ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOÖTES I DWARF SPHEROIDAL GALAXY

By Sergey E. Koposov, G. Gilmore, M. Walker, V. Belokurov, N. Evans II, M. Fellhauer, W. Gieren, D. Geisler, L. Monaco, J. Norris and 5 more. 2011

135 citations recorded by the source corpus.

We develop, implement, and characterize an enhanced data reduction approach which delivers precise, accurate, radial velocities from moderate resolution spectroscopy with the fiber-fed VLT/FLAMES+GIRAFFE facility. This facility, with appropriate care, delivers radial velocities adequate to resolve the intrinsic velocity dispersions of the very faint dwarf spheroidal (dSph) galaxies. Importantly, repeated measurements let us reliably calibrate our individual velocity errors (0.2 kms−1 ⩽ δV ⩽ 5 km s−1) and directly detect stars with variable radial velocities. We show, by application to the Boötes I dSph, that the intrinsic velocity dispersion of this system is significantly below 6.5 km s−1 reported by previous studies. Our data favor a two-population model of Boötes I, consisting of a majority “cold” stellar component, with velocity dispersion 2.4+0.9− 0.5 km s−1, and a minority “hot” stellar component, with velocity dispersion ∼9 km s−1, although we cannot completely rule out a single component distribution with velocity dispersion 4.60.8− 0.6 km s−1. We speculate that this complex velocity distribution actually reflects the distribution of velocity anisotropy in Boötes I, which is a measure of its formation processes.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2814a662ef604bd5aef0f24e68089cc58559857b

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Citations in the corpus

DWARF GALAXY ANNIHILATION AND DECAY EMISSION PROFILES FOR DARK MATTER EXPERIMENTS (2014, methodology): “The observing strategy of Koposov et al. (2011) provided ∼ 10 independent velocity measurements of each star over the course of one month, thereby enabling a direct examination of intrinsic velocity variability (e.g., due to unresolved binary stars) that can potentially inflate observed velocity…”
A METHOD FOR MEASURING (SLOPES OF) THE MASS PROFILES OF DWARF SPHEROIDAL GALAXIES (2011, background): “3 − 4 km s−1 that have been measured from fainter stars in some of the least luminous Milky Way satellites (e.g., Martin et al. 2007; Simon & Geha 2007; Adén et al. 2009; Koposov et al. 2011).”
A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM (2013, background): “We plot the velocity dispersions, mass within the half-light radius, and central densities for all M31 (blue circles) and MW (red triangles, Walker et al. 2009b; Adén et al. 2009; Koposov et al. 2011; Simon et al. 2011) dSphs as a function of radius.”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, methodology): “To model the observed spectra and obtain chemical abundances and radial velocities we use a direct pixel-fitting approach by interpolated spectral templates (see e.g. Koleva et al. 2009; Koposov et al. 2011; Walker, Olszewski & Mateo 2015).”
EIGHT ULTRA-FAINT GALAXY CANDIDATES DISCOVERED IN YEAR TWO OF THE DARK ENERGY SURVEY (2015, background): “…follow-up observations (Kleyna et al. 2005; Muñoz et al. 2006; Martin et al. 2007; Simon & Geha 2007; Adén et al. 2009; Belokurov et al. 2009; Carlin et al. 2009; Geha et al. 2009; Koch et al. 2009; Walker et al. 2009; Koposov et al. 2011; Simon et al. 2011; Willman et al. 2011; Kirby et al. 2013).”
EIGHT NEW MILKY WAY COMPANIONS DISCOVERED IN FIRST-YEAR DARK ENERGY SURVEY DATA (2015, background): “…“ultra-faint” galaxies (Kleyna et al. 2005; Muñoz et al. 2006; Martin et al. 2007; Simon & Geha 2007; Adén et al. 2009; Belokurov et al. 2009; Carlin et al. 2009; Geha et al. 2009; Koch et al. 2009; Walker et al. 2009; Koposov et al. 2011; Simon et al. 2011; Willman et al. 2011; Kirby et al. 2013).”
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies (2012, background): “…in detail how the properties of the mass distribution of faint dwarf galaxies can be inferred from their stellar kinematics (Evans et al. 2011; Koposov et al. 2011; Boylan-Kolchin et al. 2011a; Adams et al. 2012) and how interactions with the main galaxy affect the DM, SFHs and final stellar…”
Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, background): “This could be due to systematic uncertainties in the data [230], as we must distinguish between σ ≈ 2 km s−1 and σ ≈ 5 km s−1.”
THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA (2014, background): “We only measure metallicities for two of these velocity outliers, both RGB stars in Boo I with velocities that vary by more than 30 km s−1 from Koposov et al. (2011); the remainder cannot be constrained by our data because of their high temperatures and/or the low SNR of their spectra.”
THE SPLASH SURVEY: SPECTROSCOPY OF 15 M31 DWARF SPHEROIDAL SATELLITE GALAXIES (2011, background): “We also show the MW dSph compilation of Wolf et al. (2010), with updates for Boötes I and Segue 1 from Koposov et al. (2011) and Simon et al. (2011), respectively, as triangles (red).”
The Pristine survey - I. Mining the Galaxy for the most metal-poor stars (2017, methodology): “Stars in this sample that are spectroscopically followed-up by either Norris et al. (2010) or Koposov et al. (2011) are circled in colour if the star is a very likely member of the Boötes I system, as determined by the radial velocity and stellar parameters derived MNRAS 000, 000–000 (0000) from…”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, unknown): “…et al. (2008), 12: Lee et al. (2009), 13: Carrera et al. (2002), 14: Walker et al. (2009b), 15: Dall’Ora et al. (2006), 16: Okamoto et al. (2012), 17: Koposov et al. (2011), 18: Walsh et al. (2008), 19: Koch et al. (2009), 20: Simon & Geha (2007), 21: Greco et al. (2008), 22: Belokurov et al.…”
THE OBSERVED PROPERTIES OF DWARF GALAXIES IN AND AROUND THE LOCAL GROUP (2012, unknown): “…2009; (12) Kim et al. 1998; (13) van der Marel et al. 2002; (14) Brüns et al. 2005; (15) Harris & Zaritsky 2006; (16) Stanimirović et al. 2004; (17) Koposov et al. 2011; (18) Walker et al. 2007; (19) Wilkinson et al. 2004; (20) Walker et al. 2009c; (21) Walker et al. 2009b; (22) Walker et al.…”
Gaia DR2 proper motions of dwarf galaxies within 420 kpc (2018, methodology): “We use two spectroscopic catalogs for this galaxy, from Martin et al. (2007) and Koposov et al. (2011): the former contains binary membership classification and we adopt from that study also the values of the heliocentric l.o.s. systemic velocity (vLOS,sys = 99km/s) and velocity dispersion (5…”
THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT (2013, background): “While binary stars were known to exist in the UFDs based on repeated spectroscopic measurements of red giant branch stars (Simon et al. 2011; Koposov et al. 2011), these observations did not strongly constrain the binary fraction itself (Martinez et al. 2011).”