Bibcode
Comerón, Sébastien; Elmegreen, Bruce G.; Knapen, J. H.; Salo, Heikki; Laurikainen, Eija; Laine, Jarkko; Athanassoula, E.; Bosma, Albert; Sheth, Kartik; Regan, Michael W.; Hinz, Joannah L.; Gil de Paz, Armando; Menéndez-Delmestre, Karín; Mizusawa, Trisha; Muñoz-Mateos, Juan-Carlos; Seibert, Mark; Kim, Taehyun; Elmegreen, Debra M.; Gadotti, Dimitri A.; Ho, Luis C.; Holwerda, Benne W.; Lappalainen, Jani; Schinnerer, Eva; Skibba, Ramin
Bibliographical reference
The Astrophysical Journal, Volume 741, Issue 1, article id. 28 (2011).
Advertised on:
11
2011
Journal
Citations
106
Refereed citations
95
Description
Most, if not all, disk galaxies have a thin (classical) disk and a thick
disk. In most models thick disks are thought to be a necessary
consequence of the disk formation and/or evolution of the galaxy. We
present the results of a study of the thick disk properties in a sample
of carefully selected edge-on galaxies with types ranging from T = 3 to
T = 8. We fitted one-dimensional luminosity profiles with physically
motivated functions—the solutions of two stellar and one gaseous
isothermal coupled disks in equilibrium—which are likely to yield
more accurate results than other functions used in previous studies. The
images used for the fits come from the Spitzer Survey of Stellar
Structure in Galaxies (S4G). We found that thick disks are on
average more massive than previously reported, mostly due to the
selected fitting function. Typically, the thin and thick disks have
similar masses. We also found that thick disks do not flare
significantly within the observed range in galactocentric radii and that
the ratio of thick-to-thin disk scale heights is higher for galaxies of
earlier types. Our results tend to favor an in situ origin for most of
the stars in the thick disk. In addition, the thick disk may contain a
significant amount of stars coming from satellites accreted after the
initial buildup of the galaxy and an extra fraction of stars coming from
the secular heating of the thin disk by its own overdensities. Assigning
thick disk light to the thin disk component may lead to an underestimate
of the overall stellar mass in galaxies because of different
mass-to-light ratios in the two disk components. On the basis of our new
results, we estimate that disk stellar masses are between 10% and 50%
higher than previously thought and we suggest that thick disks are a
reservoir of "local missing baryons."
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