First stellar spectroscopy in Leo P. (arXiv:1901.01295v1 [astro-ph.SR])

First stellar spectroscopy in Leo P. (arXiv:1901.01295v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Evans_C/0/1/0/all/0/1">C. J. Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Castro_N/0/1/0/all/0/1">N. Castro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzalez_O/0/1/0/all/0/1">O. A. Gonzalez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garcia_M/0/1/0/all/0/1">M. Garcia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bastian_N/0/1/0/all/0/1">N. Bastian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cioni_M/0/1/0/all/0/1">M.-R. L. Cioni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clark_J/0/1/0/all/0/1">J. S. Clark</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davies_B/0/1/0/all/0/1">B. Davies</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferguson_A/0/1/0/all/0/1">A. M. N. Ferguson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamann_S/0/1/0/all/0/1">S. Kamann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lennon_D/0/1/0/all/0/1">D. J. Lennon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Patrick_L/0/1/0/all/0/1">L. R. Patrick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vink_J/0/1/0/all/0/1">J. S. Vink</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weisz_D/0/1/0/all/0/1">D. R. Weisz</a>

We present the first stellar spectroscopy in the low-luminosity (M_V ~-9.3
mag), dwarf galaxy Leo P. Its significantly low oxygen abundance (3% solar) and
relative proximity (~1.6 Mpc) make it a unique galaxy to investigate the
properties of massive stars with near-primordial compositions akin to those in
the early Universe. From our VLT-MUSE spectroscopy we find the first direct
evidence for an O-type star in the prominent HII region. The spectroscopic
confirmation of such a massive star supports arguments that the upper limit to
the initial mass function, even if sparsely sampled, is not signficantly
influenced by the low star-formation rate of Leo P. We classify 14 further
sources as massive stars (and 17 more as candidate massive stars), most likely
B-type objects. From comparisons with published evolutionary models we argue
that the absolute visual magnitudes of massive stars in very metal-poor systems
such as Leo P and I Zw 18 may be fainter by ~0.5 mag compared to Galactic
stars. We also present spectroscopy of two carbon stars identified previously
as candidate asymptotic-giant-branch stars. Two of three further candidate
asymptotic-giant-branch stars display CaII absorption, confirming them as cool,
evolved stars; we also recover CaII absorption in the stacked data of the next
brightest 16 stars in the upper red giant branch. These discoveries will
provide targets for future observations to investigate the physical properties
of these objects and to calibrate evolutionary models of luminous stars at such
low metallicity. The MUSE data also reveal two 100pc-scale ring structures in
Halpha emission, with the HII region located on the northern edge of the
southern ring. Lastly, we report serendipitous observations of 20 galaxies,
with redshifts ranging from z=0.39, to a close pair of star-forming galaxies at
z=2.5.

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