High-Resolution Mass Models of Dwarf Galaxies From Little Things

Abstract

We present high-resolution rotation curves and mass models of 26 dwarf galaxies from "Local Irregulars That Trace Luminosity Extremes, The H I Nearby Galaxy Survey" (LITTLE THINGS). LITTLE THINGS is a high-resolution (∼6″ angular; <2.6 km s −1 velocity resolution) Very Large Array H I survey for nearby dwarf galaxies in the local volume within 11 Mpc. The high-resolution H I observations enable us to derive reliable rotation curves of the sample galaxies in a homogeneous and consistent manner. The rotation curves are then combined with Spitzer archival 3.6 μm and ancillary optical U, B, and V images to construct mass models of the galaxies. This high quality multi-wavelength data set significantly reduces observational uncertainties and thus allows us to examine the mass distribution in the galaxies in detail. We decompose the rotation curves in terms of the dynamical contributions by baryons and dark matter (DM) halos, and compare the latter with those of dwarf galaxies from THINGS as well as ΛCDM Smoothed Particle Hydrodynamic (SPH) simulations in which the effect of baryonic feedback processes is included. Being generally consistent with THINGS and simulated dwarf galaxies, most of the LITTLE THINGS sample galaxies show a linear increase of the rotation curve in their inner regions, which gives shallower logarithmic inner slopes α of their DM density profiles. The mean value of the slopes of the 26 LITTLE THINGS dwarf galaxies is α = − ± 0.32 0.24 which is in accordance with the previous results found for low surface brightness galaxies (α = − ± 0.2 0.2) as well as the seven THINGS dwarf galaxies (α = − ± 0.29 0.07). However, this significantly deviates from the cusp-like DM distribution predicted by DM-only ΛCDM simulations. Instead our results are more in line with the shallower slopes found in the ΛCDM SPH simulations of dwarf galaxies in which the effect of baryonic feedback processes is included. In addition, we discuss the central DM distribution of DDO 210 whose stellar mass is relatively low in our sample to examine the scenario of inefficient supernova feedback in low mass dwarf galaxies predicted from recent ΛCDM SPH simulations of dwarf galaxies where central cusps still remain.

Breathing Fire: How Stellar Feedback Drives Radial Migration, Rapid Size Fluctuations, and Population Gradients in Low-Mass Galaxies

“…The transfer of energy from gas outflows/inflows to collisionless particles is well-studied in the context of the "core-cusp" (Moore 1994;Oh et al 2015) and related "too-bigto-fail" (Boylan- Kolchin et al 2011;Jiang & van den Bosch 2015) problems, which express the discrepancy between the steep central density profiles ("cusps") predicted by ΛCDM models and and the flatter density profiles ("cores") observed in many nearby low-mass galaxies. Recently, a number of studies (for example, Read & Gilmore 2005;Governato et al 2012;Di Cintio et al 2014;Chan et al 2015;Oñorbe et al 2015) have shown that including stellar feedback in simulations can significantly alter dwarf galaxies' density profiles, removing dark matter from the central regions and potentially reconciling the predictions of ΛCDM models with observations, at least for galaxies with M star =10 7−9.6 M e (M halo ≈10 10−11.5 M e ).…”

Under pressure: quenching star formation in low-mass satellite galaxies via stripping

“…Recognizing current uncertainties in the dark matter density profiles of low-mass galaxies (e.g. Moore 1994;de Blok et al 2001;Boylan-Kolchin, Bullock & Kaplinghat 2011, 2012, we also employ mass profiles derived from dynamical modeling of the observed HI kinematics for a subset of our systems, including NFW fits to the THINGS and Little THINGS samples from de Blok et al (2008) and Oh et al (2015) as well as fits to a Burkert profile (Burkert 1995) from Pace (2016).…”

“…In particular, we utilize the NFW fits to the THINGS and Little THINGS velocity fields from de Blok et al (2008) Oh et al 2015) and to a Burkert profile (Pace 2016). As in Fig.…”

Constraining the Nature of Dark Matter with the Star-formation History of the Faintest Local Group Dwarf Galaxy Satellites

“…While the 50% criterion might seem the most sensible and representative, we note that collapse redshift refers to the halo while the SFH refers to the baryons. Since it is conceivable that the baryonic component of the galaxy assembles in the inner region of the subhalo, and since even present-day field dwarf galaxies appear to reside within a few percent of the virial radius of the halo (e.g., Oh et al 2015), it is equally reasonable to argue in favor of the 4% criterion as more representative because most of the halo mass can be gathered later than the assembly of the baryonic galaxy.…”