33 research outputs found
Size-scaling of clump instabilities in turbulent, feedback regulated disks
We explore the scaling between the size of star-forming clumps and rotational
support in massively star-forming galactic disks. The analysis relies on
simulations of a clumpy galaxy at and the observed DYNAMO sample of rare
clumpy analogs at to test a predictive clump size scaling
proposed by \citet{Fisher2017ApJ...839L...5F} in the context of the Violent
Disk Instability (VDI) theory. We here determine the clump sizes using a
recently presented 2-point estimator, which is robust against resolution/noise
effects, hierarchical clump substructure, clump-clump overlap and other
galactic substructure. After verifying Fisher's clump scaling relation for the
DYNAMO observations, we explore whether this relation remains characteristic of
the VDI theory, even if realistic physical processes, such as local asymetries
and stellar feedback, are included in the model. To this end, we rely on
hydrodynamic zoom-simulations of a Milky Way-mass galaxy with four different
feedback prescriptions. We find that, during its marginally stable epoch at
, this mock galaxy falls on the clump scaling relation, although its
position on this relation depends on the feedback model. This finding implies
that Toomre-like stability considerations approximately apply to large
() instabilities in marginally stable turbulent disks,
irrespective of the feedback model, but also emphasizes that the global clump
distribution of a turbulent disk depends strongly on feedback.Comment: Accepted by ApJ, no changes made. 11 pages, 4 figure
Dynamic equilibrium sets atomic content of galaxies across cosmic time
We analyze 88 independent high-resolution cosmological zoom-in simulations of
disk galaxies in the NIHAO simulations suite to explore the connection between
the atomic gas fraction and angular momentum of baryons throughout cosmic time.
The study is motivated by the analytic model of \citet{obreschkow16}, which
predicts a relation between the atomic gas fraction and the
global atomic stability parameter , where and
are the mass and specific angular momentum of the galaxy (stars+cold gas) and
is the velocity dispersion of the atomic gas. We show that the
simulated galaxies follow this relation from their formation () to
present within dex. To explain this behavior, we explore the
evolution of the local Toomre stability and find that -- of the
atomic gas in all simulated galaxies is stable at any time. In other words,
throughout the entire epoch of peak star formation until today, the timescale
for accretion is longer than the timescale to reach equilibrium, thus resulting
in a quasi-static equilibrium of atomic gas at any time. Hence, the evolution
of depends on the complex hierarchical growth history primarily
via the evolution of . An exception are galaxies subject to strong
environmental effects.Comment: 12 pages, 7 figures; accepted to Ap
DUVET Survey: Mapping Outflows in the Metal-Poor Starburst Mrk 1486
We present a method to characterize star-formation driven outflows from
edge-on galaxies and apply this method to the metal-poor starburst galaxy, Mrk
1486. Our method uses the distribution of emission line flux (from H and
[OIII] 5007) to identify the location of the outflow and measure the extent
above the disk, the opening angle, and the transverse kinematics. We show that
this simple technique recovers a similar distribution of the outflow without
requiring complex modelling of line-splitting or multi-Gaussian components, and
is therefore applicable to lower spectral resolution data. In Mrk 1486 we
observe an asymmetric outflow in both the location of the peak flux and total
flux from each lobe. We estimate an opening angle of depending
on the method and assumptions adopted. Within the minor axis outflows, we
estimate a total mass outflow rate of M yr, which
corresponds to a mass loading factor of . We observe a non-negligible
amount of flux from ionized gas outflowing along the edge of the disk
(perpendicular to the biconical components), with a mass outflow rate
M yr. Our results are intended to demonstrate a method that
can be applied to high-throughput, low spectral resolution observations, such
as narrow band filters or low spectral resolution IFS that may be more able to
recover the faint emission from outflows.Comment: 12 Pages, 6 Figure
Unveiling the complex circumgalactic medium: a comparative study of merging and non-interacting galaxy groups
A giant galaxy in the young Universe with a massive ring
In the local (redshift z~0) Universe, collisional ring galaxies make up only
~0.01% of galaxies and are formed by head-on galactic collisions that trigger
radially propagating density waves. These striking systems provide key
snapshots for dissecting galactic disks and are studied extensively in the
local Universe. However, not much is known about distant (z>0.1) collisional
rings. Here we present a detailed study of a ring galaxy at a look-back time of
10.8 Gyr (z=2.19). Compared with our Milky Way, this galaxy has a similar
stellar mass, but has a stellar half-light radius that is 1.5-2.2 times larger
and is forming stars 50 times faster. The large, diffuse stellar light outside
the star-forming ring, combined with a radial velocity on the ring and an
intruder galaxy nearby, provides evidence for this galaxy hosting a collisional
ring. If the ring is secularly evolved, the implied large bar in a giant disk
would be inconsistent with the current understanding of the earliest formation
of barred spirals. Contrary to previous predictions, this work suggests that
massive collisional rings were as rare 11 Gyr ago as they are today. Our
discovery offers a unique pathway for studying density waves in young galaxies,
as well as constraining the cosmic evolution of spiral disks and galaxy groups.Comment: Author's version for the main article (10 pages). The Supplementary
Information (22 pages) and a combined pdf are provided here
http://astronomy.swin.edu.au/~tyuan/paper Published version available online
http://dx.doi.org/10.1038/s41550-020-1102-