- ID:
- ivo://CDS.VizieR/J/ApJ/894/75
- Title:
- Ultra-diffuse & LSB dwarf galaxies in A370 from HFF
- Short Name:
- J/ApJ/894/75
- Date:
- 19 Jan 2022 13:03:46
- Publisher:
- CDS
- Description:
- We report the discovery of ultra-diffuse galaxies (UDGs) in Abell 370 (A370; z=0.375). We find 46 UDGs in A370 from the images of the Hubble Frontier Fields. Most UDGs are low-luminosity red sequence galaxies, while a few of them are blue UDGs. We estimate the abundance of UDGs in A370, N(UDG)=644+/-104. Combining these results with those of Abell S1063 (z=0.348) and Abell 2744 (z=0.308), we derive a mean radial number density profile of UDGs in the three clusters. The number density profiles of UDGs and bright galaxies show a discrepancy in the central region of the clusters: the profile of UDGs shows a flattening as clustercentric distance decreases, while that of bright galaxies shows a continuous increase. This implies that UDGs are prone to disruption in the central region of the clusters. The relation between the abundance of UDGs and virial masses of their host systems is described by a power law with an index of nearly one: N(UDG){propto}M_200_^0.99+/-0.05^ for M_200_>10^13^M_{sun}_. We estimate approximately dynamical masses of UDGs using the fundamental manifold method and find that most UDGs have dwarf-like masses (M_200_<10^11^M_{sun}_). This implies that most UDGs have a dwarf-like origin and a small number of them could be failed L* galaxies. These results suggest that multiple origins may contribute to the formation and evolution of UDGs in massive galaxy clusters.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/704/789
- Title:
- Ultra-luminous infrared galaxies in SDSS-DR6
- Short Name:
- J/ApJ/704/789
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-luminous infrared galaxies (ULIRGs) are interesting objects with dramatic properties. Many efforts have been made to understand the physics of their luminous infrared emission and evolutionary stages. However, a large ULIRG sample is still needed to study the properties of their central black holes (BHs), the BH-host galaxy relation, and their evolution. We identified 308 ULIRGs from the Sloan Digital Sky Survey Data Release 6, and classified them into the NL ULIRGs (with only narrow emission lines) and the Type I ULIRGs (with broad emission lines). About 56% of ULIRGs in our total sample show interaction features, and this percentage is 79% for redshift z<0.2. Optical identifications of these ULIRGs show that the active galactic nucleus percentage is at least 49%, and the percentage increases with the infrared luminosity. We found 62 Type I ULIRGs, and estimated their BH masses and velocity dispersions from their optical spectra. Together with known Type I ULIRGs in the literature, a sample of 90 Type I ULIRGs enables us to make a statistical study.
- ID:
- ivo://CDS.VizieR/J/MNRAS/279/459
- Title:
- Ultraluminous IRAS galaxies
- Short Name:
- J/MNRAS/279/459
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new, large sample of ultraluminous (L_60_>10^11.4^L_{sun}_ for H_0_=100km/s/Mpc) IRAS galaxies selected for the IRAS Faint Source Survey using a novel optical far-infrared colour selection criterion. Our technique proves to be very successful in selecting luminous galaxies, and we present data on 91 ultraluminous objects, of which 65 are newly discovered. Using our redshift spectra and information from the literature we find that at least 35% of these objects are likely to contain an AGN-type central engine. We also find that purely IR-based techniques for determining the presence of an AGN in these objects are unreliable.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/470
- Title:
- ULX candidates in luminous infrared galaxies
- Short Name:
- J/MNRAS/446/470
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a Chandra study of ultraluminous X-ray sources (ULXs) in a sample of 17 nearby (D_L_<60Mpc) luminous infrared galaxies (LIRGs), selected to have star formation rates (SFRs) in excess of 7M_{sun}_/yr and low foreground Galactic column densities (N_H_<~5x10^20^cm^-2^). A total of 53 ULXs were detected and we confirm that this is a complete catalogue of ULXs for the LIRG sample. We examine the evolution of ULX spectra with luminosity in these galaxies by stacking the spectra of individual objects in three luminosity bins, finding a distinct change in spectral index at luminosity ~2x10^39^erg/s. This may be a change in spectrum as 10M_{sun}_ black holes transit from an ~ Eddington to a super-Eddington accretion regime, and is supported by a plausible detection of partially ionized absorption imprinted on the spectrum of the luminous ULX (L_X_~5x10^39^erg/s) CXOU J024238.9-000055 in NGC 1068, consistent with the highly ionized massive wind that we would expect to see driven by a super-Eddington accretion flow. This sample shows a large deficit in the number of ULXs detected per unit SFR (0.2 versus 2 ULXs, per M_{sun}_/yr) compared to the detection rate in nearby (D_L_<14.5Mpc) normal star-forming galaxies. This deficit also manifests itself as a lower differential X-ray luminosity function normalization for the LIRG sample than for samples of other star-forming galaxies. We show that it is unlikely that this deficit is a purely observational effect. Part of this deficit might be attributable to the high metallicity of the LIRGs impeding the production efficiency of ULXs and/or a lag between the star formation starting and the production of ULXs; however, we argue that the evidence - including very low N_ULX_/L_FIR_, and an even lower ULX incidence in the central regions of the LIRGs - shows that the main culprit for this deficit is likely to be the high column of gas and dust in these galaxies, that fuels the high SFR but also acts to obscure many ULXs from our view.
