- ID:
- ivo://CDS.VizieR/J/ApJ/676/1281
- Title:
- L and T dwarfs in 2MASS/SDSS
- Short Name:
- J/ApJ/676/1281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new L and T dwarfs found in a cross-match of the SDSS Data Release 1 and 2MASS. Our simultaneous search of the two databases effectively allows us to relax the criteria for object detection in either survey and to explore the combined databases to a greater completeness level. We find two new T dwarfs in addition to the 13 already known in the SDSS DR1 footprint. We also identify 22 new candidate and bona fide L dwarfs, including a new young L2 dwarf and a peculiar potentially metal-poor L2 dwarf with unusually blue near-IR colors. These discoveries underscore the utility of simultaneous database cross-correlation in searching for rare objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/366/645
- Title:
- LARCS. 11 X-ray luminous clusters
- Short Name:
- J/MNRAS/366/645
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the spectroscopic and photometric catalogues of 11 X-ray luminous clusters at 0.07<z<0.16 from the Las Campanas/Anglo-Australian Telescope Rich Cluster Survey. Our spectroscopic data set consists of over 1600 galaxy cluster members, of which two-thirds are outside r_200_. These spectra allow us to assign cluster membership using a detailed mass model and expand on our previous work on the cluster colourmagnitude relation (CMR) where membership was inferred statistically.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A44
- Title:
- Large-amplitude variables in Gaia DR2
- Short Name:
- J/A+A/648/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric variability is an essential feature that sheds light on the intrinsic properties of celestial variable sources, the more so when photometry is available in various bands. In this respect, the all-sky Gaia mission is particularly attractive as it collects, among other quantities, epoch photometry measured quasi-simultaneously in three optical bands for sources ranging from a few magnitudes to fainter than magnitude twenty. The second data release (DR2) of the mission provides mean G, GBP and GRP photometry for 1.4 billion sources, but light curves and variability properties are available for only 0.5 million of them. Here, we provide a census of large-amplitude variables (LAVs) with amplitudes larger than 0.2mag in the G band for objects with mean brightnesses between 5.5 and 19mag. To achieve this, we rely on variability amplitude proxies in G, GBP and GRP computed from the uncertainties on the magnitudes published in DR2. We then apply successive filters to identify two subsets containing respectively sources with reliable mean GBP and GRP (for studies using colours) and sources having compatible amplitude proxies in G, GBP and GRP (for multi-band variability studies). The full catalogue gathers 23315874 LAV candidates, and the two subsets with increased levels of purity contain respectively 1148861 and 618966 sources. A multi-band variability analysis of the catalogue shows that different types of variable stars can be categorized according to their colour and blue-to-red amplitude ratios as determined from the G, GBP and GRP amplitude proxies. More specifically, four groups are globally identified. They mostly include long-period variables in a first group with amplitudes more than twice larger in the blue than in the red, hot compact variables in a second group with amplitudes smaller in the blue than in the red, classical instability strip pulsators in a third group with amplitudes larger in the blue than in the red by 50% to 80%, and other non-pulsating variables in a fourth group, mainly achromatic, but with still 10% of them having 20% to 50% larger amplitudes in the blue than in the red. The catalogue constitutes the first census of Gaia large amplitude variable (LAV) candidates, extracted from the public DR2 archive. The overview presented here illustrates the added-value of the mission for multi-band variability studies even at this stage when epoch photometry is not yet available for all sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/321/77
- Title:
- Large-amplitude variables near the Galactic Centre
- Short Name:
- J/MNRAS/321/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report here the results of a 4-yr K-band (2.2mm) survey for large-amplitude variable stars in a 24x24arcmin^2^ area centred on the Galactic Centre. A total of 409 likely long-period variables (LPVs) were detected, for which positions, amplitudes, average magnitudes and periods were obtained whenever possible. The surface density of LPVs is more than ten times greater than in the Sgr I Baade window at l=-1.37{deg}, b=-2.63{deg}
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2876
- Title:
- Large area KX quasar catalogue
- Short Name:
- J/MNRAS/424/2876
