- ID:
- ivo://CDS.VizieR/J/ApJ/723/993
- Title:
- Spatial extent of (U)LIRGs in the MIR. I.
- Short Name:
- J/ApJ/723/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the extended mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey sample based on 5-15um low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for the galaxies in the sample, FEE_{lambda}_, defined as the fraction of the emission which originates outside of the unresolved component of a source at a given distance. We find that the FEE_{lambda}_ varies from one galaxy to another, but we can identify three general types of FEE_{lambda}_: one where FEE_{lambda}_ is constant, one where features due to emission lines and polycyclic aromatic hydrocarbons appear more extended than the continuum, and a third which is characteristic of sources with deep silicate absorption at 9.7um. The mean size of the LIRG cores at 13.2um is 2.6kpc. However, once the IR luminosity of the systems reaches the threshold of L_IR_~10^11.8^L_{sun}_, slightly below the regime of Ultra-luminous Infrared Galaxies (ULIRGs), all sources become clearly more compact, with FEE_13.2um_<~0.2, and their cores are unresolved. Our estimated upper limit for the core size of ULIRGs is less than 1.5kpc.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/741/32
- Title:
- Spatial extent of (U)LIRGs in the MIR. II.
- Short Name:
- J/ApJ/741/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the second part of our analysis of the extended mid-infrared (MIR) emission of the GOALS sample based on 5-14um low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for all galaxies in the sample, FEE_{lambda}_, defined as the fraction of the emission that originates outside of the unresolved central component of a source, and spatially separate the MIR spectrum of a galaxy into its nuclear and extended components. We find that the [NeII]12.81um emission line is as compact as the hot dust MIR continuum, while the polycyclic aromatic hydrocarbon (PAH) emission is more extended. In addition, the 6.2 and 7.7um PAH emission is more compact than that of the 11.3um PAH, which is consistent with the formers being enhanced in a more ionized medium. The presence of an active galactic nucleus (AGN) or a powerful nuclear starburst increases the compactness and the luminosity surface density of the hot dust MIR continuum, but has a negligible effect on the spatial extent of the PAH emission on kpc-scales. Furthermore, it appears that both processes, AGN and/or nuclear starburst, are indistinguishable in terms of how they modify the integrated PAH-to-continuum ratio of the FEE in (ultra)luminous infrared galaxies ((U)LIRGs). Globally, the 5-14um spectra of the extended emission component are homogeneous for all galaxies in the GOALS sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/5179
- Title:
- Spatially offset AGN cand. in CLASS survey
- Short Name:
- J/MNRAS/475/5179
- Date:
- 02 Nov 2021 11:24:39
- Publisher:
- CDS
- Description:
- Prompted by a recent claim by Barrows et al. that X-ray active galactic nuclei (AGNs) are often found significantly offset from the centres of their host galaxies, we have looked for examples of compact radio sources that are offset from the optical centroids of nearby (z<0.2) galaxies. We have selected a sample of 345 galaxies from the Sloan Digital Sky Survey (SDSS) galaxy catalogue, which have nearby compact radio sources listed in the Cosmic-Lens All Sky Survey (CLASS) catalogue. We find only three matches ~0.87 per cent of the sample) with offsets greater than 600 milliarcsec (mas), which is considerably fewer than we would have expected from the Barrows et al. X-ray survey. We fit our histogram of offsets with a Rayleigh distribution with {sigma}=60.5mas, but find that there is an excess of objects with separations greater than ~150mas. Assuming that this excess represents AGNs with real offsets, we place an upper limit of ~17 per cent on the fraction of offset AGNs in our radio-selected sample. We select 38 objects with offsets greater than 150mas, and find they have some diverse properties: Some are well known, such as Mrk 273 and Arp 220, some have dust lanes, which may have affected the optical astrometry, and a few are strong new candidates for offset AGNs.
