skip to main content

Title: Robust H i kinematics of gas-rich ultra-diffuse galaxies: hints of a weak-feedback formation scenario
ABSTRACT We study the gas kinematics of a sample of six isolated gas-rich low surface brightness galaxies, of the class called ultra-diffuse galaxies (UDGs). These galaxies have recently been shown to be outliers from the baryonic Tully–Fisher relation (BTFR), as they rotate much slower than expected given their baryonic mass, and to have a baryon fraction similar to the cosmological mean. By means of a 3D kinematic modelling fitting technique, we show that the H i in our UDGs is distributed in ‘thin’ regularly rotating discs and we determine their rotation velocity and gas velocity dispersion. We revisit the BTFR adding galaxies from other studies. We find a previously unknown trend between the deviation from the BTFR and the exponential disc scale length valid for dwarf galaxies with circular speeds ≲ 45 km s−1, with our UDGs being at the extreme end. Based on our findings, we suggest that the high baryon fractions of our UDGs may originate due to the fact that they have experienced weak stellar feedback, likely due to their low star formation rate surface densities, and as a result they did not eject significant amounts of gas out of their discs. At the same time, we find indications that more » our UDGs may have higher-than-average stellar specific angular momentum, which can explain their large optical scale lengths. « less
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Award ID(s):
1714828 1637339
Publication Date:
NSF-PAR ID:
10167229
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
495
Issue:
4
Page Range or eLocation-ID:
3636 to 3655
ISSN:
0035-8711
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    ABSTRACT We present the first set of cosmological baryonic zoom-in simulations of galaxies including dissipative self-interacting dark matter (dSIDM). These simulations utilize the Feedback In Realistic Environments galaxy formation physics, but allow the dark matter to have dissipative self-interactions analogous to standard model forces, parametrized by the self-interaction cross-section per unit mass, (σ/m), and the dimensionless degree of dissipation, 0 < fdiss < 1. We survey this parameter space, including constant and velocity-dependent cross-sections, and focus on structural and kinematic properties of dwarf galaxies with $M_{\rm halo} \sim 10^{10-11}{\, \rm M_\odot }$ and $M_{\ast } \sim 10^{5-8}{\, \rm M_\odot }$.more »Central density profiles (parametrized as ρ ∝ rα) of simulated dwarfs become cuspy when $(\sigma /m)_{\rm eff} \gtrsim 0.1\, {\rm cm^{2}\, g^{-1}}$ (and fdiss = 0.5 as fiducial). The power-law slopes asymptote to α ≈ −1.5 in low-mass dwarfs independent of cross-section, which arises from a dark matter ‘cooling flow’. Through comparisons with dark matter only simulations, we find the profile in this regime is insensitive to the inclusion of baryons. However, when $(\sigma /m)_{\rm eff} \ll 0.1\, {\rm cm^{2}\, g^{-1}}$, baryonic effects can produce cored density profiles comparable to non-dissipative cold dark matter (CDM) runs but at smaller radii. Simulated galaxies with $(\sigma /m) \gtrsim 10\, {\rm cm^{2}\, g^{-1}}$ and the fiducial fdiss develop significant coherent rotation of dark matter, accompanied by halo deformation, but this is unlike the well-defined thin ‘dark discs’ often attributed to baryon-like dSIDM. The density profiles in this high cross-section model exhibit lower normalizations given the onset of halo deformation. For our surveyed dSIDM parameters, halo masses and galaxy stellar masses do not show appreciable difference from CDM, but dark matter kinematics and halo concentrations/shapes can differ.« less
  2. The Pisces-Perseus Supercluster (PPS) offers a convenient, accessible environment for the study of large scale structure in the local universe. The Arecibo Pisces-Perseus Supercluster Survey (APPSS) seeks to observe the infall of galaxies toward the main filament of the PPS which is nearly perpendicular to our line of sight. Tracing such infall reveals valuable information about the gravitational field - and thus mass distribution - of the PPS. However, obtaining accurate measurements of such deviation from smooth Hubble flow requires redshift-independent distance measurements. The baryonic Tully-Fisher relation (BTFR) offers an appealing solution in the distance regime of the PPS, butmore »while the high-mass end of this relation boasts a tight correlation, the low-mass end - where the APPSS sample lies - shows considerably more scatter. We use the magnetohydrodynamical simulations of IllustrisTNG