- ID:
- ivo://CDS.VizieR/J/MNRAS/434/336
- Title:
- Nuclear activity in isolated galaxies
- Short Name:
- J/MNRAS/434/336
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic study of the incidence of active galactic nucleus (AGN) nuclear activity in two samples of isolated galaxies. Our results show that the incidence of non-thermal nuclear activity is about 43 and 31 percent for galaxies with emission lines and 40 and 27 percent for the total sample, respectively. For the first time we have a large number of bona fide isolated galaxies (513 objects), with statistically significant number of all morphological types. A large fraction (~70%) of elliptical galaxies or early-type spirals have an AGN and ~70% of them are low-ionization nuclear emission-line regions. We find a larger fraction of AGN in early morphological types, as also found in the general population of galaxies. Only 3% of the AGN show the presence of broad lines (not a single one can be classified as type 1 AGN). This is an important result which is at odds with the unified model even if we consider warped or clumpy tori. Finally, we interpret the large fraction of AGN in isolated galaxies as the result of secular accretion.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/2505
- Title:
- Nuclear activity in ULIRGs
- Short Name:
- J/MNRAS/405/2505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 5-8um spectral analysis performed on the largest sample of local ultraluminous infrared galaxies (ULIRGs) selected so far, consisting of 164 objects up to a redshift of ~0.35. The unprecedented sensitivity of the Infrared Spectrograph onboard Spitzer allowed us to develop an effective diagnostic method to quantify the active galactic nucleus (AGN) and starburst (SB) contribution to this class of objects. The large AGN over SB brightness ratio at 5-8um and the sharp difference between the spectral properties of AGN and SB galaxies in this wavelength range make it possible to detect even faint or obscured nuclear activity, and disentangle its emission from that of star formation. By defining a simple model we are also able to estimate the intrinsic bolometric corrections for both the AGN and SB components, and obtain the relative AGN/SB contribution to the total luminosity of each source.
- ID:
- ivo://CDS.VizieR/J/PAZh/27/942
- Title:
- Nuclear activity of NGC 5548
- Short Name:
- J/PAZh/27/942
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVRI observations of the nucleus of the Seyfert galaxy NGC 5548 from 1990 until 2000 at four astronomical observatories are given in Table2. All data have been reduced to a single system and are given for an A=14.3" aperture.
- ID:
- ivo://CDS.VizieR/J/PAZh/27/83
- Title:
- Nuclear activity of NGC 4151 in 1989-2000
- Short Name:
- J/PAZh/27/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broadband UBVRI observations of the nucleus of the Seyfert galaxy NGC 4151 from 1989 until 2000 at three astronomical observatories: the Crimean Station of the Sternberg astronomical institute, The Special Astronomical observatory in the Caucasus and the Maidanac observatory of the Ulugbek Astronomical institute in Uzbekistan. All data have been reduced to a single system and are given for an A=27.5" aperture.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A74
- Title:
- Nuclear obscuration in LINERs
- Short Name:
- J/A+A/578/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most of the optically classified low-ionisation, narrow emission-line regions (LINERs) nuclei host an active galactic nucleus (AGN). However, how they fit into the unified model (UM) of AGN is still an open question. The aims of this work are to study at mid-infrared (mid-IR) (1) the Compton-thick nature of LINERs (i.e. hydrogen column densities of N_H_>1.5x10^24^cm^-2^) and (2) the disappearance of the dusty torus in LINERs predicted from theoretical arguments. We have compiled all the available low spectral-resolution, mid-IR spectra of LINERs from the InfraRed Spectrograph (IRS) onboard Spitzer. The sample contains 40 LINERs. We have complemented the LINER sample with Spitzer/IRS spectra of PGQSOs, Type-1 Seyferts (S1s), Type-2 Seyferts (S2s), and StarBurst (SB) nuclei. We studied the AGN compared to the starburst content in our sample using different indicators: the equivalent width of the polycyclic aromatic hydrocarbon at 6.2{mu}m, the strength of the silicate feature at 9.7{mu}m, and the steepness of the mid-IR spectra. We classified the spectra as SB-dominated and AGN-dominated, according to these diagnostics and compared the average mid-IR spectra of the various classes. Moreover, we studied the correlation between the 12{mu}m luminosity, {nu}L_{nu}_(12{mu}m), and the 2-10keV energy band X-ray luminosity, L_X_(2-10keV).
