SAGITTARIUS II, DRACO II AND LAEVENS 3: THREE NEW MILKY WAY SATELLITES DISCOVERED IN THE PAN-STARRS 1 3π SURVEY

By Benjamin P. M. Laevens, N. Martin, E. Bernard, Edward F. Schlafly, B. Sesar, Hans-Walter Rix, Eric F. Bell, A. Ferguson, C. Slater, W. Sweeney and 12 more. 2015

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We present the discovery of three new Milky Way satellites from our search for compact stellar overdensities in the photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS 1, or PS1) 3π survey. The first satellite, Laevens 3, is located at a heliocentric distance of d = 67 ± 3 kpc. With a total magnitude of MV = −4.4 ± 0.3 and a half-light radius of rh = 7 ± 2 pc, its properties resemble those of outer halo globular clusters. The second system, Draco II/Laevens 4, is a closer and fainter satellite (d ∼ 20 kpc, MV = −2.9 ± 0.8), whose uncertain size ( r h = 19 − 6 + 8 pc ?> ) renders its classification difficult without kinematic information; it could either be a faint and extended globular cluster or a faint and compact dwarf galaxy. The third satellite, Sagittarius II/Laevens 5 (Sgr II), has an ambiguous nature, as it is either the most compact dwarf galaxy or the most extended globular cluster in its luminosity range ( r h = 37 − 8 + 9 pc ?> and MV = −5.2 ± 0.4). At a heliocentric distance of 67 ± 5 kpc, this satellite lies intriguingly close to the expected location of the trailing arm of the Sagittarius stellar stream behind the Sagittarius dwarf spheroidal galaxy (Sgr dSph). If confirmed through spectroscopic follow up, this connection would locate this part of the trailing arm of the Sagittarius stellar stream that has so far gone undetected. It would further suggest that Sgr II was brought into the Milky Way halo as a satellite of the Sgr dSph.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Farthest Neighbor: The Distant Milky Way Satellite Eridanus II (2016, background): “…data from the Dark Energy Survey (DES; Bechtol et al. 2015; Koposov et al. 2015; Drlica-Wagner et al. 2015a; Kim & Jerjen 2015) and other large optical surveys (Martin et al. 2015; Laevens et al. 2015a,b; Kim et al. 2015a,b; Torrealba et al. 2016a,b; Homma et al. 2016; Drlica-Wagner et al. 2016).”
A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters (2018, background): “The full sample consists of: Balbinot 1 (Balbinot et al. 2013); Laevens 1 and 2 (Laevens et al. 2014, 2015a); Kim 1 (Kim & Jerjen 2015a); Hor II (Kim & Jerjen 2015c); Hyd II (Martin et al. 2015); Gru I (Koposov et al. 2015a); Ind I (Kim et al. 2015b; Bechtol et al. 2015; Koposov et al. 2015a); and…”
ATLAS: A High-cadence All-sky Survey System (2018, background): “…square degrees) in 6 wavebands and is having a major impact—not only in transients and moving objects (Hsieh et al. 2012; Rest et al. 2014) but from low mass stars (Liu et al. 2013), through Milky Way stellar populations (Laevens et al. 2015) to the highest redshift quasars (Bañados et al. 2014).”
SEARCHING FOR DARK MATTER ANNIHILATION IN RECENTLY DISCOVERED MILKY WAY SATELLITES WITH FERMI-LAT (2016, methodology): “…optical imaging surveys and a re-analysis of Sloan Digital Sky Survey (SDSS; York et al. 2000) data revealed more than 20 new satellite systems (Bechtol et al. 2015; Koposov et al. 2015a; Laevens et al. 2015a,b; Kim et al. 2015a; Martin et al. 2015a; Kim & Jerjen 2015; Drlica-Wagner et al. 2015b).”
The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater (2016, background): “For example, it is quite possible that, being the third most massive satellite galaxy, the Sgr dSph (Ibata, Gilmore & Irwin 1994; Niederste-Ostholt et al. 2010) could have had smaller dwarf companions, but only one possible candidate was c© 2015 RAS found in its propinquity (Laevens et al. 2015).”
The Pristine survey - I. Mining the Galaxy for the most metal-poor stars (2017, background): “Satellite discoveries in the SDSS (e.g., Belokurov et al. 2007), Pan-STARRS1 (e.g., Laevens et al. 2015), and the Dark Energy Survey (e.g., Bechtol et al. 2015) have provided us with powerful observational constraints in our cosmic backyard, especially to understand the faint end of galaxy…”
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, background): “…2015; Drlica-Wagner et al. 2016; Torrealba et al. 2018; Koposov et al. 2018; Mau et al. 2020), ATLAS (Torrealba et al. 2016a,b), PanSTARRS1 (PS1; Laevens et al. 2015a,b), and Gaia (Torrealba et al. 2019b) have further increased the sample of confirmed and candidate satellites to more than 50…”
EIGHT ULTRA-FAINT GALAXY CANDIDATES DISCOVERED IN YEAR TWO OF THE DARK ENERGY SURVEY (2015, methodology): “…optical imaging surveys and a reanalysis of SDSS data have resulted in the detection of 14 additional Milky Way companions, tentatively classified as dwarf galaxies (Bechtol et al. 2015; Kim & Jerjen 2015b; Kim et al. 2015a; Koposov et al. 2015a; Laevens et al. 2015a, 2015b; Martin et al. 2015).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “…the positions of the MW GCs (Belokurov et al. 2010; Harris 2010; Muñoz et al. 2012; Balbinot et al. 2013; Kim & Jerjen 2015; Kim et al. 2015, 2016a; Laevens et al. 2015; Luque et al. 2016, 2017; Martin et al. 2016a; Weisz et al. 2016; Koposov et al. 2017; Luque et al. 2018); the M31 satellites…”
CONSTRAINTS ON MACHO DARK MATTER FROM COMPACT STELLAR SYSTEMS IN ULTRA-FAINT DWARF GALAXIES (2016, background): “Where measured, the ages of the stars are consistent with ∼10 Gyr (Bechtol et al. 2015; Laevens et al. 2015).”