160). Here, we present the results from the survey of those at low Galactic latitudes, i.e., |b|<2{deg}. Of 1875 selected WISE point sources, 291 positions that were actually associated with 224 sources that were detected with CH_3_OH maser emission. Among them, 32 are newly detected. A majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224=93.3%) are quite close to the Galactic Plane (|b|<1{deg}) and lie on the inner spiral arms with positive local standard of rest velocities. The detection rate and the color-color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalog of 1085 sources with 6.7GHz CH_3_OH maser emission in our Galaxy.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/751/52
- Title:
- AGN candidates from the WISE, 2MASS, RASS (W2R)
- Short Name:
- J/ApJ/751/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed the "S_IX_" statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3m Kast spectroscopy. We find that sources with S_IX_<0 have a >~95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the "W2R" sample of 4316 sources with S_IX_<0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J<~16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J<14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg^2^, permitting construction of AGN samples in any sufficiently large region of sky.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/104
- Title:
- AGN identifications from AKARI and Swift
- Short Name:
- J/ApJ/753/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22 month hard X-ray survey (Tueller et al. 2010, Cat. J/ApJS/186/378) with the AKARI all-sky survey (AKARI/PSCs; Ishihara et al. 2010, Cat. II/297; Yamamura et al. 2010, Cat. II/298), we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90{mu}m) and hard X-ray (14-195keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A135
- Title:
- AGN Opt/IR properties in Lockman Hole
- Short Name:
- J/A+A/529/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the observed-frame optical, near-, and mid-infrared properties of X-ray-selected active galactic nuclei (AGN) in the Lockman Hole. Using a likelihood ratio method on optical, near-infrared or mid-infrared catalogues, we assigned counterparts to 401 out of the 409 X-ray sources of the XMM-Newton catalogue. Accurate photometry was collected for all the sources from U to 24um. We used X-ray and optical criteria to remove any normal galaxies, galactic stars, or X-ray clusters among them and studied the multi-wavelength properties of the remaining 377 AGN. We used a mid-IR colour-colour selection to understand the AGN contribution to the optical and infrared emission.
- ID:
- ivo://CDS.VizieR/J/AJ/146/87
- Title:
- AGN photometry. II. A catalog from the CFHTLS
- Short Name:
- J/AJ/146/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of the series Detecting Active Galactic Nuclei Using Multi-filter Imaging Data. In this paper we review shapelets, an image manipulation algorithm, which we employ to adjust the point-spread function (PSF) of galaxy images. This technique is used to ensure the image in each filter has the same and sharpest PSF, which is the preferred condition for detecting AGNs using multi-filter imaging data as we demonstrated in Paper I of this series. We apply shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey ugriz images. Photometric parameters such as effective radii, integrated fluxes within certain radii, and color gradients are measured on the shapelets-reconstructed images. These parameters are used by artificial neural networks (ANNs) which yield: photometric redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy morphological types with an uncertainty less than 2 T types for z<=0.1; and identification of galaxies as AGNs with 70% confidence, star-forming/starburst (SF/SB) galaxies with 90% confidence, and passive galaxies with 70% confidence for z<=0.1. The incorporation of ANNs provides a more reliable technique for identifying AGN or SF/SB candidates, which could be very useful for large-scale multi-filter optical surveys that also include a modest set of spectroscopic data sufficient to train neural networks.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/508
- Title:
- 5000 AGNs behind the Magellanic clouds
- Short Name:
- J/ApJ/701/508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that using mid-IR color selection to find active galactic nuclei (AGNs) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the Spitzer Deep Wide Field Survey data for the NOAO Deep Wide Field Survey Bootes region and the SAGE Survey of the Large Magellanic Cloud. We use this to build high-purity catalogs of ~5000 AGN candidates behind the Magellanic Clouds. Once confirmed, these quasars will expand the available astrometric reference sources for the Clouds and the numbers of quasars with densely sampled, long-term (>decade) monitoring light curves by well over an order of magnitude and potentially identify sufficiently bright quasars for absorption line studies of the interstellar medium of the Clouds.
