The Formation History of UGC 12591 - the Most Massive Known Field S0 Galaxy
Abstract
We propose to determine the formation history of UGC12591 - the most massive known field S0 galaxy in the nearby Universe {D 98Mpc}. Its maximum rotational velocity of 483 km/s yields a dynamical mass within 50 kpc of 2x10^12 solar masses. Given its field location, this poses the question of how such a massive bulge can grow in isolation? To trace the UGC12591 star formation and assembly history we will use the properties of its globular clusters {GCs} and massive compact stellar systems which are expected in huge numbers given its mass. In particular, GCs are well known to be among the best indicators of major {merger} galaxy formation episodes, capturing the physical conditions at the time of their formation. With the wide spectral coverage of the proposed obesrvations, we will 1} search for multiple/intermediate-age GC populations and 2} measure whether the specific frequency of the metal-rich GCs relative to the bulge luminosity is enhanced. If any of these points are confirmed, this would strongly favor a merger-driven {gas-rich} as opposed to "passive" bulge growth {secular evolution}. The only possible way to derive robust photometric GC ages and metallicities at the distance of UGC12591 in a reasonable amount of time is by employing the efficiency of HST/WFC3 and the age-metallicity sensitive V, I, H filter combination {F606W, F814W, F160W}. In four orbits we will observe the brighter half of the GC population of UGC12591, which will enable us to derive GC population peak age and metallicity {+/- 20%}.The results from this proposal will offer an important leap forward in our understanding of the assembly history of extremely massive isolated S0 galaxies.
- Publication:
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HST Proposal
- Pub Date:
- October 2013
- Bibcode:
- 2013hst..prop13370G