Evidence That Hydra I Is a Tidally Disrupting Milky Way Dwarf Galaxy

Hargis, Jonathan R.; Kimmig, Brian; Willman, Beth; Caldwell, Nelson; Walker, Matthew G.; Strader, Jay; Sand, David J.; Grillmair, Carl J.; Yoon, Joo Heon

doi:10.3847/0004-637x/818/1/39

Cited by 8 publications

(7 citation statements)

References 91 publications

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“…3. Luminosity-metallicity relation for dwarf galaxies in the Cen A group (crosses, triangles, squares; Rejkuba et al 2006;Crnojević et al 2010Crnojević et al , 2011bCrnojević et al , 2019Müller et al 2019b) and Local Group (black dots, McConnachie 2012, from the updated online catalog, and are compiled from different sources, for example from Bellazzini et al 2004;Martin et al 2009;Correnti et al 2009;Kirby et al 2013;Torrealba et al 2016;Hargis et al 2016;Muñoz et al 2018). The dwarfs from this work are indicated as red dots.…”

Section: Properties Of the Stellar Populationsmentioning

confidence: 99%

The properties of dwarf spheroidal galaxies in the Cen A group

Müller

Fahrion

Rejkuba

et al. 2021

A&A

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Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the Local Group, but their low luminosity and surface brightness make similar work in more distant galaxy groups challenging. Modern instrumentation unlocks the possibility of scrutinizing these faint systems in other environments, expanding the parameter space of group properties. We use MUSE spectroscopy to study the properties of 14 known or suspected dSph satellites of Cen A. Twelve targets are confirmed to be group members based on their radial velocities. Two targets are background galaxies at ∼50 Mpc: KK 198 is a face-on spiral galaxy, and dw1315-45 is an ultradiffuse galaxy with an effective radius of ∼2300 pc. The 12 confirmed dSph members of the Cen A group have old and metal-poor stellar populations and follow the stellar metallicity-luminosity relation defined by the dwarf galaxies in the Local Group. In the three brightest dwarf galaxies (KK 197, KKs 55, and KKs 58), we identify globular clusters, as well as a planetary nebula in KK 197, although its association with this galaxy and/or the extended halo of Cen A is uncertain. Using four discrete tracers, we measure the velocity dispersion and dynamical mass of KK 197. This dSph appears dark matter dominated and lies on the radial acceleration relation of star-forming galaxies within the uncertainties. It also is consistent with predictions stemming from modified Newtonian dynamics (MOND). Surprisingly, in the dwarf KK 203 we find an extended Hα ring. Careful examination of Hubble Space Telescope photometry reveals a very low level of star formation at ages between 30-300 Myr. The Hα emission is most likely linked to a ∼40 Myr old supernova remnant, although other possibilities for its origin cannot be entirely ruled out.

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Section: Properties Of the Stellar Populationsmentioning

confidence: 99%

The properties of dwarf spheroidal galaxies in the Cen A group

Müller

Fahrion

Rejkuba

et al. 2021

A&A

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“…Crater I; Kirby et al 2015;Voggel et al 2016). We also do not consider overdensities that are thought to be tidally disrupting dwarf galaxies: Boötes III (Carlin et al 2009;Carlin & Sand 2018), Canis Major (Martin et al 2004), and Hydra I (Hargis et al 2016). Furthermore, we restrict our analysis to satellites which have published line-of-sight velocities in order to have full 6-D kinematic information.…”

Section: Proper Motionsmentioning

confidence: 99%

The velocity anisotropy of the Milky Way satellite system

Riley

Fattahi

Pace

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We analyse the orbital kinematics of the Milky Way (MW) satellite system utilizing the latest systemic proper motions for 38 satellites based on data from Gaia Data Release 2. Combining these data with distance and line-of-sight velocity measurements from the literature, we use a likelihood method to model the velocity anisotropy, β, as a function of Galactocentric distance and compare the MW satellite system with those of simulated MW-mass haloes from the APOSTLE and Auriga simulation suites. The anisotropy profile for the MW satellite system increases from β ∼ −2 at r ∼ 20 kpc to β ∼ 0.5 at r ∼ 200 kpc, indicating that satellites closer to the Galactic centre have tangentially-biased motions while those farther out have radiallybiased motions. The motions of satellites around APOSTLE host galaxies are nearly isotropic at all radii, while the β(r) profiles for satellite systems in the Auriga suite, whose host galaxies are substantially more massive in baryons than those in APOSTLE, are more consistent with that of the MW satellite system. This shape of the β(r) profile may be attributed to the central stellar disc preferentially destroying satellites on radial orbits, or intrinsic processes from the formation of the Milky Way system.

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“…Indeed, Grillmair (2011) suggested that a relatively high surface density, double-lobed feature found along the stream -called Hydra I -could be the dwarf galaxy or globular cluster progenitor of the stream. However, while the shallow SDSS imaging assumed an old, metal-poor stellar population, deeper imaging and spectroscopy of Hydra I by Hargis et al (2016) , which is only slightly more metal-poor than the thick disc ([Fe/H] ∼ −0.7, e.g Gilmore & Wyse 1985). It is clear that a kinematic exploration of the anti-centre region is desperately needed to dissect these complex structures.…”

Section: Introductionmentioning

confidence: 99%

Cresting the wave: proper motions of the Eastern Banded Structure

Deason

Belokurov

Koposov

2017

Monthly Notices of the Royal Astronomical Society

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We study the kinematic properties of the Eastern Banded Structure (EBS) and Hydra I overdensity using exquisite proper motions derived from the Sloan Digital Sky Survey (SDSS) and Gaia source catalog. Main sequence turn-off stars in the vicinity of the EBS are identified from SDSS photometry; we use the proper motions and, where applicable, spectroscopic measurements of these stars to probe the kinematics of this apparent stream. We find that the EBS and Hydra I share common kinematic and chemical properties with the nearby Monoceros Ring. In particular, the proper motions of the EBS, like Monoceros, are indicative of prograde rotation (V φ ∼ 180 − 220 km s −1 ), which is similar to the Galactic thick disc. The kinematic structure of stars in the vicinity of the EBS suggest that it is not a distinct stellar stream, but rather marks the "edge" of the Monoceros Ring. The EBS and Hydra I are the latest substructures to be linked with Monoceros, leaving the Galactic anti-centre a mess of interlinked overdensities which likely share a unified, Galactic disc origin.

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Evidence That Hydra I Is a Tidally Disrupting Milky Way Dwarf Galaxy

Cited by 8 publications

References 91 publications

The properties of dwarf spheroidal galaxies in the Cen A group

The properties of dwarf spheroidal galaxies in the Cen A group

The velocity anisotropy of the Milky Way satellite system

Cresting the wave: proper motions of the Eastern Banded Structure

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