Characterizing the Infall Times and Quenching Timescales of Milky Way Satellites with $Gaia$ Proper Motions
Year: 2019
Type: preprint
Abstract: Observations of low-mass satellite galaxies in the nearby Universe point towards a strong dichotomy in their star-forming properties relative to systems with similar mass in the field. Specifically, satellite galaxies are preferentially gas poor and no longer forming stars, while their field counterparts are largely gas rich and actively forming stars. Much of the recent work to understand this dichotomy has been statistical in nature, determining not just that environmental processes are most likely responsible for quenching these low-mass systems but also that they must operate very quickly after infall onto the host system, with quenching timescales $\lesssim 2~ {\rm Gyr}$ at ${M}_{\star} \lesssim 10^{8}~{\rm M}_{\odot}$. This work utilizes the newly-available $Gaia$ DR2 proper motion measurements along with the Phat ELVIS suite of high-resolution, cosmological, zoom-in simulations to study low-mass satellite quenching around the Milky Way on an object-by-object basis. We derive constraints on the infall times for $37$ of the known low-mass satellite galaxies of the Milky Way, finding that $\gtrsim~70\%$ of the `classical' satellites of the Milky Way are consistent with the very short quenching timescales inferred from the total population in previous works. The remaining classical Milky Way satellites have quenching timescales noticeably longer, with $τ_{\rm quench} \sim 6 - 8~{\rm Gyr}$, highlighting how detailed orbital modeling is likely necessary to understand the specifics of environmental quenching for individual satellite galaxies. Additionally, we find that the $6$ ultra-faint dwarf galaxies with publicly available $HST$-based star-formation histories are all consistent with having their star formation shut down prior to infall onto the Milky Way -- which, combined with their very early quenching times, strongly favors quenching driven by reionization.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: The Physics of Satellite Galaxy Quenching: Novel Analysis of Observations, and High-Resolution Simulations, Collaborative Research: The GOGREEN Survey - Caring about the Environment, Collaborative Research: Hydrodynamic Simulations of the Local Group, Collaborative Research: CDS&E: Mining Physically Predictive Cosmological Simulations, CAREER: The Faint Frontier of Galaxy Formation, G407823349, G433322167, G4518818167, Collaborative Research: M31 Satellites Past and Present, AS THE FAINTEST LOWEST-LUMINOSITY AND MOST DARK-MATTER-DOMINATED EXTREMES OF THE GALAXY POPULATION DWARF GALAXIES PRESENT UNIQUE OPPORTUNITIES FOR STUDYING GALAXY FORMATION AND THE PROPERTIES OF DARK. ACCORDINGLY THEY HAVE BEEN OBSERVED IN DETAIL FROM THE GROUND AND (BY NASA MISSIONS) FROM SPACE WITH THE HOPES OF UNRAVELING HOW DWARF GALAXIES FORM THE EFFECTS OF REIONIZATION ON GALAXY FORMATION AND WHETHER SIGNATURES OF THE PARTICLE NATURE OF DARK MATTER (DM) INTERACTIONS CAN BE OBSERVED. SUCH WORK HAS GAINED INIMPORTANCE AS EFFORTS TO DIRECTLY DETECT DM HAVE SO FAR YIELDED ONLY UPPER LIMITS TO THE INTERACTION BETWEEN DM AND NORMAL MATTER LEAVING ASTROPHYSICAL TESTS AS THE PRIMARY MEANS OF INVESTIGATING THE NATURE OF DM. WE PROPOSE TO UNDERTAKE AN EXTENSIVE YET FOCUSED PROGRAM OF COSMOLOGICAL HYDRODYNAMIC SIMULATIONS AIMED AT UNDERSTANDING THEFORMATION OF DWARF GALAXIES. WE WILL FOCUS ON THE INTERPLAY BETWEEN GALAXY FORMATION AND DARK MATTER IN THESE GALAXIES POINTING TOWARD SPECIFIC OBSERVABLES TO DISENTANGLE THE EFFECTS OF GALAXY FORMATION PHYSICS FROM THE EFFECTS OF DM PHYSICS. OUR SIMULATION SUITE WILL EXPLORE COLLISIONLESS COLD DARK MATTER (CDM) AND BROAD CLASSES OF ALTERNATIVES WHERE DM HAS A NON-NEGLIGIBLE FREE-STREAMING LENGTH AND / OR SELF-SCATTERING CROSS SECTION. THE NOVEL ASPECTS OF THE PROPOSED WORK WILL INCLUDE: (1) A MODERN TREATMENT OF BARYONIC PHYSICS USING GIZMO A NEW CODE THAT USES ACCURATE MESHLESS METHODS FOR HYDRODYNAMICS (2) FEEDBACK IN REALISTIC ENVIRONMENTS (FIRE) A SUITE OF GALAXY FORMATION PARAMETRIZATIONS WITH WELL-TESTED EXPLICIT IMPLEMENTATIONS OF STELLAR FEEDBACK (3) AN EXPLORATION OF REALISTIC MODELS OF DM BEYOND CDM BASED ON AN EFFECTIVE THEORY OF STRUCTURE FORMATION WITH FULL BARYONIC PHYSICS AND (4) DETAILEDMOCK OBSERVATIONS OF THE SIMULATIONS IN ORDER TO IDENTIFY SPECIFIC DISTINGUISHING TESTS FOR CDM AND ITS ALTERNATIVES.OUR RESEARCH WILL PROVIDE A FRAMEWORK WITHIN WHICH ASTROPHYSICAL INFERENCES ABOUT THE NATURE OF DM CAN BE FAIRLY AND SELFCONSISTENTLY TESTED. CRUCIALLY WE WILL EXPLORE UNCERTAIN ASPECTS OF GALAXY FORMATION AND DM PHYSICS IN A CONTROLLED MANNER FOCUSING ON THE HALO MASS RANGE -- 9.5<LOG10(M/M_SUN)<10.5 -- WHERE CURRENT MODELS ARE MOST UNCERTAIN. THIS WILL MARK A MAJOR EFFORT TOSYSTEMATICALLY STUDY DIFFERENT DM MODELS COMBINED WITH REALISTIC TREATMENTS OF GALAXY FORMATION PHYSICS THAT ARE IMPLEMENTED IN AN IDENTICAL WAY FOR THE VARIOUS DM MODELS. THE RESULTS OF THE PROPOSED RESEARCH WILL BE DRAMATIC IMPROVEMENTS IN THE UNDERSTANDING OF HOW BARYONIC VERSUS DM PHYSICS AFFECT ASTROPHYSICAL OBSERVABLES. SUCH A STUDY IS VERY TIMELY AS OBSERVATIONS OF DWARF GALAXIES IN ANDBEYOND THE LOCAL GROUP HAVE PROGRESSED SUBSTANTIALLY IN RECENT YEARS WITH NEW REVELATIONS ABOUT DWARFS' DM CONTENT STAR FORMATION HISTORIES AND STELLAR METALLICITIES CHALLENGING PREVIOUS INTERPRETATIONS., CAREER: The Ties that (Un)Bind: Understanding the Connection Between Galaxies, Stars, and Black Holes, G58316358, G6273510985, THE ORIGIN OF THE STELLAR INITIAL MASS FUNCTION IMF IS ONE OF THE OLDEST PROBLEMS IN THEORETICAL ASTROPHYSICS, AND ONE OF THE MOST PROFOUND. THIS DIS, Absorption-line Gas: Combining Models and Observations, G8398842341
OpenAlex ID: W2950533859