to examine a template BTFR in an attempt to better understand the error budget of, and identify systematic scatter within, the BTFR as it corresponds to the APPSS sample of galaxies. We find the low mass scatter of the simulated BTFR to be populated predominantly by highly gas dominated, low surface brightness galaxies with colors less blue than typical. This unusually quiescent subset of galaxies appears to share systematically inefficient star formation, with very high gas depletion timescales that deviate rapidly from an otherwise gradual trend apparent throughout the rest of the galaxy population. This subset of inefficiently star forming galaxies tends to decrease the slope of the BTFR at low masses, an effect that lies in contrast to the steepening of the BTFR generally expected in this mass regime. Further work is needed to determine if this collection of galaxies is physically motivated or is instead a finite resolution effect of the simulation. This work is supported by NSF/AST-1714828 to MPH.« less
  3. ABSTRACT We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5 and 108.6 M⊙. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flattermore »gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady ‘puffing’ of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the ‘puffing’ process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.« less
  4. ABSTRACT We present a study of the stellar host galaxy, CO (1–0) molecular gas distribution and AGN emission on 50–500 pc-scales of the gravitationally lensed dust-obscured AGN MG J0751+2716 and JVAS B1938+666 at redshifts 3.200 and 2.059, respectively. By correcting for the lensing distortion using a grid-based lens modelling technique, we spatially locate the different emitting regions in the source plane for the first time. Both AGN host galaxies have 300–500 pc-scale size and surface brightness consistent with a bulge/pseudo-bulge, and 2 kpc-scale AGN radio jets that are embedded in extended molecular gas reservoirs that are 5–20 kpc in size. The CO (1–0) velocity fields showmore »structures possibly associated with discs (elongated velocity gradients) and interacting objects (off-axis velocity components). There is evidence for a decrement in the CO (1–0) surface brightness at the location of the host galaxy, which may indicate radiative feedback from the AGN, or offset star formation. We find CO–H2 conversion factors of around αCO = 1.5 ± 0.5 (K km s−1 pc2)−1, molecular gas masses of >3 × 1010 M⊙, dynamical masses of ∼1011 M⊙, and gas fractions of around 60 per cent. The intrinsic CO line luminosities are comparable to those of unobscured AGN and dusty star-forming galaxies at similar redshifts, but the infrared luminosities are lower, suggesting that the targets are less efficient at forming stars. Therefore, they may belong to the AGN feedback phase predicted by galaxy formation models, because they are not efficiently forming stars considering their large amount of molecular gas.« less
  5. To create a Baryonic Tully-Fisher Relationship (BTFR) for the ALFALFA galaxies, we require a corresponding catalog of optical photometry to produce reliable stellar masses to complement their HI masses. Different methods of calculating stellar mass have been used in derivations of the BTFR depending on the sky distribution, prior redshift information or multiwavelength photometry of the sample galaxies. In order to obtain stellar masses for all of the ALFALFA galaxies in the SDSS photometric footprint, we use a crossmatch file between the α-100 catalog and the SDSS DR14 database to produce a reliable catalog of optical photometric properties for usemore »in the stellar mass calculation and inclination-dependent corrections. For the stellar masses, we use the methodology set forth in Taylor et al. (2011), specifically, the modeled mass to light ratio estimated from the g-i color index. In order to compare stellar masses derived in this way with results obtained by other authors in the literature who used Petrosian and Sersic masses available in the NASA Sloan Atlas (NSA) to derive stellar masses, we investigate the differences in stellar mass and the corrections for inclination and extinction between values complied in the NSA and ones obtained using our α-100-SDSS cross-match. We investigate systematic differences in stellar mass estimates based on photometric properties such as color, surface brightness and concentration and on others such as distance, velocity width and HI richness. This research is supported by the Brinson Foundation for the Arecibo Pieces-Perseus Supercluster Survey (APPSS) and NSF grant NSF/AST-1714828 to M.P. Haynes.« less