Related papers: Pericenter passage of the gas cloud G2 in the Gala…
In recent years, the evidence for the existence of an ultra-compact concentration of dark mass associated with the radio source Sgr A* in the Galactic Center has become very strong. However, an unambiguous proof that this object is indeed a…
C/2017 K2 (PANSTARRS) is an Oort cloud comet previously observed to be active at heliocentric distances r>20 au on what is likely its first passage through the inner solar system. We observed the comet on 2021 March 19-20 at r=6.82 au…
An unusual object, G2, had its pericenter passage around Sgr A*, the $4\times10^6$ M$_\odot$ supermassive black hole in the Galactic Centre, in Summer 2014. Several research teams have reported evidence that following G2's pericenter…
We report a new 1-pc (30") resolution CS($J=2-1$) line map of the central 30 pc of the Galactic Center (GC), made with the Nobeyama 45m telescope. We revisit our previous study of the extraplanar feature called polar arc (PA), which is a…
We present a near-infrared study of the Seyfert 2 galaxy NGC\,6300, based on subarcsecond images and long slit spectroscopy obtained with Flamingos-2 at Gemini South. We have found that the peak of the nuclear continuum emission in the…
The black hole at the center of our Milky Way Galaxy -- the Galactic Black Hole, or GBH -- is a rather modest representative of its class. With a mass of 4 x 10^6 solar masses, it is well over a thousand times less massive than the most…
We report new astrometric and spectroscopic observations of the star S2 orbiting the massive black hole in the Galactic Center, which were taken at the ESO VLT with the adaptive optics assisted, near-IR camera NAOS/CONICA and the near-IR…
A possibility of time-delayed radio brightenings of Sgr A* triggered by the pericenter passage of the G2 cloud is studied by carrying out global three-dimensional magnetohydrodynamic simulations taking into account the radiative cooling of…
The young stars near the supermassive black hole at the galactic center follow orbits that are nearly random in orientation and that have an approximately thermal distribution of eccentricities, N(e) ~ e. We show that both of these…
Winds from massive stars supply ~ 10^{-3} solar masss/year of gas to the central parsec of the Galactic Center. Spherically symmetric hydrodynamic calculations show that ~ 1 % of this gas, or ~ 10^{-5} solar masses/year, flows in towards…
Despite strong physical reasons that they should exist and decades of search, jets from the Galactic Center Black Hole, Sgr A*, have not yet been convincingly detected. Based on high-resolution Very Large Array images and ultra-deep…
Lada et al. recently presented a detailed near-infrared extinction map of Globule G2 in the Coalsack molecular cloud complex, showing that this starless core has a well-defined central extinction minimum. We propose a model for G2 in which…
Sagittarius A* (Sgr A*) is the central supermassive black hole with the mass $\sim 4\times 10^6 M_{\odot}$ in the Milky Way and stars are orbiting around it. In May 2018, one of the nearest stars to Sgr A* named S0-2/S2 experienced the…
Edge Cloud 2 (EC2) is a molecular cloud, about 35 pc in size, with one of the largest galactocentric distances known to exist in the Milky Way. We present observations of a peak CO emission region in the cloud and use these to determine its…
(Abridged) The two-dimensional distribution and kinematics of the molecular, ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies have been measured using high spatial resolution (~0''.09) near-infrared spectroscopy…
Aims. We have investigated neutral gas in the central cavity of the circumnuclear disk (CND) at the Galactic Center, where the ionized minispiral lies, to describe the H2 distribution and properties in this ionized environment. Methods.…
The S-star cluster in the Galactic center allows us to study the physics close to a supermassive black hole, including distinctive dynamical tests of general relativity. Our best estimates for the mass of and the distance to Sgr A* using…
We present the first detection from the Spitzer Space Telescope of 4.5 micron variability from Sgr A*, the emitting source associated with the Milky Way's central black hole. The >23 hour continuous light curve was obtained with the IRAC…
The Sagittarius B2 (Sgr B2) molecular cloud complex is an X-ray reflection nebula whose total emissions have continued to decrease since 2001 as it reprocesses one or more past energetic outbursts from the supermassive black hole…
This thesis includes two main projects. In the first part, we assess the feasibility of a recently suggested strong-field general relativity test, in which future observations of a hypothetical class of stars orbiting very close to the…