The Supermassive Black Hole and Double Nucleus of the Core Elliptical NGC 5419

We obtained adaptive-optics assisted SINFONI observations of the central regions of the giant elliptical galaxy NGC5419 with a spatial resolution of 0.2 arcsec (≈55 pc). NGC5419 has a large depleted stellar core with a radius of 1.58 arcsec (430 pc). HST and SINFONI images show a point source located at the galaxy\u27s photocentre, which is likely associated with the low-luminosity AGN previously detected in NGC5419. Both the HST and SINFONI images also show a second nucleus, off-centred by 0.25 arcsec (≈70 pc). Outside of the central double nucleus, we measure an almost constant velocity dispersion of σ∼350 km/s. In the region where the double nucleus is located, the dispersion rises steeply to a peak value of ∼420 km/s. In addition to the SINFONI data, we also obtained stellar kinematics at larger radii from the South African Large Telescope. While NGC5419 shows low rotation (v\u3c50 km/s), the central regions (inside ∼4rb) clearly rotate in the opposite direction to the galaxy\u27s outer parts. We use orbit-based dynamical models to measure the black hole mass of NGC5419 from the kinematical data outside of the double nuclear structure. The models imply MBH=7.2+2.7−1.9×109 M⊙. The enhanced velocity dispersion in the region of the double nucleus suggests that NGC5419 possibly hosts two supermassive black holes at its centre, separated by only ≈70 pc. Yet our measured MBH is consistent with the black hole mass expected from the size of the galaxy\u27s depleted stellar core. This suggests, that systematic uncertainties in MBH related to the secondary nucleus are small

Demystifying the coronal line region of active galactic nuclei: spatially resolved spectroscopy with HST

We present an analysis of STIS/HST optical spectra of a sample of ten Seyfert galaxies aimed at studying the structure and physical properties of the coronal-line region (CLR). The high-spatial resolution provided by STIS allowed us to resolve the CLR and obtain key information about the kinematics of the coronal-line gas, measure directly its spatial scale, and study the mechanisms that drive the high-ionisation lines. We find CLRs extending from just a few parsecs (~10 pc) up to 230 pc in radius, consistent with the bulk of the coronal lines (CLs) originating between the BLR and NLR, and extending into the NLR in the case of [FeVII] and [NeV] lines. The CL profiles strongly vary with the distance to the nucleus. We observed line splitting in the core of some of the galaxies. Line peak shifts, both red- and blue-shifts, typically reached 500 km/s, and even higher velocities (1000 km/s) in some of the galaxies. In general, CLs follow the same pattern of rotation curves as low-ionisation lines like [OIII]. From a direct comparison between the radio and the CL emission we find that neither the strength nor the kinematics of the CLs scale in any obvious and strong way with the radio jets. Moreover, the similarity of the flux distributions and kinematics of the CLs and low-ionisation lines, the low temperatures derived for the gas, and the success of photoionisation models to reproduce, within a factor of few, the observed line ratios, point towards photoionisation as the main driving mechanism of CLs.Comment: Accepted for publication in MNRAS. 27 pages, 21 figures, 4 table

Los pársecs más internos de las galaxias activas /

Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2010.Los núcleos activos de galaxias o AGNs son considerados los objetos más luminosos del Universo. Estos emiten cantidades importantes de energía a lo largo de todo el espectro electromagnético, la cual es capaz de superar por varios órdenes de magnitud a la liberada por el resto de la galaxia. Se cree que esta energía es producida por material ubicado en un disco de acreción alrededor de un agujero negro supermasivo central. Gran parte de la investigación sobre estos objetos llevada a cabo en las últimas tres décadas está dedicada al entendimiento de la fuente central y sus efectos en el gas que la rodea. Con el objetivo de contribuir a estos estudios, en esta Tesis se analizaron las componentes más internas de galaxias activas cercanas a partir del estudio de la emisión continua y de las líneas coronales. La región donde son emitidas estas últimas es la más cercana a la fuente central que puede ser resuelta con los instrumentos ópticos e infrarrojos actuales y, por lo tanto, proveen información sobre los procesos energéticos que ocurren en el centro de los AGNs.Galaxias activas -- La región de líneas coronales en AGNs -- Una mirada con el telescopio espacial Hubble -- Una visión 3D de la región de líneas coronales de NGC1068 -- La emisión continua de la galaxia activa Mrk 1239 -- Comentarios finales.Fil: Mazzalay, Ximena. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina

The complexity of the coronal line region in AGNs: Gas-jet interactions and outflows revealed by NIR spectroscopy

Apart from the classical broad line region (BLR) at small core distances, and the extended classical narrow-line region (NLR), a subset of active galactic nuclei (AGN) show, in their spectra, lines from very highly ionised atoms, known as Coronal lines (CLs). The precise nature and origin of these CLs remain uncertain. Advances on this matter include the determination of the size and morphology of the CLR by means of optical HST and ground-based AO imaging/spectroscopy in a few AGNs. The results indicate CLRs with sizes varying from compact (~30 pc) to extended (~200 pc) emission and aligned preferentially with the direction of the lower ionisation cones seen in these sources. In this talk, we present results of a pioneering work aimed at studying the CLR in the near-infrared region on a selected sample of nearby AGNs. The excellent angular resolution of the data allowed us to resolve and map the extension of the coronal line gas and compare it to that emitting low- and mid-ionization lines. In most cases, the very good match between the radio emission and the CLR suggest that at least part of the high-ionization gas is jet-driven. Results from photoionization models where the central engine is the only source of energy input strongly fail at reproducing the observed line ratios, mainly at distances larger than 60 pc from the centre. We discuss here other processes that should be at work to enhance this energetic emission and suggest that the presence of coronal lines in AGNs is an unambiguous signature of feedback processes in these sources