arXiv subjects

W. Kollatschny

Publications and source records attributed to W. Kollatschny.

At least 55 records · Page 3Linked to original sources

arXiv2012

The shape of broad-line profiles in AGN

We present a study of the broad optical/UV emission line profiles in AGN (active galactic nuclei) to get information on the dominant velocity components (turbulence, rotation, etc.) in the central broad-line region (BLR). We introduce line broadening simulations of emission line profiles and compare these results with the largest homogeneous data set of reverberation-mapped AGN. The underlying broad-line profiles in AGN are Lorentzian profiles caused by turbulence in the line emitting region. The turbulent velocities are different for the different line emitting regions of Ha, Hg, Lya, CIII] 1909, He II 1640, and Si IV 1400. The turbulent velocities go from 400 km/s for Hb up to 3,800 km/s for Lya+Nv 1240. The dominating broadening mechanism of these profiles is broadening due to rotation. The rotation velocities causing the line profile broadening go from 500 km/s up to 6,500 km/s. Here we present interrelations between observed emission line widths (FWHM) and their related rotational velocities to correct for the contribution of the turbulence to the broad-line profiles.

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arXiv2012

The environment of AGNs and the activity degree of their surrounding galaxies

Aims. We present results of a comprehensive spectral study on the large-scale environment of AGNs based on Sloan Spectroscopic Survey data. Methods. We analyzed the spectra of galaxies in the environment of AGN and other activity classes up to distances of 1 Mpc. Results. The mean Hα and [OIII] λ5007 line luminosities in the environmental galaxies within a projected radius of 1 Mpc are highest around Seyfert 1 galaxies, with decreasing luminosities for Seyfert 2 and HII galaxies, and lowest for absorption line galaxies. Furthermore, there is a trend toward Hα and [OIII] luminosities in the environmental galaxies increasing as a function of proximity to the central emission line galaxies. There is another clear trend toward a neighborhood effect within a radius of 1000 kpc for the AGN and non-AGN types: Seyfert galaxies tend to have the highest probability of having another Seyfert galaxy in the neighborhood. HII galaxies tend to have the highest probability of having another HII galaxy in the neighborhood, etc. The number of companions within 1000 kpc is inversely correlated with the Hα, [OIII] λ5007, as well as with the continuum luminosities of the central galaxies, regardless of whether they are of Seyfert, HII, or absorption line types.

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arXiv2012

The Infrared Ca II lines in Sunspot Umbrae

We present an empirical working model for sunspot umbrae which equally describes observed continuum intensities and line profiles. The wings of the infrared Ca II lines depend sensitively on the temperature gradient at -0.6 < log(tau-0.5) < +0.3 but not essentially on the absolute value of T. These lines are observed to remain almost unchanged from photosphere to umbra and are thus insensitive to parasitic light. It is also shown that the infrared K I 7699 line is suitable for umbral spectroscopy since it is not seriously blended, its continuum is well defined and it is less influenced by parasitic light as compared to lines in the visible spectrum, due to the smaller umbral contrast. Calculations show that the umbral gradient dT/d(tau), required to fit the Ca II triplet lines, strongly conflicts with the observed profiles of K I 7699, NaD2 and Fe I 5434 (g=0), even when assuming vanishing Fe II lines for a maximum correction of parasitic light. It is shown that this discrepancy from the different line profiles may be removed by adopting an opacity enhancement as introduced by Zwaan (1974) from a discussion of continuum contrasts alone. The finally proposed umbral working model is very close to a scaled model of the quiet sun with T(eff)= 4000 K thus resembling a M0 rather than a K5 stellar atmosphere

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arXiv2012

Spectral Optical Monitoring of the Narrow Line Seyfert 1 galaxy Ark 564

We present the results of a long-term (1999--2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow line Seyfert 1 (NLS1) galaxies, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted Ha, Hb, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the Hb and Fe II lines with a sum of Gaussian components. We found that during the monitoring period the spectral variation (F_max/F_min) of Ark 564 was between 1.5 for Ha to 1.8 for the Fe II lines. The correlation between the Fe II and Hb flux variations is of higher significance than that of Ha and Hb (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like, and did not change shape during the monitoring period. We investigated, in detail, the optical Fe II emission and found different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad line emission region.

