- ID:
- ivo://CDS.VizieR/J/A+A/552/A135
- Title:
- Activity of the Seyfert galaxy neighbours
- Short Name:
- J/A+A/552/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a follow-up study of a series of papers concerning the role of close interactions as a possible triggering mechanism of AGN activity. We have already studied the close (<100kpc/h) and the large-scale (<1Mpc/h) environment of a local sample of Sy1, Sy2, and bright IRAS galaxies (BIRG) and of their respective control samples. The results led us to the conclusion that a close encounter appears capable of activating a sequence where an absorption line galaxy (ALG) galaxy first becomes a starburst, then a Sy2, and finally a Sy1. Here we investigate the activity of neighbouring galaxies of different types of AGN, since both galaxies of an interacting pair should be affected. To this end we present the optical spectroscopy and X-ray imaging of 30 neighbouring galaxies around two local (z<0.034) samples of 10 Sy1 and 13 Sy2 galaxies. Although this is a pilot study of a small sample, various interesting trends have been discovered that imply physical mechanisms that may lead to different Seyfert types. Based on the optical spectroscopy we find that more than 70% of all neighbouring galaxies exhibit star forming and/or nuclear activity (namely recent star formation and/or AGN), while an additional X-ray analysis showed that this percentage might be significantly higher. Furthermore, we find a statistically significant correlation, at a 99.9% level, between the value of the neighbour's [OIII]/H{beta} ratio and the activity type of the central active galaxy, i.e. the neighbours of Sy2 galaxies are systematically more ionized than the neighbours of Sy1s. This result, in combination with trends found using the Equivalent Width of the H{alpha} emission line and the stellar population synthesis code STARLIGHT, indicate differences in the stellar mass, metallicity, and star formation history between the samples. Our results point towards a link between close galaxy interactions and activity and also provide more clues regarding the possible evolutionary sequence inferred by our previous studies.
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- ID:
- ivo://CDS.VizieR/J/ApJS/121/473
- Title:
- A diagnostic diagram for Seyfert 2 Galaxies
- Short Name:
- J/ApJS/121/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and discuss a three-dimensional diagnostic diagram for Seyfert 2 galaxies obtained using X-ray and [O III] data on a large sample of objects (reported in the Appendix). The diagram shows the K{alpha} iron line equivalent width as a function of both the column density derived from the photoelectric cutoff and the 2-10 keV flux normalized to the [O III] optical-line flux (the latter corrected for extinction and assumed to be a true indicator of the source intrinsic luminosity). We find that the hard X-ray properties of type 2 objects depend on a single parameter, the absorbing column density along the line of sight, in accordance with the unified model. The diagram can be used to identify Compton-thick sources and to isolate and study peculiar objects. From this analysis we have obtained a column density distribution of Seyfert 2 galaxies that is thought to be a good approximation of the real distribution. A large population of heavily absorbed objects is discovered, including many Compton-thick candidates. Our results indicate that the mean log N_H_cm^-2^ in type 2 Seyfert galaxies is 23.5 and that as many as 23%-30% of sources have N_H_=>10^24^cm^-2^.
- ID:
- ivo://CDS.VizieR/J/AJ/124/3465
- Title:
- AGN in the KISS-RASS sample
- Short Name:
- J/AJ/124/3465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the X-ray properties of a volume-limited sample of optically selected emission-line galaxies. The sample is derived from a correlation between the KPNO International Spectroscopic Survey (KISS), an H{alpha}-elected objective-prism survey of active galactic nuclei (AGNs) and starbursting galaxies, and the ROSAT All-Sky Survey (RASS). After elimination of all spurious matches, we identify 18 ROSAT-detected X-ray sources within the KISS sample in the 0.1-2.4keV band.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/101
- Title:
- AGN pairs from SDSS-DR7. I.
- Short Name:
- J/ApJ/737/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy mergers and close interactions have long been regarded as a viable mechanism for channeling gas toward the central supermassive black holes (SMBHs) of galaxies which are triggered as active galactic nuclei (AGNs). AGN pairs, in which the central SMBHs of a galaxy merger are both active, are expected to be common from such events. We conduct a systematic study of 1286 AGN pairs at \bar{z}~0.1 with line-of-sight velocity offsets {Delta}v<600km/s and projected separations r_p_<100h^-1^_70_kpc, selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS, Cat. II/294). This AGN pair sample was drawn from 138070 AGNs optically identified based on diagnostic emission line ratios and/or line widths. The fraction of AGN pairs with 5h^-1^_70_kpc<~r_p_<100h^-1^_70_kpc among all spectroscopically selected AGNs at 0.02<z<0.16 is 3.6% after correcting for SDSS spectroscopic incompleteness; ~30% of these pairs show morphological tidal features in their SDSS images, and the fraction becomes >~80% for pairs with the brightest nuclei.
- ID:
- ivo://CDS.VizieR/J/ApJ/639/37
- Title:
- AGN Seyfert galaxies and close neighbors
- Short Name:
- J/ApJ/639/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a three-dimensional study of the local (<=100h^-1^kpc) and the large-scale (<=1h^-1^Mpc) environment of the two main types of Seyfert AGN galaxies. For this purpose we use 48 Seyfert 1 galaxies (with redshifts in the range 0.007<=z<=0.036) and 56 Seyfert 2 galaxies (with 0.004<=z<=0.020), located at high galactic latitudes, as well as two control samples of nonactive galaxies having the same morphological, redshift, and diameter size distributions as the corresponding Seyfert samples.
