Does the Ursa Minor Dwarf Spheroidal Host an Intermediate-Mass Black Hole?


There is a milli-Jansky radio source in the core of the nearby dwarf spheroidal galaxy in Ursa Minor, UGC 9749, which may well be an intermediate-mass black hole. The radio source is within 20 ## of the center of UGC 9749 --- the likelihood of an unrelated background source being this close to the center is only <1%. Our 1.7 GHz VLBI observations showed that the radio source has a core of size <2 mas. If the radio source is in fact associated with UGC 9749, and thus at a distance of only 66 kpc, it is quite unusual, and likely to be an intermediate-mass black hole, of which only a very few examples are known or suspected. The most convincing way to rule out the possibility of an unrelated background quasar is to determine if its proper motion is equal to that of UGC 9749, which is 0.55 0.17 mas year -1 . Phase-referenced VLBI astrometry on the compact core should allow us to determine a su#ciently accurate proper motion within 2 years. We propose two epochs of VLBI observations, spaced >1.5 years apart, to measure this proper motion and determine whether the Ursa Minor dwarf spheroidal has an active galactic nucleus with an intermediate-mass black hole in its center.

Name Other * Institution Email Phone
Michael Bietenholz PI York University 416 736-2100 ext 60259
Norbert Bartel York University 416 736-5424
* PI = Principal Investigator; CO = Contact author; T = Thesis observations; S = Student

Front Ends
Gregorian C(3.95 to 5.85 GHz)

Back Ends
VLBA recorder and DAR

Type of Observing
Monitor Very Long Baseline Interferometry

Switching Type

Processor (correlator)

Allotted time 16.00 hours

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Updated 09/19/2007