- 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.
Number of results to display per page
Search Results
- 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).
- ID:
- ivo://CDS.VizieR/J/AJ/90/2221
- Title:
- UMi dwarf galaxy BV photometry
- Short Name:
- J/AJ/90/2221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed a color-magnitude diagram of the Ursa Minor dwarf spheroidal to m_V_=24.8mag from charged-coupled device (CCD) observations with the Kitt Peak 4 m telescope. The main-sequence turnoff is easily visible. Fits to evolutionary isochrones and the globular M92 indicate that Ursa Minor has an age and metal abundance very similar to that of the latter cluster. No evidence for stars younger than about 16 billion years is seen, with the possible exception of approximately 20 stars believed to be blue stragglers. Ursa Minor is therefore an extreme-age galaxy, unlike superficially similar objects such as the Carina dwarf. Indeed, Ursa Minor may be the only outer-halo spheroidal whose stellar content lives up to the classical ideals of a Population II system. A distance modulus of (m-M)_0_=19.0mag is derived from a sliding fit to the M92 ridge lines. However, this modulus is uncertain by ~0.1mag, for the horizontal branch in our color-magnitude diagram is poorly populated. The ratio of blue stragglers to anomalous Cepheids in Ursa Minor is estimated to be ~100, a number that may provide an important constraint on binary models for the origin of these stars. A surprising result of our study is the discovery of clumpiness in the distribution of stars. This finding may give more weight to the idea that dwarf spheroidal galaxies were previously dwarf irregular galaxies, although clearly, if so, Ursa Minor must have lost its gaseous content very soon after formation.
7424. 8.6um imaging of 47 Tuc
- ID:
- ivo://CDS.VizieR/J/A+A/537/A2
- Title:
- 8.6um imaging of 47 Tuc
- Short Name:
- J/A+A/537/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is an ongoing debate regarding the onset luminosity of dusty mass loss in population-II red giant stars. We present VLT/VISIR mid-infrared (MIR) 8.6um imaging of 47 Tuc, the centre of attention of a number of space-based Spitzer observations and studies. The VISIR high-resolution (diffraction limited) observations allow excellent matching to existing optical Hubble Space Telescope catalogues. The optical-MIR coverage of the inner core of the cluster provide the cleanest possible blending-free sampling of the upper 3mag of the giant branch. Our diagrams show no evidence of faint giants with MIR-excess. A combined near/mid-infrared diagram additionally confirms the near absence of dusty red giants. Dusty red giants and asymptotic giant stars are confined to the 47 Tuc long-period variable population. In particular, dusty red giants are limited to the upper one N8.6um magnitude below the giant branch tip. This particular luminosity level corresponds to ~1000L_{sun}_, which was suggested in previous determinations to mark the onset of dusty mass loss. Interestingly, starting from this luminosity level we detected a gradual deviation between the colours of red giants and the theoretical isochrones.
