A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies

Abstract

With a central surface brightness of ${\mu }_0=29.3$ mag. per sq. arcsec, and half-light radius of $r_{\mathrm{half}}=3.1_{-1.1}^{+0.9}$~kpc, Andromeda XIX (And XIX) is an extremely diffuse satellite of Andromeda. We present spectra for $\sim 100$ red giant branch stars in this galaxy, plus 16 stars in a nearby stellar stream. With this exquisite dataset, we re-derive the properties of And XIX, measuring a systemic velocity of $v_r=-109.0\pm 1.6$ km/s and a velocity dispersion of ${\sigma }_v=7.8_{-1.5}^{+1.7}$ km/s (higher than derived in our previous work). We marginally detect a velocity gradient along the major axis of $\mathrm{d}v/\mathrm{d}r=-2.1\pm 1.8$ km/s kpc${}^{-1}$. We find its mass-to-light ratio is higher than galaxies of comparable stellar mass ($[M/L{]}_{\mathrm{half}}=278_{-198}^{+146}{M}_{\odot }/L_{\odot }$), but its dynamics place it in a halo with a similar total mass to these galaxies. This could suggest that And XIX is a "puffed up" dwarf galaxy, whose properties have been altered by tidal processes, similar to its Milky Way counterpart, Antlia II. For the nearby stream, we measure $v_r=-279.2\pm 3.7$ km/s, and ${\sigma }_v=13.8_{-2.6}^{+3.5}$ km/s. We measure its metallicity, and find it to be more metal rich than And XIX, implying that the two features are unrelated. Finally, And XIX's dynamical and structural properties imply it is a local analogue to ultra diffuse galaxies (UDGs). Its complex dynamics suggest that the masses of distant UDGs measured from velocity dispersions alone should be carefully interpreted

15 pages, (plus 5 extra for appendices), 15 figures, MNRAS accepted (no significant revision from previous version)

References in corpus (29)

• The Dartmouth Stellar Evolution Database
• Astrophysics Source Code Library
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster
• Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies
• NIHAO XI: Formation of Ultra-Diffuse Galaxies by outflows
• A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• A second galaxy missing dark matter in the NGC1052 group
• The PAndAS view of the Andromeda satellite system - II. Detailed properties of 23 M31 dwarf spheroidal galaxies
• A trio of new Local Group galaxies with extreme properties
• Still Missing Dark Matter: KCWI High-Resolution Stellar Kinematics of NGC1052-DF2
• The abundance of ultra-diffuse galaxies from groups to clusters: UDGs are relatively more common in more massive haloes
• The Dragonfly Nearby Galaxies Survey. II. Ultra diffuse galaxies near the elliptical galaxy NGC 5485
• A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs
• The nearest ultra diffuse galaxy: UGC2162
• Halo mass estimates from the Globular Cluster populations of 175 Low Surface Brightness Galaxies in the Fornax Cluster
• Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG
• The evolution of ultra-diffuse galaxies in nearby galaxy clusters from the Kapteyn IAC WEAVE INT Clusters Survey ($\text{KIWICS}$)
• Leo V: Spectroscopy of a Distant and Disturbed Satellite
• Comparing the observable properties of dwarf galaxies on and off the Andromeda plane
• Metallicity Evolution of the Six Most Luminous M31 Dwarf Satellites
• A Suprime-Cam study of the stellar population of Ursa Major I dwarf spheroidal galaxy
• Spectroscopy of the three distant Andromedan satellites Cassiopeia III, Lacerta I, and Perseus I
• Comparing M31 and Milky Way Satellites: The Extended Star Formation Histories of Andromeda II and Andromeda XVI
• Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V
• Stellar Substructures around the Hercules Dwarf Spheroidal Galaxy
• Evidence of Absence of Tidal Features in the Outskirts of Ultra Diffuse Galaxies in the Coma Cluster
• Exploding Satellites -- The Tidal Debris of the Ultra-Faint Dwarf Galaxy Hercules

Cited by in corpus (7)

• Kinematics of Antlia 2 and Crater 2 from The Southern Stellar Stream Spectroscopic Survey (S5)
• Observational constraints on stellar feedback in dwarf galaxies
• Flattened structures of dwarf satellites around massive host galaxies in the MATLAS low-to-moderate density fields
• The Nature of Ultra-diffuse Galaxies in Distant Massive Galaxy Clusters: Abell 370 in the Hubble Frontier Fields
• Keck Spectroscopy of the Coma Cluster Ultra-Diffuse Galaxy Y358: Dynamical Mass in a Wider Context
• A detailed star formation history for the extremely diffuse Andromeda XIX dwarf galaxy
• Galactic tides and the Crater II dwarf spheroidal: a challenge to LCDM?