CaltechAUTHORS
  A Caltech Library Service

Planetary camera observations of the central parsec of M32

Lauer, Tod R. and Faber, S. M. and Currie, Douglas G. and Ewald, S. P. and Groth, Edward J. and Hester, J. Jeff and Holtzman, Jon A. and Light, Robert M. and O'Neill, Earl J., Jr. and Shaya, Edward J. and Westphal, James A. (1992) Planetary camera observations of the central parsec of M32. Astronomical Journal, 104 (2). pp. 552-562. ISSN 0004-6256. doi:10.1086/116254. https://resolver.caltech.edu/CaltechAUTHORS:20141204-065501740

[img]
Preview
PDF - Published Version
See Usage Policy.

2MB

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20141204-065501740

Abstract

Analysis of V band HST Planetary Camera images of the elliptical galaxy M32 shows that its nucleus is extremely dense and remains unresolved at even the HST diffraction limit. A combined approach of image deconvolution and model fitting is used to investigate the starlight distribution into limiting radii of 0".04 (0.14 pc at 700 kpc). The logarithmic slope of the brightness profile smoothly flattens from y= -1.2 at 3.4 pc to y= -0.5 at 0.34 pc; interior to this radius the profile is equally consistent with a singular µ(r)∝ r,^(-1/2) cusp or a small nonisothermal core with r_c<0.37 pc. The isophotes maintain constant ellipticity into tlle center, and there is no evidence for a central point source, disk, dust, or any other substructures. The cusp model implies central mass densities p_0 > 3 X 10^7 M_☉ pc^(-3) at the resolution limit and is consistent with a central M_• = 3 X 10^6 M_☉ black hole; the core model implies p_0≈4 X 10^6 M_☉ pc^(-3). From the viewpoint of long-term stability, we argue that a starlight cusp surrounding a central black hole is the more plausible interpretation of the observations. A core at the implied density and size without a black hole has a relaxation time of only ~7 X 10^7 yr and a short stellar oollision timescale implying wholesale stellar merging over the age of the universe. The core would be strongly vulnerable to collapse and concomitant runaway stellar merging. Collapse may lead to formation of a massive black hole in any case if it cannot be reversed by formation of a binary from high-mass merger products. Regardless of the ultimate fate of the core, however, structural evolution of the core will always be accompanied by strong evolution of the core population-the constant isophote shape and absence of a central color gradient appear to show that such evolution has not occurred. In contrast, the high velocities around a black hole imply long relaxation and stellar collision times for the cusp population compared to the age of the universe.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://adsabs.harvard.edu//abs/1992AJ....104..552LarXivArticle
http://dx.doi.org/10.1086/116254DOIArticle
ORCID:
AuthorORCID
Faber, S. M.0000-0003-4996-214X
Ewald, S. P.0000-0002-1567-9154
Additional Information:© 1992 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 5 March 1992; revised 21 April 1992. We thank Dr. Jeremy Goodman for useful conversations. This research was conducted by the WFPC Investigation Definition Team, supported in part by NASA Grant No. NAS5-1661.
Funders:
Funding AgencyGrant Number
NASANAS5-1661
Issue or Number:2
DOI:10.1086/116254
Record Number:CaltechAUTHORS:20141204-065501740
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141204-065501740
Official Citation:Planetary camera observations of the central parsec of M32 Lauer, Tod R.; Faber, S. M.; Currie, Douglas G.; Ewald, S. P.; Groth, Edward J.; Hester, J. Jeff; Holtzman, Jon A.; Light, Robert M.; O'Neil, Earl J., Jr.; Shaya, Edward J.; Westphal, James A. Astronomical Journal (ISSN 0004-6256), vol. 104, no. 2, Aug. 1992, p. 552-562.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52363
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:04 Dec 2014 21:01
Last Modified:10 Nov 2021 19:25

Repository Staff Only: item control page