Ministerio de Economía y Competitividad Gobierno de Canarias Universidad de La Laguna CSIC Centro de Excelencia Severo Ochoa

Results Gallery

Select a year: 2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 |

· More scientific highlights from this year.

The central molecular gas structure in LINERs with low luminosity AGN: evidence for gradual disappearance of the torus.

Author/s: F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, M. Elitzur

Reference: IN PRESS

<em>K</em><strong>-</strong>band nuclear spectra of LLAGN extracted from our SINFONI data in <em>r</em> = 0.3” apertures. The prominent emission lines are from H<sub>2</sub> (marked at the top of the figure), the strongest being 1-0 S(1) at 2.12 <em>μ</em>m. Several stellar absorption features (like the <sup>12</sup>CO bandheads or NaI), characteristic of evolved stellar populations, are also noticeable. All <em>K</em>-band ionization lines (including Brγ) are absent in these objects. A similar spectrum is observed in NGC 1097, but Brγ is marginally detected (Davies et al. 2007). Since Brγ is normally considered a tracer of young stars, the marginally/non-detection of this line indicates little to no on-going star formation. In NGC 1097 the weak Brγ flux is consistent with a very young (<strong><</strong> 10 Myr) compact (<strong><</strong> 9 pc) episode of star formation, which we consider as little on-going star formation.
K-band nuclear spectra of LLAGN extracted from our SINFONI data in r = 0.3” apertures. The prominent emission lines are from H2 (marked at the top of the figure), the strongest being 1-0 S(1) at 2.12 μm. Several stellar absorption features (like the 12CO bandheads or NaI), characteristic of evolved stellar populations, are also noticeable. All K-band ionization lines (including Brγ) are absent in these objects. A similar spectrum is observed in NGC 1097, but Brγ is marginally detected (Davies et al. 2007). Since Brγ is normally considered a tracer of young stars, the marginally/non-detection of this line indicates little to no on-going star formation. In NGC 1097 the weak Brγ flux is consistent with a very young (< 10 Myr) compact (< 9 pc) episode of star formation, which we consider as little on-going star formation.

We present observations of the molecular gas in the nuclear environment of three prototypical low luminosity AGN (LLAGN), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H2 1-0 S(1) emission at angular resolutions of ~0.17”. On scales of 50-150 pc the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/ σ < 1 and NH> 1023 cm-2) that is likely to be associated with the outer extentof any smaller scale obscuring structure. In contrast to Seyfert galaxies, the molecular gas in LLAGN has a V/ σ < 1 over an area that is ~9 times smaller and column densities that are in average ~3 times smaller. We interpret these results as evidence for a gradual disappearance of the nuclear obscuring structure. While a disk wind may not be able to maintain a thick rotating structure at these luminosities, inflow of material into the nuclear region could provide sufficient energy to sustain it. In this context, LLAGN may represent the final phase of accretion in current theories of torus evolution. While the inflow rate is significant during the Seyfert phase, it is slowly decreasing, and the collisional disk is gradually transitioning to become geometrically thin. Furthermore, the nuclear region of these LLAGN is dominated by intermediate-age/old stellar populations (with little or no on-going star formation), consistent with a late stage of evolution.

We use our own cookies and cookies from a third party to gather statistical information to improve our services and our website. If you continue with the navigation, you are accepting the installation and use of these cookies. You can change the configuration of your browser not to accept the installation or you can obtain more information in our Cookie Policy.

OK