- ID:
- ivo://CDS.VizieR/J/A+A/475/791
- Title:
- 12um ISOCAM survey of the ESO-Sculptor field
- Short Name:
- J/A+A/475/791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed reduction of a mid-infrared 12um (LW10 filter) ISOCAM open time observation performed on the ESO-Sculptor Survey field (Arnouts et al., 1997A&AS..124..163A). A complete catalogue of 142 sources (120 galaxies and 22 stars), detected with high significance (equivalent to 5{sigma}), is presented above an integrated flux density of 0.31mJy. Star/galaxy separation is performed by a detailed study of colour-colour diagrams. The catalogue is complete to 1mJy and, below this flux density, the incompleteness is corrected using two independent methods. The first method uses stars and the second uses optical counterparts of the ISOCAM galaxies; these methods yield consistent results. We also apply an empirical flux density calibration using stars in the field. For each star, the 12um flux density is derived by fitting optical colours from a multi-band {chi}^2^ to stellar templates (BaSel-2.0) and using empirical optical-IR colour-colour relations. This article is a companion analysis to our 2007 paper (Rocca-Volmerange et al. 2007A&A...475..801R) where the 12um faint galaxy counts are presented and analysed per galaxy type with the evolutionary code PEGASE.3.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/98
- Title:
- 24um observations of AFGKM stars of 3 clusters
- Short Name:
- J/ApJ/750/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Spitzer Space Telescope 24 {mu}m data to search for debris disks among 122 AFGKM stars from the ~670 Myr clusters Hyades, Coma Ber, and Praesepe, utilizing a number of advances in data reduction and determining the intrinsic colors of main-sequence stars. For our sample, the 1{sigma} dispersion about the main-sequence V-K_S_, K_S_-[24] locus is approximately 3.1%. We identify seven debris disks at 10% or more ( >=3{sigma} confidence level) above the expected K_S_-[24] for purely photospheric emission. The incidence of excesses of 10% or greater in our sample at this age is 5.7^+3.1^_-1.7_%. Combining with results from the literature, the rate is 7.8^+4.2^_-2.1_% for early-type (B9-F4) stars and 2.7^+3.3^_-1.7_% for solar-like (F5-K9) stars. Our primary sample has strict criteria for inclusion to allow comparison with other work; when we relax these criteria, three additional debris disks are detected. They are all around stars of solar-like type and hence reinforce our conclusion that disks around such stars are still relatively common at 670Myr and are similar to the rate around early-type stars. The apparently small difference in decay rates between early-type and solar-like stars is inconsistent with the first-order theoretical predictions that the later type stellar disks would decay an order of magnitude more quickly than the earlier type ones.
- ID:
- ivo://CDS.VizieR/J/A+AS/101/59
- Title:
- 1-20um observations of Herbig-Haro objects
- Short Name:
- J/A+AS/101/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For 58 exciting sources of Herbig-Haro objects/jets (HHES) we present a catalogue of photometric data for the infrared spectral bands JHKLMNQ (1-20 um). This catalog is based on our own observations and published information available up to May 1992. For each source, these data are presented in chronological order. In addition to the broad-band data, narrow-band N(8-13 um) photometric data are also provided. The flux calibration for each observational equipment is explicitly noted as the diaphragm sizes are used. The same kind of information for the established members of the FU Ori class is complementing the HHES catalogue. The frequency of observations and the photometric quality of the catalogued data are shortly discussed.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/1
- Title:
- 500um risers with HerMES & SPIRE drop-outs with S2CLS
- Short Name:
- J/ApJS/249/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our systematic search for the reddest far-infrared (FIR) and submillimeter (sub-mm) galaxies using the data from the Herschel Multi-tiered Extragalactic Survey (HerMES) and the SCUBA2 Cosmological Legacy Survey (S2CLS). The red FIR galaxies are "500{mu}m risers," whose spectral energy distributions increase with wavelength across the three FIR passbands of the Spectral and Photometric Imaging REceiver (SPIRE) of Herschel. Within 106.5deg^2^ of the HerMES fields, we have selected 629 500{mu}m risers. The red sub-mm galaxies are "SPIRE drop-outs," which are prominent detections in the S2CLS 850{mu}m data but are extremely weak or invisible in the SPIRE bands. Within the 2.98deg^2^ common area of HerMES and S2CLS, we have selected 95 such objects. These very red sources could be dusty starbursts at high redshifts (z>~4-6) because the peak of their cold-dust emission heated by star formation is shifted to the reddest FIR/sub-mm bands. The surface density of 500{mu}m risers is ~8.2deg^-2^ at the >=20mJy level in 500{mu}m, while that of SPIRE drop-outs is ~19.3deg^-2^ at the >=5mJy level in 850{mu}m. Both types of objects could span a wide range of redshifts, however. Using deep radio data in these fields to further select the ones likely at the highest redshifts, we find that the surface density of z>6 candidates is 5.5deg^-2^ among 500{mu}m risers and is 0.8-13.6deg^-2^ among SPIRE drop-outs. If this is correct, the dust-embedded star formation processes in such objects could contribute comparably as Lyman-break galaxies to the global SFR density at z>6.
- 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.
- 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.
