Bibcode
Mau, S.; Cerny, W.; Pace, A. B.; Choi, Y.; Drlica-Wagner, A.; Santana-Silva, L.; Riley, A. H.; Erkal, D.; Stringfellow, G. S.; Adamów, M.; Carlin, J. L.; Gruendl, R. A.; Hernandez-Lang, D.; Kuropatkin, N.; Li, T. S.; Martínez-Vázquez, C. E.; Morganson, E.; Mutlu-Pakdil, B.; Neilsen, E. H.; Nidever, D. L.; Olsen, K. A. G.; Sand, D. J.; Tollerud, E. J.; Tucker, D. L.; Yanny, B.; Zenteno, A.; Allam, S.; Barkhouse, W. A.; Bechtol, K.; Bell, E. F.; Balaji, P.; Crnojević, D.; Esteves, J.; Ferguson, P. S.; Gallart, C.; Hughes, A. K.; James, D. J.; Jethwa, P.; Johnson, L. C.; Kuehn, K.; Majewski, S.; Mao, Y. -Y.; Massana, P.; McNanna, M.; Monachesi, A.; Nadler, E. O.; Noël, N. E. D.; Palmese, A.; Paz-Chinchon, F.; Pieres, A.; Sanchez, J.; Shipp, N.; Simon, J. D.; Soares-Santos, M.; Tavangar, K.; van der Marel, R. P.; Vivas, A. K.; Walker, A. R.; Wechsler, R. H.
Bibliographical reference
The Astrophysical Journal
Advertised on:
2
2020
Journal
Citations
58
Refereed citations
53
Description
We report the discovery of two ultra-faint stellar systems found in early data from the DECam Local Volume Exploration survey (DELVE). The first system, Centaurus I (DELVE J1238─4054), is identified as a resolved overdensity of old and metal-poor stars with a heliocentric distance of ${\text{}}{D}_{\odot }={116.3}_{-0.6}^{+0.6}\,\mathrm{kpc}$ , a half-light radius of ${r}_{h}={2.3}_{-0.3}^{+0.4}\,\mathrm{arcmin}$ , an age of $\tau \gt 12.85\,\mathrm{Gyr}$ , a metallicity of $Z={0.0002}_{-0.0002}^{+0.0001}$ , and an absolute magnitude of ${M}_{V}=-{5.55}_{-0.11}^{+0.11}\,\mathrm{mag}$ . This characterization is consistent with the population of ultra-faint satellites and confirmation of this system would make Centaurus I one of the brightest recently discovered ultra-faint dwarf galaxies. Centaurus I is detected in Gaia DR2 with a clear and distinct proper motion signal, confirming that it is a real association of stars distinct from the Milky Way foreground; this is further supported by the clustering of blue horizontal branch stars near the centroid of the system. The second system, DELVE 1 (DELVE J1630─0058), is identified as a resolved overdensity of stars with a heliocentric distance of ${\text{}}{D}_{\odot }={19.0}_{-0.6}^{+0.5}\,\mathrm{kpc}$ , a half-light radius of ${r}_{h}={0.97}_{-0.17}^{+0.24}\,\mathrm{arcmin}$ , an age of $\tau ={12.5}_{-0.7}^{+1.0}\,\mathrm{Gyr}$ , a metallicity of $Z={0.0005}_{-0.0001}^{+0.0002}$ , and an absolute magnitude of ${M}_{V}=-{0.2}_{-0.6}^{+0.8}\,\mathrm{mag}$ , consistent with the known population of faint halo star clusters. Given the low number of probable member stars at magnitudes accessible with Gaia DR2, a proper motion signal for DELVE 1 is only marginally detected. We compare the spatial position and proper motion of both Centaurus I and DELVE 1 with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC) and find that neither is likely to be associated with the LMC.
Related projects
Galaxy Evolution in the Local Group
Galaxy formation and evolution is a fundamental Astrophysical problem. Its study requires “travelling back in time”, for which there are two complementary approaches. One is to analyse galaxy properties as a function of red-shift. Our team focuses on the other approach, called “Galactic Archaeology”. It is based on the determination of galaxy
Matteo
Monelli