Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

Li, T. S.; Simon, Joshua D.; Drlica-Wagner, A.; Bechtol, K.; Wang, M. Y.; García-Bellido, J.; Frieman, Joshua A.; Marshall, J. L.; James, D. J.; Strigari, Louis E.; Pace, Andrew B.; Balbinot, E.; Zhang, Y.; Abbott, T. M. C.; Allam, S.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; Costa, L. N. da; DePoy, D. L.; Desai, S.; Diehl, H. T.; Eifler, T. F.; Flaugher, B.; Goldstein, D.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutiérrez, G.; Krause, E.; Kuêhn, K.; Lin, H.; Maia, M. A. G.; March, M.; Menanteau, F.; Miquel, R.; Plazas, A. A.; Romer, A. K.; Sánchez, E.; Santiago, B.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Sobreira, F.; Suchyta, E.; Tarlè, G.; Thomas, Daniel; Tucker, D. L.; Walker, A. R.; Wechsler, Risa H.; Wester, W.; Yanny, B.

doi:10.3847/1538-4357/aa6113

Cited by 153 publications

(164 citation statements)

References 95 publications

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“…The GC has a CMD that is similar to its host galaxy, i.e. dominated by an old (∼10 Gyr) and metal-poor ([Fe/H] ∼ -2.5) stellar population Li et al (2017). confirmed the low metallicity finding [Fe/H] = -2.38 and measured a velocity dispersion of 6.9 km/s Crnojević et al (2016).…”

supporting

confidence: 61%

Extending the globular cluster system–halo mass relation to the lowest galaxy masses

Forbes

Read

Gieles

et al. 2018

Monthly Notices of the Royal Astronomical Society

139

123

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High mass galaxies, with halo masses M 200 ≥ 10 10 M , reveal a remarkable near-linear relation between their globular cluster (GC) system mass and their host galaxy halo mass. Extending this relation to the mass range of dwarf galaxies has been problematic due to the difficulty in measuring independent halo masses. Here we derive new halo masses based on stellar and HI gas kinematics for a sample of nearby dwarf galaxies with GC systems. We find that the GC system mass-halo mass relation for galaxies populated by GCs holds from halo masses of M 200 ∼ 10 14 M down to below M 200 ∼ 10 9 M , although there is a substantial increase in scatter towards low masses. In particular, three well-studied ultra diffuse galaxies, with dwarf-like stellar masses, reveal a wide range in their GC-to-halo mass ratios. We compare our GC systemhalo mass relation to the recent model of El Badry et al., finding that their fiducial model does not reproduce our data in the low mass regime. This may suggest that GC formation needs to be more efficient than assumed in their model, or it may be due to the onset of stochastic GC occupation in low mass halos. Finally, we briefly discuss the stellar mass-halo mass relation for our low mass galaxies with GCs, and we suggest some nearby dwarf galaxies for which searches for GCs may be fruitful. Hudson et al. (2014), using weak lensing results from the CFHTLenS survey and the database of GC systems from Harris et al. (2013), were able to extend the relation down to stellar masses of M * ∼10 8 M . They measured a GC system mass to halo mass ratio of 4 (× 10 −5 )

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supporting

confidence: 61%

Extending the globular cluster system–halo mass relation to the lowest galaxy masses

Forbes

Read

Gieles

et al. 2018

Monthly Notices of the Royal Astronomical Society

139

123

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“…11 We transformed from DES-g, r to V mag using equation (2) of 0.2 Å added in quadrature. This systematic uncertainty is derived by checking the EWs from the repeated measurements (Li et al 2017), in a similar way as described in Section 4.1. The metallicity uncertainties are calculated from the uncertainties on the CaT EWs and the uncertainties on the calibration parameters from Carrera et al (2013).…”

