24 research outputs found
Effects of Stellar Feedback on Stellar and Gas Kinematics of Star-forming Galaxies at 0.6 < z < 1.0
Recent zoom-in cosmological simulations have shown that stellar feedback can flatten the inner density profile of the dark matter halo in low-mass galaxies. A correlation between the stellar/gas velocity dispersion (σ_(star), σ_(gas)) and the specific star formation rate (sSFR) is predicted as an observational test of the role of stellar feedback in re-shaping the dark matter density profile. In this work we test the validity of this prediction by studying a sample of star-forming galaxies at 0.6 < z < 1.0 from the LEGA-C survey, which provides high signal-to-noise measurements of stellar and gas kinematics. We find that a weak but significant correlation between σ_(star) (and σ_(gas)) and sSFR indeed exists for galaxies in the lowest mass bin (M_* ~ 10¹⁰ M_⊙). This correlation, albeit with a ~35% scatter, holds for different tracers of star formation, and becomes stronger with redshift. This result generally agrees with the picture that at higher redshifts star formation rate was generally higher, and galaxies at M_* ≾ 10¹⁰ M_⊙ have not yet settled into a disk. As a consequence, they have shallower gravitational potentials more easily perturbed by stellar feedback. The observed correlation between σ_(star) (and σ_(gas)) and sSFR supports the scenario predicted by cosmological simulations, in which feedback-driven outflows cause fluctuations in the gravitation potential that flatten the density profiles of low-mass galaxies
Disentangling the physical origin of emission line ratio offsets at high redshift with spatially resolved spectroscopy
We present spatially resolved Hubble Space Telescope grism spectroscopy of 15
galaxies at drawn from the DEEP2 survey. We analyze H+[N
II], [S II] and [S III] emission on kpc scales to explore which mechanisms are
powering emission lines at high redshifts, testing which processes may be
responsible for the well-known offset of high redshift galaxies from the
locus in the [O III]/H versus [N II]/H BPT
(Baldwin-Phillips-Terlevich) excitation diagram. We study spatially resolved
emission line maps to examine evidence for active galactic nuclei (AGN),
shocks, diffuse ionized gas (DIG), or escaping ionizing radiation, all of which
may contribute to the BPT offsets observed in our sample. We do not find
significant evidence of AGN in our sample and quantify that, on average, AGN
would need to contribute 25% of the H flux in the central
resolution element in order to cause the observed BPT offsets. We find weak
() evidence of DIG emission at low surface brightnesses, yielding an
implied total DIG emission fraction of 20%, which is not significant
enough to be the dominant emission line driver in our sample. In general we
find that the observed emission is dominated by star forming H II regions. We
discuss trends with demographic properties and the possible role of
-enhanced abundance patterns in the emission spectra of high redshift
galaxies. Our results indicate that photo-ionization modeling with stellar
population synthesis inputs is a valid tool to explore the specific star
formation properties which may cause BPT offsets, to be explored in future
work.Comment: 27 pages, 26 figures. Accepted to Ap
Spectroscopic Mimicry for the Protonated Retinal Schiff Base in vivo with Modified Amphiphilic Clay Interlayers as a Possible Model of Opsin Environment
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The OSIRIS Lens-amplified Survey (OLAS). I. Dynamical Effects of Stellar Feedback in Low-mass Galaxies at z ∼ 2
We introduce the OSIRIS Lens-Amplified Survey (OLAS), a kinematic survey of gravitationally lensed galaxies at cosmic noon taken with Keck adaptive optics. In this paper, we present spatially resolved spectroscopy and nebular emission kinematic maps for 17 star-forming galaxies with stellar masses 8 < log(M ∗/M o) < 9.8 and redshifts 1.2 < z < 2.3. OLAS is designed to probe the stellar mass (M ∗) and specific star formation rate (sSFR) range where simulations suggest that stellar feedback is most effective at driving gaseous outflows that create galaxy-wide potential fluctuations, which can generate dark matter cores. We compare our kinematic data with the trend among sSFR, M ∗, and Hα velocity dispersion, σ, from the Feedback In Realistic Environments (FIRE) simulations. Our observations reveal a correlation between sSFR and σ at fixed M ∗ that is similar to the trend predicted by simulations: feedback from star formation drives star-forming gas and newly formed stars into more dispersion-dominated orbits. The observed magnitude of this effect is in good agreement with the FIRE simulations, in which feedback alters the central density profiles of low-mass galaxies, converting dark matter cusps into cores over time. Our data support the scenario that stellar feedback drives gaseous outflows and potential fluctuations, which in turn drive dark matter core formation in dwarf galaxies