National Astronomical Observatory of Japan | ALMA | 2015 June 18
[c][imghover=http://asterisk.apod.com/download/file.php?id=18337]http://asterisk.apod.com/download/file.php?id=18336[/imghover][hr][/hr]1. Central region of NGC 1097 observed with ALMA. The distribution of hydrogen cyanideA research group led by Kyoko Onishi at the SOKENDAI (The Graduate University for Advanced Studies) observed the barred spiral galaxy NGC 1097 with ALMA and found that the central supermassive black hole (SMBH) has a mass 140 million times the mass of the Sun. Since galaxies are believed to have co-evolved with SMBHs, SMBH mass is an important parameter in understanding their relation in the context of galaxy evolution. This research result is based on the ALMA observation data obtained within a two-hour observation, which demonstrates the outstanding capacity of ALMA in the SMBH mass measurement.
(HCN) is indicated in red and formyl cation (HCO+) in green, and synthesized with an
optical image taken by the Hubble Space Telescope.
2. Velocity of the HCN gas is shown in the color. Red indicates gas is moving away
from us while blue is coming closer to us.
Credit: ALMA (ESO/NAOJ/NRAO), K. Onishi (SOKENDAI), NASA/ESA Hubble[/i][/c][hr][/hr]
It is thought that a majority of the galaxies in the universe have a massive black hole in the galactic center. Since these black holes have masses of several millions to tens of billions of solar masses, they are called "supermassive black holes (SMBHs)". Recent observation results suggest the correlation between the SMBH mass and the central bulge mass/luminosity of the host galaxy. Such correlation indicates that SMBHs may have a key role in the growth and evolution of galaxies.
SMBH mass is an essential parameter to reveal the correlation between the SMBH and the host galaxy. There are several methods to derive the SMBH mass, one of which is using proper motion of stars and megamasers (astrophysical objects that emit strong radio waves) around the SMBH to estimate the gravity of the SMBH applied to the observed objects. This measurement method, however, is difficult and not suitable for the most galaxies because it requires observations of the regions around the SMBH with very high angular resolution (*1 and *2) . Another method is using ionized gas dynamics distributed in the host galaxy bulge. Ionized gas, however, is easily affected by non-circular motion such as inflow or outflow of gas, in addition to the gravity of the SMBH. This makes it difficult to accurately measure SMBH mass for a large number of galaxies. The method most commonly used to estimate SMBH mass is the one using stellar dynamics in host galaxies, although its application is rather limited to elliptical galaxies and thus it won't be a versatile SMBH mass measurement method applicable to wide ranging types of galaxies.
An alternative to these conventional methods is to derive the SMBH mass from molecular gas dynamics in the central region of a galaxy, which was formulated by Davis et al. at the European Southern Observatory (ESO). This method has the advantage that molecular gas is less susceptible to environmental conditions compared to stars and ionized gas, and therefore the motion affected by SMBH gravity can be measured more easily. Davis et al. made observations of a galaxy NGC 4526 for tens of hours with a radio telescope called CARMA and estimated the mass of the central SMBH. ...
ALMA Weighs Supermassive Black Hole at Center of Distant Spiral Galaxy
National Radio Astronomy Observatory | ALMA | 2015 Jun 18
A Measurement of the Black Hole Mass in NGC 1097 Using ALMA - K. Onishi et al
- Astrophysical Journal 806(1) 39 (2015 Jun 10) DOI: 10.1088/0004-637X/806/1/39