Section: Cat Metallicitymentioning

confidence: 99%

The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science

Koposov

Zucker

et al. 2019

Monthly Notices of the Royal Astronomical Society

107

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We introduce the Southern Stellar Stream Spectroscopy Survey (S 5 ), an on-going program to map the kinematics and chemistry of stellar streams in the Southern Hemisphere. The initial focus of S 5 has been spectroscopic observations of recently identified streams within the footprint of the Dark Energy Survey (DES), with the eventual goal of surveying streams across the entire southern sky. Stellar streams are composed of material that has been tidally striped from dwarf galaxies and globular clusters and hence are excellent dynamical probes of the gravitational potential of the Milky Way, as well as providing a detailed snapshot of its accretion history. Observing with the 3.9-m Anglo-Australian Telescope's 2-degree-Field fibre positioner and AAOmega spectrograph, and combining the precise photometry of DES DR1 with the superb proper motions from Gaia DR2, allows us to conduct an efficient spectroscopic survey to map these stellar streams. So far S 5 has mapped 9 DES streams and 3 streams outside of DES; the former are the first spectroscopic observations of these recently discovered streams. In addition to the stream survey, we use spare fibres to undertake a Milky Way halo survey and a low-redshift galaxy survey. This paper presents an overview of the S 5 program, describing the scientific motivation for the survey, target selection, observation strategy, data reduction and survey validation. Finally, we describe early science results on stellar streams and Milky Way halo stars drawn from the survey. Updates on S 5 , including future public data release, can be found at http://s5collab.github.io.

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“…Such LG galaxies are typically resolved into individual stars and their discovery relies on special methods based on searching for overdensities after filtering stars with isochrone masks (see, e.g., Koposov et al 2008 LG field galaxy, Eri II, has an effective surface brightness below 10 6 L /kpc 2 . Eri II was discovered relatively recently and is located just outside 300 kpc from the MW (Li et al 2017). The relative lack of LSB galaxies in the LG field suggests that most missing dwarfs are low surface brightness systems whose discovery and identification will be challenging.…”

Section: Missing Dwarfs In the Local Groupmentioning

confidence: 99%

The missing dwarf galaxies of the Local Group

Fattahi

Navarro

Frenk

2020

Monthly Notices of the Royal Astronomical Society

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We study the Local Group (LG) dwarf galaxy population using cosmological simulations of volumes selected to resemble the surroundings of the Milky Way (MW) and Andromeda (M31) galaxies. The simulations, from the APOSTLE project, indicate that the total mass within 3 Mpc of the pair's midpoint (M 3Mpc ) typically exceeds ∼ 3 times the sum of the virial masses of the two primaries and that the dwarf galaxy formation efficiency per unit mass is uniform throughout the volume. This suggests that MW and M31 satellites should make up fewer than one third of all LG dwarfs within 3 Mpc. This is consistent with the fraction (28 per cent) of galaxies with stellar mass M * > 10 7 M that are satellites. In addition, the total number of such galaxies (42) suggests, for the APOSTLE galaxy mass-halo mass relation, a total LG mass of M 3Mpc ∼ 10 13 M . At lower galaxy masses, however, the satellite fraction is substantially higher (42 per cent for M * > 10 5 M , or 42 out of 99). If this is due to incompleteness in the field sample, then ∼ 50 dwarf galaxies at least as massive as the Draco dwarf spheroidal are missing from our current LG field dwarf inventory. The incompleteness interpretation is supported by the pronounced flattening of the LG luminosity function below M * ∼ 10 7 M , and by the scarcity of low-surface brightness LG field galaxies: whereas ∼ 40 per cent of all M * > 10 5 M MW/M31 satellites have effective surface brightness below Σ eff = 26.5 m V /arcsec 2 , only 1 out of all field dwarfs does. The simulations indicate that most missing dwarfs should lie near the virial boundaries of the two LG primaries, and predict a trove of nearby dwarfs that await discovery by upcoming wide-field imaging surveys.

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Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

Cited by 153 publications

References 95 publications

Extending the globular cluster system–halo mass relation to the lowest galaxy masses

Extending the globular cluster system–halo mass relation to the lowest galaxy masses

The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science

The missing dwarf galaxies of the Local Group

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