A Deeper Look at Leo IV: Star Formation History and Extended Structure - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado




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Abstract: We present MMT-Megacam imaging of the Leo~IV dwarf galaxy in order toinvestigate its structure and star formation history, and to search for signsof association with the recently discovered Leo~V satellite. Based onparameterized fits, we find that Leo~IV is round, with $\epsilon < 0.23$ atthe 68\% confidence limit and a half-light radius of $r {h} \simeq 130$ pc.Additionally, we perform a thorough search for extended structures in the planeof the sky and along the line of sight. We derive our surface brightnessdetection limit by implanting fake structures into our catalog with stellarpopulations identical to that of Leo~IV. We show that we are sensitive tostream-like structures with surface brightness $\mu {r}\lesssim29.6$ magarcsec$^{-2}$, and at this limit, we find no stellar bridge between Leo IV outto a radius of $\sim$0.5 kpc and the recently discovered, nearby satellite LeoV. Using the color magnitude fitting package StarFISH, we determine that Leo~IVis consistent with a single age $\sim$14 Gyr, single metallicity$Fe-H\sim-2.3$ stellar population, although we can not rule out asignificant spread in these value. We derive a luminosity of$M {V}=-5.5\pm0.3$. Studying both the spatial distribution and frequency ofLeo~IV-s -blue plume- stars reveals evidence for a young $\sim$2 Gyr stellarpopulation which makes up $\sim$2\% of its stellar mass. This sprinkling ofstar formation, only detectable in this deep study, highlights the need forfurther imaging of the new Milky Way satellites along with theoretical work onthe expected, detailed properties of these possible -reionization fossils-.



Autor: D.J. Sand, A. Seth, E.W. Olszewski, B. Willman, D. Zaritsky, N. Kallivayalil

Fuente: https://arxiv.org/







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