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/3570
- Title:
- Nuclear star clusters in 228 spiral galaxies
- Short Name:
- J/MNRAS/441/3570
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of photometric and structural properties of 228 nuclear star clusters (NSCs) in nearby late-type disc galaxies. These new measurements are derived from a homogeneous analysis of all suitable Wide Field Planetary Camera 2 (WFPC2) images in the Hubble Space Telescope (HST) archive. The luminosity and size of each NSC are derived from an iterative point spread function (PSF) fitting technique, which adapts the fitting area to the effective radius (r_eff_) of the NSC and uses a WFPC2-specific PSF model tailored to the position of each NSC on the detector. The luminosities of NSCs are <=10^8^L_V,{sun}_, and their integrated optical colours suggest a wide spread in age. We confirm that most NSCs have sizes similar to globular clusters (GCs), but find that the largest and brightest NSCs occupy the regime between ultra-compact dwarf (UCD) and the nuclei of early-type galaxies in the size-luminosity plane. The overlap in size, mass, and colour between the different incarnations of compact stellar systems provides a support for the notion that at least some UCDs and the most massive Galactic GCs may be remnant nuclei of disrupted disc galaxies. We find tentative evidence for the NSCs' r_eff_ to be smaller when measured in bluer filters and discuss possible implications of this result. We also highlight a few examples of complex nuclear morphologies, including double nuclei, extended stellar structures, and nuclear F606W excess from either recent (circum-)nuclear star formation and/or a weak active galactic nucleus. Such examples may serve as case studies for ongoing NSC evolution via the two main suggested mechanisms, namely cluster merging and in situ star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/2122
- Title:
- Nuclear star clusters photometric masses
- Short Name:
- J/MNRAS/457/2122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic nuclei typically host either a nuclear star cluster (NSC, prevalent in galaxies with masses <~10^10^M_{sun}_) or a massive black hole (MBH, common in galaxies with masses >~10^12^M_{sun}_). In the intermediate-mass range, some nuclei host both an NSC and an MBH. In this paper, we explore scaling relations between NSC mass (M_*,gal_) and host-galaxy total stellar mass (M_NSC_) using a large sample of NSCs in late- and early-type galaxies, including a number of NSCs harbouring an MBH. Such scaling relations reflect the underlying physical mechanisms driving the formation and (co)evolution of these central massive objects. We find ~1.5{sigma} significant differences between NSCs in late- and early-type galaxies in the slopes and offsets of the relations r_eff,NSC_-M_NSC_, r_eff,NSC_-M_*,gal_ and M_NSC_-M_*,gal_, in the sense that (i) NSCs in late types are more compact at fixed M_NSC_ and M_*,gal_; and (ii) the M_NSC_-M_*,gal_ relation is shallower for NSCs in late types than in early types, similar to the M_BH-M_*,bulge relation. We discuss these results in the context of the (possibly ongoing) evolution of NSCs, depending on host-galaxy type. For NSCs with an MBH, we illustrate the possible influence of an MBH on its host NSC, by considering the ratio between the radius of the MBH sphere of influence and r_eff,NSC_. NSCs harbouring a sufficiently massive black hole are likely to exhibit surface brightness profile deviating from a typical King profile.
- ID:
- ivo://CDS.VizieR/J/MNRAS/363/1019
- Title:
- Nucleated dwarf ellipticals in Virgo cluster
- Short Name:
- J/MNRAS/363/1019
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using images from a charge-coupled device survey with the Wide Field Camera on the Isaac Newton Telescope, we performed B- and I-band photometry on 156 Virgo cluster dwarf elliptical (dE) galaxies, 25 candidate new cluster dwarfs, and nine candidate field dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/439/487
- Title:
- Nuker law fits of radio galaxies
- Short Name:
- J/A+A/439/487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Nuker law fits of brightness profiles of a number of radio galaxies that were observed with the HST. The data on B2 radio galaxies were described in Capetti et al. (2000A&A...362..871C), while a number of 3C galaxies with FR II radio structure were taken from the HST archive. The profiles are compared with other samples of early type galaxies, taken from the literature. We find that radio galaxies always have "core"-type profiles, i.e. a shallow profile in the inner part of the galaxy, while radio-quiescent ellipticals may either have "core"-type or "power-law" type profiles.
- ID:
- ivo://CDS.VizieR/J/ApJ/664/226
- Title:
- Nuker law parameters of early-type galaxies
- Short Name:
- J/ApJ/664/226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine several HST investigations on the central structure of early-type galaxies to generate a large sample of surface photometry. The studies selected were those that used the "Nuker law" to characterize the inner light distributions of the galaxies. The sample comprises WFPC1 and WFPC2 V-band observations published earlier by our group, R-band WFPC2 photometry of Rest et al. (2001AJ....121.2431R), NICMOS H-band photometry by Ravindranath et al. (2001AJ....122..653R) and Quillen et al. (2000ApJS..128...85Q), and the brightest cluster galaxy WFPC2 I-band photometry of Laine et al. (2003, Cat. J/AJ/125/478).