Accretion and Star Formation Induced by the Galactic Center Supermassive Black Hole Sgr A*

Project: Research project

Project Details


Overview: In the proposed observational and theoretical program, we aim to investigate the processes that lead to accretion onto Sgr A* and establish ongoing star formation in the tidal field of Sgr A*. The processes that lead to accretion are closely related to star formation in the nuclei of galaxies that host massive black holes. We will study a disk-based mode of star formation, entirely distinct from the standard cloud-based mode observed in the Galactic disk, as well as the underluminous nature of Sgr A*. We will monitor the variability of the black hole as a cloud of gas, G2, encounters the atmosphere of Sgr A* in the next few years. In addition, we have a multi-pronged observational approach to identify sites of ongoing star formation near Sgr A*.
Intellectual Merit: The nucleus of our Galaxy centered on the 4×106 M� black hole Sgr A* is an excellent site to examine the nature of star formation and accretion onto a massive black hole. These studies have far reaching implications on the nature of star formation and AGN activity in the nuclei of more active galaxies hosting massive black holes. Our understanding of star formation near a supermassive black hole will shed light on the nature of accretion flow onto the massive black hole. For example, does star formation near a black hole suppress mass accretion or does it enhance accretion onto the massive black hole? Here, we examine these two related topics. We have a number of observations that are either scheduled or being planned to determine if ongoing
star formation is taking place in the last few 104−105 years. We are also scheduled in 2013 and 2014 to observe the G2 cloud as it approaches the black hole. These observations include searching for protostellar outflows, SED fitting of young stellar objects, water and methanol masers and compact HII regions within the inner 2pc of the Galaxy. The evidence for on-going star formation will establish that the cluster of massive stars orbiting Sgr A* has not migrated toward the Galactic center but actually formed near the massive black hole. We will also study possible mechanisms that could increase the gas density above the threshold to overcome the critical Roche density, so that star formation can take place near the black hole. Recent analytical and numerical simulations assume that equal fractions of star forming material are accreted onto Sgr A*, providing the needed energetics to produce the Fermi γ-ray bubbles. We plan to explore the idea that the Fermi γ-ray bubbles were produced in terms of simultaneous star formation and accretion near the central black holes in the context of the cloud capture model.
Broader impact: The PI and D. Roberts have extensive experience in communicating science and research to the public and are committed to continuing these efforts in this project. The team will make all FITS images related to this project available to the professional and citizen science communities. These FITS images will be hosted at Northwestern University and will provide using a searchable database-driven website. We will make JPEG images for all FITS images and embed Astronomical Visual Metadata (AVM) tags into the JPEG headers for integration and display in AVM-capable visualization systems, such as WorldWide Telescope (WWT). AVM headers will have links to the publicly-available FITS files as well comprehensive captions for selected images. For the images of highest value, we will embed an HTML5/WebGL viewer using WWT on our website,
which will allow cross-fading between images at various wavelengths and resolu
Effective start/end date8/1/157/31/21


  • National Science Foundation (AST-1517246-001)


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