A Massive Black Hole in a
Possible Relic Galaxy
New results based on Gemini observations
of the compact, early-type galaxy NGC 1277
yield a new, lower than previously determined, mass of its central supermassive black
hole. The work also has more profound implications for galaxy formation, suggesting that
massive black holes were formed before stars
came into place.
Jonelle Walsh (Texas A&M University) and
collaborators used the Near-infrared Integral
Field Spectrometer (NIFS) and laser-assisted
adaptive optics on the Gemini North telescope
to obtain high-resolution observations within
about 1,400 light years of NGC 1277’s center.
These provide both sensitive data within the
black hole sphere of influence and simultaneously cover extended regions where stars are
more important. The team used these data
to determine a lower black hole mass — by a
factor of about three (4.9 x 109 MSun) — compared with earlier findings; still the black hole
at the heart of this galaxy remains one of the
most massive ever measured.
This result puts NGC 1277 well above the
standard relationship between black hole
mass and galaxy luminosity, placing it close
to the relationship between black hole mass
and bulge stellar velocity dispersion (the “Msigma relation”; Figure 3). These observations
and previous work identify NGC 1277 as a relic
galaxy — one that has suffered only passive
evolution (the aging of stars) over time, rather
than the mergers and transformations that
result in giant elliptical galaxies in the nearby
Universe. Such relics offer windows into the
early Universe and galaxy formation.
Based on these results and similar examples,
the authors suggest that black holes formed
first, followed by star formation, to end up
with galaxies that exhibit the usual relations. The complete paper will be published
in The Astrophysical Journal, and a preprint
is now available.
Nancy A. Levenson is Deputy Director and Head
of Science at Gemini Observatory and can be
reached at: [email protected]
Figure 3.
NGC 1277 and other
similar rotating, highdispersion, early-type
galaxies (red) are
consistent with the
M-sigma relation
(left), but appear to be
overluminous relative
to their black hole
mass (right).
January 2016
GeminiFocus
9