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arXiv2011

Spectral optical monitoring of 3C 390.3 in 1995-2007: II. Variability of the spectral line parameters

A study of the variability of the broad emission-line parameters of 3C390.3, an active galaxy with the double-peaked emission-line profiles, is presented. We give a detail analysis of variation in the broad Ha and Hb profiles, the ratios, and the Balmer decrement of different line segments. Studying the variability of the line profiles we explore the disk structure, that is assumed to emit the broad double-peaked Ha and Hb emission lines. We divided the observed spectra in two periods (before and after the outburst in 2002) and analyzed separately the variation in these two periods. First we analyzed the spectral emission-line profiles of Ha and Hb, measuring the peak positions. Then, we divided lines into several segments, and we measured the line-segment fluxes. The Balmer decrement variation for total Ha and Hb fluxes, as well as for the line segments has been investigated and discussed. We modeled the line parameters variation using an accretion disk model. We compared the variability in the observed line parameters with the disk model predictions and found that the variation in line profiles and in line segments corresponds to the emission of a disk-like BLR. But, also there is probably one additional emission component that contributes to the Ha and Hb line center. We found that the variation in the line profiles is caused by the variation in the parameters of the disk-like BLR, first of all in the inner (outer) radius which can well explain the line parameter variations in the Period I. The Balmer decrement across the line profile has a bell-like shape, and it is affected not only by physical processes in the disk, but also by different emitting disk dimension of the Ha and Hb line. The geometry of the BLR of 3C390.3 seems to be very complex, and inflows/outflows might be present, but it is evident that the broad line region with disk-like geometry has dominant emission.

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arXiv2010

Line profile and continuum variability in the very broad-line Seyfert galaxy Mrk 926

We present results of an intensive spectroscopic variability campaign of the very broad-line Seyfert 1 galaxy Mrk 926. Our aim is to investigate the broad-line region (BLR) by studying the intensity and line profile variations of this galaxy on short timescales. High signal-to-noise ratio(S/N) spectra were taken with the 9.2m Hobby-Eberly Telescope (HET) in identical conditions during two observing campaigns in 2004 and 2005. After the spectral reduction and internal calibration we achieved a relative flux accuracy of better than 1%. The rms profiles of the very broad Balmer lines have shapes that differ from their mean line profiles, consisting of two inner (v $\lesssim \pm{}$ 6000 km s$^{-1}$) and two outer (v $\gtrsim \pm{}$ 6000 km s$^{-1}$) line components in addition to a central component (v $\lesssim \pm{}$ 600 km s$^{-1}$). These outer and inner line segments varied with different amplitudes during our campaign. The radius of the BLR is very small with an upper limit of 2 light-days for the H$β$ BLR size. We derived an upper limit to the central black hole mass of $ M= 11.2 \times 10^{7} M_{\odot} $. The 2-D cross-correlation functions CCF($τ$,$v$) of H$β$ and H$α$ are flat within the error limits. The response of the Balmer line segments with respect to continuum variations is different in the outer and inner wings of H$α$ and H$β$. This double structure in the response curves - of two separate inner and outer components - has also been seen in the rms line profiles. We conclude that the outer and inner line segments originate in different regions and/or under different physical conditions.

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arXiv2009

First-year Sloan Digital Sky Survey-II (SDSS-II) Supernova Results: Hubble Diagram and Cosmological Parameters

We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey, the Hubble Space Telescope, and a compilation of nearby SN Ia measurements. Combining the SN Hubble diagram with measurements of Baryon Acoustic Oscillations from the SDSS Luminous Red Galaxy sample and with CMB temperature anisotropy measurements from WMAP, we estimate the cosmological parameters w and Omega_M, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = -0.76 +- 0.07(stat) +- 0.11(syst), Omega_M = 0.306 +- 0.019(stat) +- 0.023(syst) using MLCS2k2 and w = -0.96 +- 0.06(stat) +- 0.12(syst), Omega_M = 0.265 +- 0.016(stat) +- 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST supernovae. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame $U$-band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (beta). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties.