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a large area, ~600deg^2^, K-band flux-limited spectroscopic survey for luminous quasars are presented. The survey utilizes the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) in regions of sky within the Sloan Digital Sky Survey (SDSS) footprint. The K-band excess (KX) of all quasars with respect to Galactic stars is exploited in combination with a photometric redshift/classification scheme to identify quasar candidates for spectroscopic follow-up observations. The data contained within this investigation will be able to provide new constraints on the fraction of luminous quasars reddened by dust with E(B-V)<=0.5mag. The spectroscopic sample is defined using the K-band, 14.0<=K<=16.6, and SDSS i-band limits of i=19.5, 19.7 and 22.0 over sky areas of 287, 150 and 196deg^2^, respectively. The survey includes >3200 known quasars from the SDSS and more than 250 additional confirmed quasars from the KX selection. A well-defined subsample of quasars in the redshift interval 1.0<=z<=3.5 includes 1152 objects from the SDSS and 172 additional KX-selected quasars. The quasar selection is >95 per cent complete with respect to known SDSS quasars and >95 per cent efficient, largely independent of redshift and i-band magnitude. The properties of the new KX-selected quasars confirm the known redshift-dependent effectiveness of the SDSS quasar selection and provide a sample of luminous quasars experiencing intermediate levels of extinction by dust. The catalogue represents an important step towards the assembly of a well-defined sample of luminous quasars that may be used to investigate the properties of quasars experiencing intermediate levels of dust extinction within their host galaxies or due intervening absorption line systems.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A140
- Title:
- Large Quasar Astrometric Catalogue 4, LQAC-4
- Short Name:
- J/A+A/614/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From an astrometric point of view, quasars constitute the best and almost ideal reference objects in the celestial sphere, with a priori no significant proper motion. Since the third release of the Large Quasar Astrometric Catalogue (LQAC-3, Cat. J/A+A/583/A75), a large number of quasars have been discovered, in particular those coming from the DR12Q release of the SDSS (Paris et al., 2017, Cat. VII/279). Moreover, for cross-matched objects, we have taken advantage of the very accurate determinations of the quasars identified within the recent Gaia DR1 catalogue (2018, Cat. I/345). Following the same procedure as in the three previous releases of the LQAC, our aim is to compile the large majority of all the quasars recorded so far. Our goal is to record their best coordinates and substantial information concerning their physical properties such as the redshift as well as multi-bands apparent and absolute magnitudes. Emphasis is given to the results of the cross-matches with the Gaia DR1 catalogue. New quasars coming from the DR12Q release were cross-matched with the precedent LQAC-3 compilation with a 1" search radius, in order to add the objects without counterpart to the LQAC-4 compilation. A similar cross-match was done with Gaia DR1 to identify the known quasars detected by Gaia. This enables one to improve significantly the positioning of these objects, and in parallel to study the astrometric performance of the individual catalogues of the LQAC-4 compilation. Finally, a new method was used to determine absolute magnitudes. Our final catalogue, called LQAC-4, contains 443 725 objects. This is roughly 37.82% more than the number of objects recorded in the LQAC-3. Among them, 249071 were found in common with the Gaia DR1, with a 1" search radius. That corresponds to 56.13% of the whole population in the compilation. The LQAC-4 delivers to the astronomical community a nearly complete catalogue of spectroscopically confirmed quasars (including a small proportion of compact AGNs), with the aim of giving their best equatorial coordinates with respect to the ICRF2 and with exhaustive additional information. For more than 50% of the sample, these coordinates come from the very recent Gaia DR1.
- ID:
- ivo://CDS.VizieR/J/A+A/537/A99
- Title:
- Large Quasar Astrometric Catalogue 2 (LQAC-2)
- Short Name:
- J/A+A/537/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- First of all we make a substantial review of the definitions and properties of quasars and AGN (Active Galactic Nuclei), the differenciation of these objects being unclear in the literature and even for specialists. This will serve our purpose when deciding which kinds of objects will be taken into account in our compilation. Then we carry out the cross-identification between the 9 catalogues of quasars chosen for their accuracy and their huge number of objects, using a flag for each of them, and including all the available data related to magnitudes (infrared and optical), radiofluxes and redshifts. We also perform cross identification with external catalogues 2MASS, B1.0 and GSC2.3 in order to complete photometric data of the objects. Moreover we compute the absolute magnitude of our extragalactic objects by taking into account the recent studies concerning the galactic absorption. In addition substantial improvements are brought with respect to the first release of the LQAC (Souchay et al., 2009, Cat. J/A+A/494/799). At first a LQAC name is given for each object based on its equatorial coordinates with respect to the ICRS, following a procedure which creates no ambiguity for identification. At second the equatorial coordinates of the objects are recomputed more accurately according to the algorithms used for the elaboration of the Large Quasar Reference Frame (LQRF) (Andrei et al., 2009, Cat. I/313). At third we introduce a morphological classification for the objects which enables in particular to define clearly if the object is point-like or extended. Our final catalogue, called LQAC-2, contains 187 504 quasars. This is roughly larger than the 113 666 quasars recorded in the first version of the LQAC (Souchay et al., 2009, Cat. J/A+A/494/799) and a little more than the number of quasars recorded in the up-dated version of the Veron Cetty and Veron (2010, Cat. VII/258) catalogue, which was the densest compilation of quasars up to now. In addition to the quantitative and qualitative improvements brought by our compilation, we discuss the homogeneity of the data and carry out statistical analysis concerning the spatial density and the distance to the closest neighbour.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A75