- ID:
- ivo://CDS.VizieR/J/A+A/433/1163
- Title:
- Spectral catalog of BeppoSAX blazars
- Short Name:
- J/A+A/433/1163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectral catalog for blazars based on the BeppoSAX archive. The sample includes 44 High-energy peaked BL Lacs (HBLs), 14 Low-energy peaked BL Lacs (LBLs), and 28 Flat Spectrum Radio Quasars (FSRQs). A total of 168 LECS, MECS, and PDS spectra were analyzed, corresponding to observations taken in the period 1996-2002. The 0.1-50keV continuum of LBLs and FSRQs is generally fitted by a single power law with Galactic column density.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/364
- Title:
- Spectral curvature values for AGN sample
- Short Name:
- J/MNRAS/471/364
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To fully understand cosmic black hole growth, we need to constrain the population of heavily obscured active galactic nuclei (AGNs) at the peak of cosmic black hole growth (z~1-3). Sources with obscuring column densities higher than 10^24^atoms/cm^2^, called Compton-thick (CT) AGNs, can be identified by excess X-ray emission at ~20-30keV, called the 'Compton hump'. We apply the recently developed Spectral Curvature (SC) method to high-redshift AGNs (2<z<5) detected with Chandra. This method parametrizes the characteristic 'Compton hump' feature cosmologically redshifted into the X-ray band at observed energies <10 keV. We find good agreement in CT AGNs found using the SC method, and bright sources fit using their full spectrum with X-ray spectroscopy. In the Chandra Deep Field-South, we measure a CT fraction of 17^+19^_-11_% (3/17) for sources with observed luminosity >5x10^43^erg/s. In the Cosmological Evolution Survey (COSMOS), we find an observed CT fraction of 15^+4^_-3_% (40/272) or 32+/-11 per cent when corrected for the survey sensitivity. When comparing to low redshift AGNs with similar X-ray luminosities, our results imply that the CT AGN fraction is consistent with having no redshift evolution. Finally, we provide SC equations that can be used to find high-redshift CT AGNs (z>1) for current (XMM-Newton) and future (eROSITA and ATHENA) X-ray missions.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/26
- Title:
- Spectral energy distributions of Roma BZCAT blazars
- Short Name:
- J/ApJS/224/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combined multi-wavelength data for blazars from the Roma-BZCAT catalog and analyzed hundreds of X-ray spectra. We present the fluxes and spectral energy distributions (SEDs), in 12 frequency bands from radio to {gamma}-rays, for a final sample of 2214 blazars. Using a model-independent statistical approach, we looked for systematic trends in the SEDs; the most significant trends involved the radio luminosities and X-ray spectral indices of the blazars. We used a principal component analysis (PCA) to determine the basis vectors of the blazar SEDs and, in order to maximize the size of the sample, imputed missing fluxes using the K-nearest neighbors method. Using more than an order of magnitude more data than was available when Fossati et al. first reported trends of SED shape with blazar luminosity, we confirmed the anti-correlation between radio luminosity and synchrotron peak frequency, although with greater scatter than was seen in the smaller sample. The same trend can be seen between bolometric luminosity and synchrotron peak frequency. Finally, we used all of the available blazar data to determine an empirical SED description that depends only on the radio luminosity at 1.4GHz and the redshift. We verified that this statistically significant relation was not a result of the luminosity-luminosity correlations that are natural in flux-limited samples (i.e., where the correlation is actually caused by the redshift rather than the luminosity).