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arXiv2008

New active galactic nuclei detected in ROSAT All Sky Survey galaxies - The complete dataset

The ROSAT ALL Sky Survey Bright Source Catalogue (RASS-BSC) has been correlated with the Catalogue of Principal Galaxies (PGC) to identify new extragalactic counterparts. 550 reliable optical counterparts have been detected. We took optical spectra of 176 X-ray candidates and companions at ESO, Calar Alto observatory and McDonald observatory. We discuss the redshift-, linewidth-, as well as optical and X-ray luminosity distribution of our ROSAT selected sample. 139 galaxies of our 166 X-ray counterparts have been identified as AGN with 93 being Seyfert 1 galaxies (61%). Eighteen of them (20%) are Narrow Line Seyfert 1 galaxies. 34 X-ray candidates (21%) are LINERs and only eight candidates (5%) are Seyfert 2. The ratio of the number of Seyfert 1 galaxies to Seyfert 2 galaxies is about 11/1. Optical surveys result in ratios of 1/1.4. The high fraction of detected Seyfert 1 galaxies is explained by the sensitivity of the ROSAT to soft X-rays which are heavily absorbed in type 2 AGN. Two X-ray candidates are HII-galaxies and 25 candidates (15%) show no signs of spectral activity. The AGN in our RASS selected sample exhibit slightly higher optical luminosities M_B = (-20.71 +- 1.75) mag and similar X-ray luminosities (log(L_X [erg/s]) = 42.9 +- 1.7) compared to other AGN surveys. The Halpha line width distribution (FWHM) of our newly identified ROSAT AGN sample is similar to the line widths distribution based on SDSS AGN. However, our newly identified RASS AGN have rather reddish colors explaining why they have not been detected before in ultraviolet or blue excess surveys.

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arXiv2007

The optical emission line spectrum of Mark 110

We analyse in detail the rich emission line spectrum of Mark 110 to determine the physical conditions in the nucleus of this object, a peculiar NLS1 without any detectable Fe II emission associated with the broad line region and with a $\lambda5007/Hβ$ line ratio unusually large for a NLS1. We use 24 spectra obtained with the Marcario Low Resolution Spectrograph attached at the prime focus of the 9.2 m Hobby-Eberly telescope at the McDonald observatory. We fitted the spectrum by identifying all the emission lines (about 220) detected in the wavelength range 4200-6900 Å(at rest). The narrow emission lines are probably produced in a region with a density gradient in the range 10$^{3}-10^{6}$ cm$^{-3}$ with a rather high column density (5$\times10^{21}$ cm$^{-2}$). In addition to a narrow line system, three major broad line systems with different line velocity and width are required. We confirm the absence of broad Fe II emission lines. We speculate that Mark 110 is in fact a BLS1 with relatively "narrow" broad lines but with a BH mass large enough compared to its luminosity to have a lower than Eddington luminosity.

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arXiv2007

The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary

The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5 degrees wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for discovery of new objects. Supernova imaging observations are being acquired between 1 September and 30 November of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.

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arXiv2006

XMM-Newton observation of Mrk 110

We report on the first XMM-Newton observation of the bright Narrow-Line Seyfert 1 galaxy Mrk 110. We find a narrow Fe K fluorescent line, a broad component FWHM ~ 16500 km/s of the OVII triplet, either due to infall motions or gravitational redshift effects in the vicinity of the central black hole, a Comptonized accretion disc layer, and a strong starburst component. If the broad redshifted soft X-ray components are due to gravitational redshift effects, the distance of the line emitting regions ranges between about 0.2 and 1 light day with respect to the central black hole.

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arXiv2006

Probing unexplored territories with MUSE: a second generation instrument for the VLT

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin**2 sampled at 0.2x0.2 arcsec**2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 465-930 nm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec**2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 600-930 nm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.

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arXiv2006

Spectral line variability amplitudes in AGNs

We present the results of a long-term variability campaign of very broad-line AGNs with line widths broader than FWHM $>$ 5000 kms$^{-1}$. The main goal of our investigation was to study whether the widths of the optical broad emission lines are correlated with the optical intensity variations on timescales of years. Our AGN sample consisted of 10 objects. We detected a significant correlation between optical continuum variability amplitudes and H$β$ emission line widths (FWHM) and, to a lesser degree, between H$β$ line intensity variations and H$β$ equivalent widths. We add the spectroscopic data of variable AGNs from the literature to supplement our sample. The AGNs from other optical variability campaigns with different line-widths helped to improve the statistical significance of our very broad-line AGN sample. After including the data on 35 additional galaxies, the correlation between optical continuum variability amplitudes and H$β$ emission line widths becomes even more significant and the probability that this is a random correlation drops to 0.7 percent.

