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| Paper: |
A New Approach to Detailed Structural Decomposition: Kicked-up Disk Stars in Andromeda's Halo? |
| Volume: |
480, Structure and Dynamics of Disk Galaxies |
| Page: |
47 |
| Authors: |
Dorman, C. E.; Widrow, L. M.; Guhathakurta, P.; PHAT collaboration |
| Abstract: |
We characterize the bulge, disk, and halo subcomponents in the
Andromeda galaxy (M31) over the radial range 0.4 kpc < Rproj < 225 kpc. The cospatial nature of these subcomponents renders
them difficult to disentangle using surface brightness (SB)
information alone, especially interior to ∼ 20 kpc.
Our new decomposition technique combines information
from the luminosity function (LF) of over 1.5 million bright (20 < mF814W < 22) stars from the Panchromatic Hubble Andromeda
Treasury (PHAT) survey, radial velocities of
over 5000 red giant branch stars in the same magnitude range from the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH) survey, and integrated I-band SB profiles from
various sources. We use an affine-invariant Markov chain Monte Carlo algorithm to fit an
appropriate toy model to these three data sets. The bulge, disk, and halo
SB profiles are modeled as a Sérsic, exponential, and cored power-law,
respectively, and the LFs are modeled as broken
power-laws. We find that the number of stars with a disk-like LF is
∼ 5% larger than the number in the dynamically cold component,
suggesting that some stars born in the disk have been dynamically
heated to the point that they are kinematically indistinguishable from
halo members. This is the first kinematical evidence for a “kicked-up
disk” population in the stellar halo of M31. The fraction of kicked-up disk stars is
consistent with that found in simulations. See Dorman et al. (2013) for more
information. |
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