Precise 'weight check' of black hole
A research group led by Kyoko Onishi at the SOKENDAI (The Graduate University for Advanced Studies), including a researcher in the National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 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.
This is the central region of NGC 1097 observed with ALMA. The velocity of the HCN gas is shown in the color and overlaid on the optical image taken by the Hubble Space Telescope. Red indicates gas is moving away from us while purple is coming closer to us.
Credit: ALMA (ESO/NAOJ/NRAO), K. Onishi (SOKENDAI), NASA/ESA Hubble Space Telescope
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.
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.
Observations with ALMA:
A research team led by Kyoko Onishi, a doctoral student at the SOKENDAI (The Graduate University for Advanced Studies) 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 (*3) using ALMA observation data. ALMA's high sensitivity enables the team to measure gas velocity with high accuracy.
"While NGC 4526, observed by a team led by Davis, is a lenticular galaxy, NGC 1097 is a barred spiral galaxy. 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 using this method in late-type galaxies (e.g. spiral and barred spiral galaxies).
Onishi said, expressing her expectations for future ALMA observations, "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."
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. This research assures ALMA's capability in this field.
*1) The method to derive the SMBH mass using the proper motion of stars around the SMBH is applicable only to the black hole at the center of our Milky Way galaxy. This method cannot be extended to other galaxies, which are too far to observe individual stars in the central region separately.
*2) In 1993, a high-velocity maser was observed in the central region of the galaxy NGC4258 with the 45-m radio telescope at the NAOJ Nobeyama Radio Observatory. This was the first observational evidence for the presence of a SMBH. However this method cannot be used to derive SMBH masses in a majority of galaxies because only a very scarce number of masers have been found around SMBHs.
*3) NGC 1097 is a barred spiral galaxy about 47 million light years away in the direction of the constellation of Fornax.
Paper / Research Team:
This observation result was published Onishi et al. "A Measurement of the Black-Hole Mass in NGC 1097 using ALMA" in the Astrophysical Journal, issued in June 2015.
This research was conducted by:
This research is supported by JSPS Grants-in-Aid for Scientific Research (No. 26*368).
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
Graduate student, SOKENDAI (The Graduate University for Advanced Studies), Japan
Chief Public Information Officer, National Astronomical Observatory of Japan
Masaaki Hiramatsu | EurekAlert!
When fluid flows almost as fast as light -- with quantum rotation
22.06.2018 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
Thermal Radiation from Tiny Particles
22.06.2018 | Universität Greifswald
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
22.06.2018 | Materials Sciences
22.06.2018 | Earth Sciences
22.06.2018 | Life Sciences