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Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey

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., Noel, 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. and Wechsler, R. H. (2020) Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey The Astrophysical Journal, 890 (2), 136.

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Abstract

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.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
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.
Noel, N.E.Dn.noel@surrey.ac.uk
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.
Date : 21 January 2020
Funders : University of Chicago Provost’s Scholar Award, NSF, CON-ICYT FONDECYT
DOI : 10.3847/1538-4357/ab6c67
Grant Title : NSF
Copyright Disclaimer : © 2020. The American Astronomical Society. All rights reserved.
Projects : NASA Fermi Guest Investigator Program Cycle 9, Fermilab LDRD
Additional Information : Embargo OK Metadata OK No Further Action
Depositing User : James Marshall
Date Deposited : 20 Aug 2020 15:07
Last Modified : 20 Aug 2020 15:07
URI: http://epubs.surrey.ac.uk/id/eprint/858456

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