The stability of the optical flux variation gradient for 3C120

New $B$- and $V$-band monitoring in 2014 $-$ 2015 reveals that the Seyfert 1 Galaxy, 3C120, has brightened by a magnitude of $1.4$, compared to our campaign that took place in 2009 $-$ 2010. This allowed us to check for the debated luminosity and time-dependent color variations claimed for SDSS quasars. For our 3C120 data, we find that the $B/V$ flux ratio of the variable component in the bright epoch is indistinguishable from the faint one. We do not find any color variability on different timescales ranging from about $1$ to $1800$ days. We suggest that the luminosity and time-dependent color variability is an artifact caused by analyzing the data in magnitudes instead of fluxes. The flux variation gradients of both epochs yield consistent estimates of the host galaxy contribution to our 7.5" aperture. These results confirm that the optical flux variation gradient method works well for Seyfert galaxies.Comment: 8 pages, 6 figures. Accepted for publication in section 4. Extragalactic astronomy of Astronomy and Astrophysics v2: Language-Editor Versio

Simultaneous H alpha and dust reverberation mapping of 3C120: Testing the bowl-shaped torus geometry

At the Universitaetssternwarte Bochum near Cerro Armazones we have monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 in BVRI and a narrow band filter covering the redshifted H alpha line; in addition we obtained a single con-temporary spectrum with FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a factor of three brighter, allowing us to study the shape of the broad line region (BLR) and the dust torus in a high luminosity phase. The analysis of the light curves yields that the dust echo is rather sharp and symmetric in contrast to the more complex broad H alpha BLR echo. We investigate how far this supports an optically thick bowl-shaped BLR and dust torus geometry as proposed by Kawaguchi & Mori (2010) and Goad et al. (2012). The comparison with several parameterizations of these models supports the following geometry: the BLR clouds lie inside the bowl closely above the bowl rim, up to a half covering angle 0 deg < theta < 40 deg (measured against the equatorial plane). Then the BLR is spread over many isodelay surfaces, yielding a smeared and structured echo as observed. Furthermore, if the BLR clouds shield the bottom of the bowl rim against radiation from the nucleus, the hot dust emission comes essentially from the top edge of the bowl (40 deg < theta < 45 deg). Then, for small inclinations as for 3C120, the top dust edge forms a ring which largely coincides with a narrow range of isodelay surfaces, yielding the observed sharp dust echo. The scale height of the BLR increases with radial distance from the black hole. This leads to luminosity dependent foreshortening effects of the lag. We discuss implications and possible corrections of the foreshortening for the black hole mass determination and consequences for the lag (size) - luminosity relationships and the difference to interferometric torus sizes.Comment: 17 pages, 18 figures, 3 tables, accepted for publication in in section 4. Extragalactic astronomy of Astronomy and Astrophysic

The central region of active galactic nuclei

Diese Arbeit beinhaltet drei verbundene Teilbereiche, bei denen es sich um ein techn. Projekt, eine Langzeit-Beobachtungskampagne und eine neuartige Analyse von Archivdaten handelt, welche alle auf die Erforschung der Zentralregion Aktiver Galaktischer Kerne (AGN) ausgerichtet sind. Für das VYSOS 16 Teleskop der Universitätssternwarte der Ruhr-Universität Bochum wird eine Steuerungssoftware entwickelt, die tägliche robotische Beobachtung von AGN ermöglicht. Es wurden Breit- und Schmalband-Lichtkurven für die Galaxien 3C120, ARK120, PG003+199 und ESO374-G25 aufgenommen und daraus je die Entfernung der Emissionsregionen der breiten Balmer Linien zusammen mit der mittleren nukl. Leuchtkraft bestimmt. Die Ergebnisse zeigen, dass diese neuartige Methode zuverlässig anwendbar ist. Schlussendlich wurde das bisher größte Sample von AGN mit H2O Maser Emissionen statistisch untersucht. Der Vergleich von [OIV] zu Röntgenstrahlen zeigt, dass Maser häufiger in Röntgenschwachen Quellen vorkommen.This work contains three interconnected parts, spanning an engineering project, a long term observational campaign and a novel analysis of archival data, all aimed at the research of the central region of active galactic nuclei (AGN). For the VYSOS 16 of the Universitätssternwarte der Ruhr-Universität Bochum, a software has been developed, allowing daily robotic observations of AGN. Broad- and narrow-band lightcurves have been taken of the galaxies 3C120, ARK120, PG003+199, and ESO374-G25, to calculate the average distance of the broad Balmer emission regions and the average nuclear luminosity. The results show that this novel method of photometric reverberation mapping is relieable. Finally, the largest sample of AGN with H20 maser emission has been analyzed statistically. The comparison between [OIV] and X-Rays reveals that Maser are found predominantly in X-Ray absorbed sources