1Dept. of Astronomy, The Ohio State University, 140
W. 18th Ave., Columbus, OH 43210; khan, kstanek, ckochanek@astronomy.ohio-state.edu
2Center for Cosmology and AstroParticle Physics,
The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210
Finding
Car
Khan et al. 2011
Abstract:
The late-stage evolution of the most massive stars such as
![$\eta $](img1.png)
Carinae is controlled
by the effects of mass loss, which may be dominated by poorly understood eruptive
mass ejections. Understanding this population is challenging because no true
analogs of
![$\eta $](img1.png)
Car have been clearly identified in the Milky Way or other galaxies. We utilize
Spitzer IRAC images of 7 nearby (
![$\lesssim4$](img33.png)
Mpc) galaxies to search for such analogs.
We find 34 candidates with a flat or rising mid-IR spectral energy
distributions towards longer mid-infrared wavelengths that emit
![$>10^5$](img34.png)
L
![$_\odot $](img7.png)
in the IRAC bands (3.6 to 8.0
![$\micron$](img35.png)
) and are
not known to be background sources. Based on our estimates for the expected
number of background sources, we expect that follow-up observations will show that most of
these candidates are not dust enshrouded massive stars, with an expectation of only
![$6\pm6$](img36.png)
surviving candidates. Since we would detect true analogs of
![$\eta $](img1.png)
Car for roughly
200 years post-eruption, this implies that the rate of eruptions like
![$\eta $](img1.png)
Car is
less than the ccSN rate. It is possible, however, that every M
![$>40$](img37.png)
M
![$_\odot $](img7.png)
star undergoes such eruptions given our initial results. In PaperII we will characterize the candidates through further analysis
and follow-up observations, and there is no barrier to increasing the galaxy sample
by an order of magnitude.
stars: evolution, mass-loss, winds, outflows
-- stars: individual: Eta Carinae
-- galaxies: individual (M33, M81, NGC247, NGC300, NGC2403, NGC6822, NGC7793)
Finding
Car Analogs in Nearby Galaxies Using Spitzer:
I. Candidate Selection
Rubab Khan1,
K. Z. Stanek1,2,
C. S. Kochanek1,2
Rubab Khan
2012-10-28