Ultra-Faint Milky Way Satellites Discovered in Carina, Phoenix, and Telescopium with DELVE Data Release 3
Authors
C. Y. Tan
W. Cerny
A. B. Pace
J. A. Sharp
K. Overdeck
A. Drlica-Wagner
J. D. Simon
B. Mutlu-Pakdil
D. J. Sand
A. M. Senkevich
D. Erkal
P. S. Ferguson
F. Sobreira
K. R. Atzberger
J. L. Carlin
A. Chiti
D. Crnojević
A. P. Ji
L. C. Johnson
T. S. Li
G. Limberg
C. E. Martínez-Vázquez
G. E. Medina
V. M. Placco
A. H. Riley
E. J. Tollerud
A. K. Vivas
T. M. C. Abbott
M. Aguena
O. Alves
D. Bacon
S. Bocquet
D. Brooks
D. L. Burke
R. Camilleri
J. A. Carballo-Bello
A. Carnero Rosell
J. Carretero
T. -Y. Cheng
Y. Choi
L. N. da Costa
M. E. da Silva Pereira
T. M. Davis
J. De Vicente
S. Desai
P. Doel
S. Everett
B. Flaugher
J. Frieman
J. García-Bellido
D. Gruen
G. Gutierrez
S. R. Hinton
D. L. Hollowood
D. J. James
K. Kuehn
S. Lee
J. L. Marshall
J. Mena-Fernández
F. Menanteau
R. Miquel
J. Myles
M. Navabi
D. L. Nidever
R. L. C. Ogando
A. A. Plazas Malagón
A. Porredon
S. Samuroff
E. Sanchez
D. Sanchez Cid
I. Sevilla-Noarbe
M. Smith
E. Suchyta
M. E. C. Swanson
V. Vikram
A. R. Walker
A. Zenteno
Abstract
We report the discovery of three Milky Way satellite candidates: Carina IV, Phoenix III, and DELVE 7, in the third data release of the DECam Local Volume Exploration survey (DELVE). The candidate systems were identified by cross-matching results from two independent search algorithms. All three are extremely faint systems composed of old, metal-poor stellar populations ($τ\gtrsim 10$ Gyr, [Fe/H] $ \lesssim -1.4$). Carina IV ($M_V = -2.8;\ r_{1/2} = 40 {\rm pc}$) and Phoenix III ($M_V = -1.2;\ r_{1/2} = 19 {\rm pc}$) have half-light radii that are consistent with the known population of dwarf galaxies, while DELVE 7 ($M_V = 1.2;\ r_{1/2} = 2 {\rm pc}$) is very compact and seems more likely to be a star cluster, though its nature remains ambiguous without spectroscopic followup. The Gaia proper motions of stars in Carina IV ($M_* = 2250^{+1180}_{-830} {\rm M_\odot}$) indicate that it is unlikely to be associated with the LMC, while DECam CaHK photometry confirms that its member stars are metal-poor. Phoenix III ($M_* = 520^{+660}_{-290} {\rm M_\odot}$) is the faintest known satellite in the extreme outer stellar halo ($D_{\rm GC} > 100$ kpc), while DELVE 7 ($M_* = 60^{+120}_{-40} {\rm M_\odot}$) is the faintest known satellite with $D_{\rm GC} > 20$ kpc.