- ID:
- ivo://CDS.VizieR/J/AJ/143/144
- Title:
- ULX candidates in nearby Arp galaxies
- Short Name:
- J/AJ/143/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a statistical analysis of the ultra-luminous X-ray point sources (ULXs; L_X_>=10^39^erg/s) in a sample of galaxies selected from the Arp Atlas of Peculiar Galaxies (1996, Cat. VII/192; Webb, 1996, Cat. VII/192). We find a possible enhancement of a factor of ~2-4 in the number of ULXs per blue luminosity for the strongly interacting subset. Such an enhancement would be expected if ULX production is related to star formation, as interacting galaxies tend to have enhanced star formation rates on average. For most of the Arp galaxies in our sample, the total number of ULXs compared to the far-infrared luminosity is consistent with values found earlier for spiral galaxies. This suggests that for these galaxies, ULXs trace recent star formation. However, for the most infrared-luminous galaxies, we find a deficiency of ULXs compared to the infrared luminosity. For these very infrared-luminous galaxies, active galactic nuclei may contribute to powering the far-infrared; alternatively, ULXs may be highly obscured in the X-ray in these galaxies and therefore not detected by these Chandra observations. We determined local UV/optical colors within the galaxies in the vicinity of the candidate ULXs using Galaxy Evolution Explorer UV and Sloan Digitized Sky Survey optical images. In most cases, the distributions of colors are similar to the global colors of interacting galaxies. However, the u-g and r-i colors at the ULX locations tend to be bluer on average than these global colors, suggesting that ULXs are preferentially found in regions with young stellar populations. In the Arp sample there is a possible enhancement of a factor of ~2-5 in the fraction of galactic nuclei that are X-ray-bright compared to more normal spirals.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/71
- Title:
- ULXs with multiepoch Spitzer/IRAC obs.
- Short Name:
- J/ApJ/878/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a mid-infrared (IR) sample study of nearby ultraluminous X-ray sources (ULXs) using multiepoch observations with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. Spitzer/IRAC observations taken after 2014 were obtained as part of the Spitzer Infrared Intensive Transients Survey. Our sample includes 96 ULXs located within 10 Mpc. Of the 96 ULXs, 12 have candidate counterparts consistent with absolute mid-IR magnitudes of supergiants, and 16 counterparts exceeded the mid-IR brightness of single supergiants and are thus more consistent with star clusters or non-ULX background active galactic nuclei. The supergiant candidate counterparts exhibit a bimodal color distribution in a Spitzer/IRAC color-magnitude diagram, where "red" and "'blue" ULXs fall in IRAC colors [3.6]-[4.5]~0.7 and [3.6]-[4.5]~0.0, respectively. The mid-IR colors and absolute magnitudes of four "red" and five "blue" ULXs are consistent with those of supergiant B[e] (sgB[e]) and red supergiant (RSG) stars, respectively. Although "blue," RSG-like mid-IR ULX counterparts likely host RSG mass donors; we propose that "red" counterparts are ULXs exhibiting the "B[e] phenomenon" rather than hosts of sgB[e] mass donors. We show that the mid-IR excess from the "red" ULXs is likely due to thermal emission from circumstellar or circumbinary dust. Using dust as a probe for total mass, we estimate mass-loss rates of dM/dt~1x10^-4^M_{sun}_/yr in dust-forming outflows of red ULXs. Based on the transient mid-IR behavior and its relatively flat spectral index, {alpha}=-0.19+/-0.1, we suggest that the mid-IR emission from Holmberg IX X-1 originates from a variable jet.
