Prague Relativistic Astrophysics

Lydia Moser

In my talk I will give a short insight into my recent work which can be divided into two research topics related to black holes, i.e. active galactic nuclei (AGN) and the Galactic Center.

The strong correlation between the black hole mass and the central velocity dispersion of galaxies suggests a coeval growth of supermassive black holes (SMBH) and the surrounding stellar bulges. The growth is believed to be regulated by an interplay of a nuclear fueling, i.e. inflow of gas which is then consumed by star formation and accretion onto the SMBH, and a feedback from these regions such as winds, outflows and radiation. The diverse mechanisms that might be involved in these processes (e.g. galactic interactions or secular processes) are topics of current research. Going down to smaller scales little is known about the interaction of the SMBH with its immediate environment. Our own Galactic Center offers us a unique laboratory to study the physics around the SMBH, Sagittarius A*, on sub-parsec scales.

In the first part of my talk I present interferometric observations of three barred galaxies from our Borderline Type 1 QSO (B1Q) sample with the Submillimeter Array (SMA) in the CO(2-1) and (3-2) line transition. The goal of the sample is to investigate the nuclear fueling in type-1 active galactic nuclei (AGN) with magnitudes around the classical Seyfert/Quasi-Stellar Object (QSO) demarcation, all located in the volume 0.01 < z < 0.06. We intend to study the evolutionary link between the local population and the more active galaxies at higher redshifts. As preliminary result we find that all three galaxies are rich in molecular gas with masses ranging from 1.3—11 x 10^9 M_sun, and two of them can be classified as luminous infrared galaxies (LIRGs) indicating high star formation activity. The region of CO emission is very compact, i.e. FWHM < 1.7 kpc, and only in one case the molecular gas also extends along the galactic bar. From the two galaxies with a compact CO emission region, one shows signatures of an inflow. The continuum flux is not detected which is consistent with an expected dust contribution of less than 50 muJy.

The second part is about radio continuum and line emission maps at 230 GHz and 345 GHz obtained from a single night's observation of the Galactic Center with the SMA and - for the first time - with the Atacama Large Millimeter Array (ALMA) at 230 GHz. While the ALMA mosaic covers only the mini-spiral region, the SMA data includes also most parts of Sagittarius A West and the surrounding circumnuclear disk. Sgr A West is partially detected in continuum emission and the H30alpha (~231 GHz) recombination line emission map outlines well the distribution of the ionized gas as well as its radial motion. I present the first high resolution (5") map of the Galactic Center region in CO(3-2) emission - it traces the molecular gas in the circumnuclear disk. For future analyses of the variability of Sgr A*, I extracted the lightcurves of the Sgr A*. They show a significant difference in the average flux level between the two observations with ALMA and SMA, that are separated by only 2.5 hours.