AsianScientist (Jun. 24, 2015) – A research group at the SOKENDAI (The Graduate University for Advanced Studies) observed the barred spiral galaxy NGC 1097 with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope and found that the central supermassive black hole (SMBH) has a mass 140 million times the mass of the Sun. Their findings have been published in The Astrophysical Journal.
A research team led by Ms. Kyoko Onishi, a doctoral student at the SOKENDAI doing her research at the National Astronomical Observatory of Japan (NAOJ), took on a challenge to derive the mass of the SMBH in the central region of the galaxy NGC 1097 using ALMA observation data. ALMA’s high sensitivity enabled the team to measure gas velocity with high accuracy.
“Recent observation results indicate the relationship between SMBH mass and host galaxy properties varies depending on the type of galaxies, which makes it more important to derive accurate SMBH masses in various types of galaxies,” Onishi said.
The research team made precise measurement of the distribution and kinematics of molecular gas by observing emission lines from hydrogen cyanide (HCN) and formyl cation (HCO+) with ALMA, and then examined the gravitational motion of the molecular gas by making some astrophysical models.
Since the gravity applied to the molecular gas differs depending on the SMBH mass as well as the density and distribution of stars in the bulge, the gas motion was calculated by making models assuming various cases in order to find a model which is best fitted for the observation data.
As a result of the calculation, it was found that the central SMBH of NGC1097 has a mass 140 million times the solar mass. This is the first SMBH mass measurement to be made using this method in late-type galaxies (e.g. spiral and barred spiral galaxies).
“We could obtain the kinematics data of the central molecular gas in NGC 1097 within a two-hour ALMA observation. To reveal the relation between the SMBH and the host galaxy, we need to derive more SMBH masses in various types of galaxies. ALMA will enable us to observe a large number of galaxies in a practical length of time,” said Onishi, expressing her expectations for future ALMA observations.
Measuring the mass of SMBHs is the first step to solving the long-standing mysteries about how galaxies and SMBHs have been formed and co-evolved.
The article can be found at: Onishi et al. (2015) A Measurement Of The Black-Hole Mass In NGC 1097 Using ALMA.
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Source: ALMA, National Astronomical Observatory of Japan.
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