- ID:
- ivo://CDS.VizieR/J/ApJS/221/12
- Title:
- AGNs in the MIR using AllWISE data
- Short Name:
- J/ApJS/221/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an all-sky sample of ~1.4 million active galactic nuclei (AGNs) meeting a two-color infrared photometric selection criteria for AGNs as applied to sources from the Wide-field Infrared Survey Explorer final catalog release (AllWISE). We assess the spatial distribution and optical properties of our sample and find that the results are consistent with expectations for AGNs. These sources have a mean density of ~38 AGNs per square degree on the sky, and their apparent magnitude distribution peaks at g~20, extending to objects as faint as g~26. We test the AGN selection criteria against a large sample of optically identified stars and determine the "leakage" (that is, the probability that a star detected in an optical survey will be misidentified as a quasi-stellar object (QSO) in our sample) rate to be <=4.0x10^-5^. We conclude that our sample contains almost no optically identified stars (<=0.041%), making this sample highly promising for future celestial reference frame work as it significantly increases the number of all-sky, compact extragalactic objects. We further compare our sample to catalogs of known AGNs/QSOs and find a completeness value of >~84% (that is, the probability of correctly identifying a known AGN/QSO is at least 84%) for AGNs brighter than a limiting magnitude of R<~19. Our sample includes approximately 1.1 million previously uncataloged AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/772/26
- Title:
- AGN with WISE. II. The NDWFS Bootes field
- Short Name:
- J/ApJ/772/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stern et al. (2012ApJ...753...30S, Paper I) presented a study of Wide-field Infrared Survey Explorer (WISE) selection of active galactic nuclei (AGNs) in the 2deg^2^ COSMOS field, finding that a simple criterion W1-W2>=0.8 provides a highly reliable and complete AGN sample for W2<15.05, where the W1 and W2 passbands are centered at 3.4{mu}m and 4.6{mu}m, respectively. Here we extend this study using the larger 9deg^2^ NOAO Deep Wide-Field Survey Bootes field which also has considerably deeper WISE observations than the COSMOS field, and find that this simple color cut significantly loses reliability at fainter fluxes. We define a modified selection criterion combining the W1-W2 color and the W2 magnitude to provide highly reliable or highly complete AGN samples for fainter WISE sources. In particular, we define a color-magnitude cut that finds 130+/-4deg^-2^ AGN candidates for W2<17.11 with 90% reliability. Using the extensive UV through mid-IR broadband photometry available in this field, we study the spectral energy distributions of WISE AGN candidates. We find that, as expected, the WISE AGN selection can identify highly obscured AGNs, but that it is biased toward objects where the AGN dominates the bolometric luminosity output. We study the distribution of reddening in the AGN sample and discuss a formalism to account for sample incompleteness based on the step-wise maximum-likelihood method of Efstathiou et al. The resulting dust obscuration distributions depend strongly on AGN luminosity, consistent with the trend expected for a receding torus. At L_AGN_~3x10^44^erg/s, 29%+/-7% of AGNs are observed as Type 1, while at ~4x10^45^erg/s the fraction is 64%+/-13%. The distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A10
- Title:
- A grid of MARCS model atmospheres for S stars
- Short Name:
- J/A+A/601/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing asymptotic giant branch. A grid of MARCS model atmospheres has been computed for S stars, covering the range 2700<=Teff(K)<=4000, 0.50<=C/O<0.99, 0<=logg<=5, [Fe/H]=0., -0.5dex, and [s/Fe]= 0, 1, and 2 dex (where the latter quantity refers to the global overabundance of s-process elements). The MARCS models make use of a new ZrO line list. Synthetic spectra computed from these models are used to derive photometric indices in the Johnson and Geneva systems, as well as TiO and ZrO band strengths. A method is proposed to select the model best matching any given S star, a non-trivial operation since the grid contains more than 3500 models covering a five-dimensional parameter space. The method is based on the comparison between observed and synthetic photometric indices and spectral band strengths, and has been applied on a vast subsample of the Henize sample of S stars. Our results confirm the old claim by Piccirillo (1980MNRAS.190..441P) that ZrO bands in warm S stars (Teff > 3200K) are not caused by the C/O ratio being close to unity, as traditionally believed, but rather by some Zr overabundance. The TiO and ZrO band strengths, combined with V-K and J-K photometric indices, are used to select Teff, C/O, [Fe/H] and [s/Fe]. The Geneva U-B_1 and B_2-V_1 indices (or any equivalent) are good at selecting the gravity. The defining spectral features of dwarf S stars are outlined, but none is found among the Henize S stars. More generally, it is found that, at Teff=3200K, a change of C/O from 0.5 to 0.99 has a strong impact on V-K (2mag). Conversely, a range of 2 mag in V-K corresponds to a 200K shift along the (Teff, V-K) relationship (for a fixed C/O value). Hence, the use of a (Teff, V-K) calibration established for M stars will yield large errors for S stars, so that a specific calibration must be used, as provided in the present paper. Using the atmospheric parameters derived by our method for the sample of Henize S stars, we show that the extrinsic-intrinsic dichotomy among S stars reveals itself very clearly as a bimodal distribution in the effective temperatures. Moreover, the increase of s-process element abundances with increasing C/O ratios and decreasing temperatures is apparent among intrinsic stars, confirming theoretical expectations.
- ID:
- ivo://CDS.VizieR/J/AJ/139/434
- Title:
- A1763 infrared and optical photometry
- Short Name:
- J/AJ/139/434
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric analysis of the galaxy cluster Abell 1763 at visible and infrared wavelengths. Included are fully reduced images in r', J, H, and Ks obtained using the Palomar 200in telescope, as well as the IRAC and MIPS images from Spitzer. The cluster is covered out to approximately 3 virial radii with deep 24um imaging (a 5{sigma} depth of 0.2mJy). This same field of ~40'x40' is covered in all four IRAC bands as well as the longer wavelength MIPS bands (70 and 160um). The r' imaging covers ~0.8deg^2^ down to 25.5mag, and overlaps with most of the MIPS field of view. The J, H, and Ks images cover the cluster core and roughly half of the filament galaxies, which extend toward the neighboring cluster, Abell 1770. This first, in a series of papers on Abell 1763, discusses the data reduction methods and source extraction techniques used for each data set. We present catalogs of infrared sources (with 24 and/or 70um emission) and their corresponding emission in the optical (u', g', r', i', z'), and near- to far-IR (J, H, Ks, IRAC, and MIPS 160um). We provide the catalogs and reduced images to the community through the NASA/IPAC Infrared Science Archive.