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arXiv2003

Spin orientation of supermassive black holes in active galaxies

Accretion of gas onto a central supermassive black hole is generally accepted to be the source of the emitted energy in active galactic nuclei.The broad emission lines we observe in their optical spectra are probably formed in the wind of an accretion disk at distances of light days to light years from the central black hole. The variable fraction of the emission lines originates at typical distances of only 1 to 50 light days from the central supermassive black hole. We derived a central black hole mass of M_orbital = 1.8 +/-0.4 x 10^7 M_sun in the Seyfert galaxy Mrk110 assuming the broad emission lines are generated in gas clouds orbiting within an accretion disk. This figure depends on the inclination angle of the accretion disk. Here we report on the detection of gravitational redshifted emission in the variable fraction of the broad emission lines. We derive a central black hole mass of M_grav = 14.0 +/-3.0 x 10^7 M_sun. These measurements are independent on the orientation of the accretion disk. The comparison of both black hole mass estimates allows to determine the projection of the central accretion disk angle i to 21 +/-5 deg. in Mrk110 and therefore the orientation of the spin axis of the central black hole.

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arXiv2003

Accretion disk wind in the AGN broad-line region: Spectroscopically resolved line profile variations in Mrk110

Detailed line profile variability studies of the narrow line Seyfert 1 galaxy Mrk110 are presented. We obtained the spectra in a variability campaign carried out with the 9.2m Hobby-Eberly Telescope at McDonald Observatory. The integrated Balmer and Helium (HeI,II) emission lines are delayed by 3 to 33 light days to the optical continuum variations respectively. The outer wings of the line profiles respond much faster to continuum variations than the central regions. The comparison of the observed profile variations with model calculations of different velocity fields indicates an accretion disk structure of the broad line emitting region in Mrk110. Comparing the velocity-delay maps of the different emission lines among each other a clear radial stratification in the BLR can be recognized. Furthermore, delays of the red line wings are slightly shorter than those of the blue wings. This indicates an accretion disk wind in the BLR of Mrk110. We determine a central black hole mass of M = $1.8\cdot10^{7} M_{\odot}$. Because of the poorly known inclination angle of the accretion disk this is a lower limit only.

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arXiv2002

Geometry and Kinematics in the Central Broad-Line Region of a Seyfert 1 Galaxy

We recorded spectra of the highly variable Seyfert 1 galaxy Mrk110 in a variability campaign with the 9.2m Hobby-Eberly Telescope at McDonald Observatory in order to study the detailed line profile variations of the broad emission lines. Here we show that only an AGN model predicting the formation of the broad Hb line emission in the wind of an accretion disk matches the observed 2-D variability pattern. Furthermore, we derive an improved mass of the central supermassive black hole of M = 1.0(+1.0,-0.5)E7 M_sun from the Hb velocity-delay map.

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arXiv2001

Short-term emission line and continuum variations in Mrk110

We present results of a variability campaign of Mrk110 performed with the 9.2-m Hobby-Eberly Telescope (HET) at McDonald Observatory. The high S/N spectra cover most of the optical range. They were taken from 1999 November through 2000 May. The average interval between the observations was 7.3 days and the median interval was only 3.0 days. Mrk110 is a narrow-line Seyfert 1 galaxy. During our campaign the continuum flux was in a historically low stage. Considering the delays of the emission lines with respect to the continuum variations we could verify an ionization stratification of the BLR. We derived virial masses of the central black hole from the radial distances of the different emission lines and from their widths. The calculated central masses agree within 20%. Furthermore, we identified optical HeI singlet emission lines emitted in the broad-line region. The observed line fluxes agree with theoretical predictions. We show that a broad wing on the red side of the [OIII]5007 line is caused by the HeI singlet line at 5016A.

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arXiv1999

Strong optical line variability in Mkn 110

We present results of a long-term variability campaign on the Seyfert 1 galaxy Markarian 110. Mkn 110 is a narrow-line Seyfert 1 object hosted in a morphological peculiar galaxy. We monitored the optical continuum and the line intensities as well as their profiles over a time interval of nearly ten years. The continuum and the Balmer lines varied by a factor of 2 to 5 within two years. The HeII4686 line showed exceptional intensity variations of a factor of eight. We detected an additional independent very broad-line region in high intensity stages of the Balmer and HeII lines. The CCF analysis of the HeII line indicates that this very broad-line region originates at a distance of 9 light days only from the central ionizing source.

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