- ID:
- ivo://CDS.VizieR/J/A+A/423/469
- Title:
- AGNs from RXTE 3-20keV All-Sky Survey
- Short Name:
- J/A+A/423/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compiled a sample of 95 AGNs serendipitously detected in the 3-20keV band at Galactic latitude |b|>10deg during the RXTE slew survey (XSS, Revnivtsev et al., Cat. <J/A+A/418/927>), and utilize it to study the statistical properties of the local population of AGNs, including the X-ray luminosity function and absorption distribution. We find that among low X-ray luminosity (LX<10^43.5^erg/s) AGNs, the ratio of absorbed (characterized by intrinsic absorption in the range 10^22^cm^-2^<NH<10^24^cm^-2^) and unabsorbed (NH<10^22^cm^-2^) objects is 2:1, while this ratio drops to less than 1:5 for higher luminosity AGNs. The summed X-ray output of AGNs with LX>10^41^erg/s estimated here is smaller than the earlier estimated total X-ray volume emissivity in the local Universe, suggesting that a comparable X-ray flux may be produced together by lower luminosity AGNs, non-active galaxies and clusters of galaxies. Finally, we present a sample of 35 AGN candidates, composed of unidentified XSS sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/437
- Title:
- AGNs with composite spectra. II.
- Short Name:
- J/A+AS/135/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled from the literature 88 emission-line galaxies for which the published line-ratios give indication of a "transition spectrum"; selected objects are located north of {delta}~-20{deg}, are brighter than B=17 and have z<0.1. We have observed 53 of these galaxies with the spectrograph CARELEC, attached to the OHP 1.93m telescope. The observations were carried out during several runs in May, June and July 1996 and January, March, October and November 1997. The journal of observations is given in Table 5. The spectra (R~1800) were analysed in terms of Gaussians to search for the presence of multiple line-components, coming from kinematically and spatially distinct regions - "composite spectra". The results of the fitting analysis are given in Table 6.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A113
- Title:
- A low-luminosity type-1 QSO sample. III.
- Short Name:
- J/A+A/580/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the optical spectroscopic analysis of a sample of 99 low-luminosity quasi-stellar objects (LLQSOs) at z<=0.06 base the Hamburg/ESO QSO Survey (HES). To better relate the low-redshift active galactic nucleus (AGN) to the QSO population it is important to study samples of the latter type at a level of detail similar to that of the low-redshift AGN. Powerful QSOs, however, are absent at low redshifts due to evolutionary effects and their small space density. Our understanding of the (distant) QSO population is, therefore, significantly limited by angular resolution and sensitivity. The LLQSOs presented here offer the possibility of studying the faint end of this population at smaller cosmological distances and, therefore, in greater detail. In comparing two spectroscopic methods, we aim to establish a reliable activity classification scheme of the LLQSOs sample. Our goal is to enrich our systematic multiwavelength analysis of the AGN/starburst relation in these systems and give a complementary information on this particular sample of LLQSOs from the Hamburg ESO survey. Here, we present results of the analysis of visible wavelength spectroscopy provided by the HES and the 6 Degree Field Galaxy Survey (6dFGS). These surveys use different spectroscopic techniques, long-slit and circular fiber, respectively. These allow us to assess the influence of different apertures on the activity of the LLQSOs using classical optical diagnostic diagrams. We perform a Gaussian fitting of strong optical emission lines and decompose narrow and broad Balmer components. A small number of our LLQSO present no broad component, which is likely to be present but buried in the noise. Two sources show double broad components, whereas six comply with the classic NLS1 requirements. As expected in NLR of broad line AGNs, the [SII]-based electron density values range between 100 and 1000N_e_/cm^3^. Using the optical characteristics of Populations A and B, we find that 50% of our sources with H{beta} broad emission are consistent with the radio-quiet sources definition. The remaining sources could be interpreted as low-luminosity radio-loud quasar. The BPT-based classification renders an AGN/Seyfert activity between 50 to 60%. For the remaining sources, the possible starburst contribution might control the LINER and HII classification. Finally, we discuss the aperture effect as responsible for the differences found between data sets, although variability in the BLR could play a significant role as well.
- ID:
- ivo://CDS.VizieR/III/157
- Title:
- An Ultraviolet Atlas of Quasar and Blazar Spectra
- Short Name:
- III/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This atlas contains the ultraviolet spectra of 70 quasars, blazars, and Seyfert 1 galaxies that were produced by combining over 100 low resolution spectra from the International Ultraviolet Explorer (IUE) data archive. The spectra have been extracted with an optimal algorithm (see Kinney et al. 1991) and co-added to produce spectra with the best possible signal-to-noise ratio.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/498
- Title:
- Atlas of HST STIS spectra of Seyfert galaxies
- Short Name:
- J/ApJS/166/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a compilation of spectra of 101 Seyfert galaxies obtained with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS), covering the UV and/or optical spectral range. Information on all the available spectra have been collected in a Mastertable, which is a very useful tool for anyone interested in a quick glance at the existent STIS spectra for Seyfert galaxies in the HST archive, and it can be recovered electronically. Nuclear spectra of the galaxies have been extracted in windows of 0.2" for an optimized sampling (as this is the slit width in most cases) and combined in order to improve the signal-to-noise ratio and provide the widest possible wavelength coverage. These combined spectra are also available electronically, at http://www.if.ufrgs.br/~pat/atlas.htm .