- Title:
- Large Quasar Astrometric Catalogue 3 (LQAC-3)
- Short Name:
- J/A+A/583/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From an astrometric point of view, quasars constitute quasi-ideal reference objects in the celestial sphere, with an a priori absence of proper motion. Since the second release of the Large Quasar Astrometric Catalog (LQAC), a large number of quasars have been discovered, in particular with the upcoming new release of the SDSS quasars catalog. Following the same procedure as in the two previous releases of the LQAC, our aim was to compile all the quasars recorded until the present date, with accurate recomputation of their equatorial coordinates in the ICRS and with the maximum of information concerning their physical properties, such as the redshift, the photometry, and the absolute magnitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/494/799
- Title:
- Large Quasar Astrometric Catalogue (LQAC)
- Short Name:
- J/A+A/494/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The very large and increasing number of quasars reckoned from various sky surveys leads to a large quantity of data which brings various and inhomogeneous information in the fields of astrometry, photometry, radioastronomy and spectroscopy. In this paper, we describe our work that aims to make available a general compilation of the largest number of recorded quasars obtained from all the available catalogues, with their best position estimates, and providing physical information at both optical and radio wavelengths.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A166
- Title:
- Large scale mechanical heating in NGC4945
- Short Name:
- J/A+A/642/A166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the dominant heating mechanism in the nuclei of galaxies is crucial to understand star formation in starbursts (SB), active galactic nuclei (AGN) phenomena and the relationship between the star formation and AGN activity in galaxies. The analysis of the carbon monoxide (^12^CO) rotational ladder versus the infrared continuum emission (hereafter, ^12^CO/IR) in galaxies with different type of activity have shown important differences between them. We aim at carrying out a comprehensive study of the nearby composite AGN-SB galaxy, NGC 4945, using spectroscopic and photometric data from the Herschel satellite. In particular, we want to characterize the thermal structure in this galaxy by a multi-transitions analysis of the spatial distribution of the ^12^CO emission at different spatial scales. We also want to establish the dominant heating mechanism at work in the inner region of this object at smaller spatial scales (<~200pc). We present far-infrared (FIR) and sub-millimeter (sub-mm) ^12^CO line maps and single spectra (from J_up_=3 to 20) using the Heterodyne Instrument for the Far Infrared (HIFI), the Photoconductor Array Camera and Spectrometer (PACS), and the Spectral and Photometric Imaging REceiver (SPIRE) onboard Herschel, and the Atacama Pathfinder EXperiment (APEX). We combined the ^12^CO/IR flux ratios and the local thermodynamic equilibrium (LTE) analysis of the ^12^CO images to derive the thermal structure of the Interstellar Medium (ISM) for spatial scales raging from <~200pc to 2kpc. In addition, we also present single spectra of low (^12^CO, ^13^CO and [CI]) and high density (HCN, HNC, HCO^+^, CS and CH) molecular gas tracers obtained with APEX and HIFI applying LTE and non-LTE analyses. Furthermore, the Spectral Energy Distribution (SED) of the continuum emission from the far-IR to sub-mm wavelengths is also presented. From the non-LTE analysis of the low and high density tracers we derive in NGC 4945 gas volume densities (10^3^-10^6^cm^-3^) similar to those found in other galaxies with different type of activity. From the ^12^CO analysis we found clear trend in the distribution of the derived temperatures and the ^12^CO/IR ratios. It is remarkable that at intermediate scales (360pc-1kpc, or 19"-57") we see large temperatures in the direction of the X-ray outflow while at smaller scales (<~200pc-360pc, or 9"-19"), the highest temperature, derived from the high-J lines, is not found toward the nucleus, but toward the galaxy plane. The thermal structure derived from the ^12^CO multi-transition analysis suggests that mechanical heating, like shocks or turbulence, dominates the heating of the ISM in the nucleus of NGC4945 located beyond 100 pc (&500) from the center of the galaxy. This result is further supported by the Kazandjian et al. (2015, Cat. J/AJ/133/504) models, which are able to reproduce the emission observed at high-J (PACS) ^12^CO transitions when mechanical heating mechanisms are included. Shocks and/or turbulence are likely produced by the barred potential and the outflow, observed in X-rays.