- ID:
- ivo://CDS.VizieR/J/A+A/596/A95
- Title:
- Spectral nuclear properties of NLS1 galaxies
- Short Name:
- J/A+A/596/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is not yet well known whether narrow line Seyfert 1 (NLS1) galaxies follow the M_BH_-{sigma}_*_ relation found for normal galaxies. Emission lines, such as [SII] or [OIII]{lambda}5007, have been used as a surrogate of the stellar velocity dispersion and various results have been obtained. On the other hand, some active galactic nuclei (AGNs) have shown Balmer emission with an additional intermediate component (IC) besides the well-known narrow and broad lines. The properties of this IC have not yet been fully studied. In order to re-examine the location of NLS1 in the M_BH_-{sigma}_*_ relation, we test some emission lines, such as the narrow component (NC) of H{alpha} and the forbidden [NII]{lambda}{lambda}6548,6584 and [SII]{lambda}{lambda}6716,6731 lines, as replacements for {sigma}_*_. On the other hand, we study the properties of the IC of H{alpha} found in 14 galaxies of the sample to find a link between this component, the central engine, and the remaining lines. We also compare the emission among the broad component (BC) of H{alpha} and those emitted at the narrow line region (NLR) to detect differences in the ionizing source in each emitting region. We have obtained and studied medium-resolution spectra (170km/s FWHM at H{alpha}) of 36 NLS1 galaxies in the optical range ~5800-6800{AA}. We performed a Gaussian decomposition of the H{alpha}+[NII]{lambda}{lambda}6548,6584 profile to study the distinct components of H{alpha} and [NII] lines. We also measured the [SII] lines. We obtained black hole (BH) masses in the range log(M_{BH}_/M_{sun}_)=5.4-7.5 for our sample. We found that, in general, most of the galaxies lie below the M_BH_-{sigma}_*_ relation when the NC of H{alpha} and [NII] lines are used as a surrogate of {sigma}_*_. The objects are closer to the relation when [SII] lines are used. Nevertheless, the galaxies are still below this relation and we do not see a clear correlation between the BH masses and FWHM_[SII]_. Besides this, we found that 13 galaxies show an IC, most of which are in the velocity range ~700-1500km/s. This is same range as in AGN types and is well correlated with the FWHM of BC and, therefore, with the BH mass. On the other hand, we found that there is a correlation between the luminosity of the BC of H{alpha} and NC, IC, [NII]{lambda}6584, and [SII] lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1541
- Title:
- Spectral parameters for Mrk 335 and Ark 564
- Short Name:
- J/MNRAS/448/1541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive flux-resolved spectral analysis of the bright narrow-line Seyfert 1 AGNs, Mrk 335 and Ark 564 using observations by XMM-Newton satellite. The mean and the flux-resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low-energy soft excess and the other for the high-energy power law. A broad iron line and a couple of low-energy edges are required to explain the spectra. For Mrk 335, the 0.3-10 keV luminosity relative to the Eddington value, L_X_/L_Edd_, varied from 0.002 to 0.06. The index variation can be empirically described as {Gamma}=0.6log_10_L_X_/L_Edd_+3.0 for 0.005<L_X_/L_Edd_<0.04. At L_X_/L_Edd_~0.04 the spectral index changes and then continues to follow {Gamma}=0.6log_10_L_X_/L_Edd_+2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3-10 keV band by only a power law and an iron line. For Ark 564, the index variation can be empirically described as {Gamma}=0.2log_10_L_X_/L_Edd_+2.7 with a significantly large scatter as compared to Mrk 335. Our results indicate that for Mrk 335, there may be accretion disc geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.
- ID:
- ivo://CDS.VizieR/J/ApJ/434/54
- Title:
- Spectral properties of X-ray-selected AGNs
- Short Name:
- J/ApJ/434/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We survey the broadband spectral properties of ~500 X-ray-selected active galactic nuclei (AGNs) observed with the Einstein Observatory. Included in this survey are the ~450 AGNs in the Extended Medium Sensitivity Survey of Gioia et al. (1990ApJS...72..567G) and the ~50 AGNs in the Ultrasoft Survey of Cordova et al. (1992ApJS...81..661C). We present a revised version of the latter sample, based on the post publication discovery of a software error in the Einstein Rev-1b processing. We find that the mean spectral index of the AGNs between 0.1 and 0.6keV is softer, and the distribution of indices wider, than previous estimates based on analyses of the X-ray spectra of optically selected AGNs. A subset of these AGNs exhibit flux variability, some on timescales as short as 0.05-days. A correlation between radio and hard X-ray luminosity is confirmed, but the data do not support a correlation between the radio and soft X-ray luminosities, or between radio loudness and soft X-ray spectral slope. Evidence for physically distinct soft and hard X-ray components is found, along with the possibility of a bias in previous optically selected samples toward selection of AGNs with flatter X-ray spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A62
- Title:
- Spectra of 13 lensed quasars
- Short Name:
- J/A+A/544/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide single-epoch spectroscopic data for a sample of 13 lensed quasars. The sources have bolometric luminosities between 10^44.7-47.4^erg/s and black hole masses 10^7.6-9.8^M_{sun}. These spectra have been used to perform a systematic search for microlensing in the broad line region. The spectra have been deblended using the MCS advanced deconvolution technique. We provide the extracted and flux calibrated spectra, and the 2D deconvolved frames, separating the point-like emission from the extended emission (from the residual sky and from the lensing galaxy).