- ID:
- ivo://CDS.VizieR/J/PASJ/61/177
- Title:
- 15um AKARI observations in CDFS field
- Short Name:
- J/PASJ/61/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep observations of the Chandra Deep Field South have been secured at 15um with AKARI/IRC infrared space telescope. From these observations, we define a sample of mid infrared-selected galaxies at 15um and we also obtain 15um flux densities for a sample of Lyman Break Galaxies at z~1 already observed at 24um with Spitzer/MIPS.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3199
- Title:
- 24um fluxes of GOODS-S AGN
- Short Name:
- J/MNRAS/446/3199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of galaxies showing mid-infrared variability in data taken in the deepest Spitzer/MIPS 24{mu}m surveys in the Great Observatory Origins Deep Survey South field. We divide the data set in epochs and subepochs to study the long-term (months-years) and the short-term (days) variability. We use a {chi}^2^-statistics method to select active galactic nucleus (AGN) candidates with a probability <=1% that the observed variability is due to statistical errors alone. We find 39 (1.7% of the parent sample) sources that show long-term variability and 55 (2.2% of the parent sample) showing short-term variability. That is, 0.03sources/arcmin^2^ for both, long-term and short-term variable sources. After removing the expected number of false positives inherent to the method, the estimated percentages are 1.0 and 1.4% of the parent sample for the long term and short term, respectively. We compare our candidates with AGN selected in the X-ray and radio bands, and AGN candidates selected by their IR emission. Approximately, 50% of the MIPS (Multiband Imaging Photometer for Spitzer) 24{mu}m variable sources would be identified as AGN with these other methods. Therefore, MIPS 24{mu}m variability is a new method to identify AGN candidates, possibly dust obscured and low-luminosity AGN, that might be missed by other methods. However, the contribution of the MIPS 24{mu}m variable identified AGN to the general AGN population is small (<=13%) in GOODS-South.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/370
- Title:
- 24um flux-limited sample of galaxies
- Short Name:
- J/ApJ/693/370
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mid-infrared spectroscopic analysis of a flux-limited sample of galaxies with f_{nu}_(24um)>10mJy is presented. Sources observed are taken from the Spitzer First Look Survey (FLS) catalog and from the NOAO Deep Wide-Field Survey region in Bootes (NDWFS). The spectroscopic sample includes 60 of the 100 sources in these combined catalogs having f_{nu}_(24um)>10 mJy. New spectra from the Spitzer Infrared Spectrograph are presented for 25 FLS sources and for 11 Bootes active galactic nuclei (AGNs); these are combined with 24 Bootes starburst galaxies previously published to determine the distribution of mid-infrared spectral characteristics for the total 10mJy sample. Sources have 0.01<z<2.4 and 41.8<log{nu}L_{nu}_(15um)<46.2(ergs/s).
1130. 11.5um image of NGC 835
- ID:
- ivo://CDS.VizieR/J/A+A/587/A1
- Title:
- 11.5um image of NGC 835
- Short Name:
- J/A+A/587/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Obscured active galactic nuclei (AGNs) are thought to be very common in the Universe. Observations and surveys have shown that the number of sources increases for near galaxies and at the low-luminosity regime (the so-called LLAGNs). Furthermore, many AGNs show changes in their obscuration properties at X-rays that may suggest a configuration of clouds very close to the accretion disk. However, these variations could also be due to changes in the intrinsic continuum of the source. It is therefore important to study nearby AGN to better understand the locus and distribution of clouds in the neighbourhood of the nucleus. We aim to study the nuclear obscuration of LLAGN NGC 835 and its extended emission using mid-infrared observations. We present sub-arcsecond-resolution mid-infrared 11.5um imaging of the LLAGN galaxy NGC 835 obtained with the instrument CanariCam in the Gran Telescopio CANARIAS (GTC), archival Spitzer/IRS spectroscopy, and archival Chandra data observed in 2000, 2008, and 2013.