Spinning Bar and a Star-formation Inefficient Repertoire: Turbulence in Hickson Compact Group NGC7674. (arXiv:2003.10458v1 [astro-ph.GA])

Spinning Bar and a Star-formation Inefficient Repertoire: Turbulence in Hickson Compact Group NGC7674. (arXiv:2003.10458v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Salim_D/0/1/0/all/0/1">Diane M. Salim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alatalo_K/0/1/0/all/0/1">Katherine Alatalo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Federrath_C/0/1/0/all/0/1">Christoph Federrath</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Groves_B/0/1/0/all/0/1">Brent Groves</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kewley_L/0/1/0/all/0/1">Lisa J. Kewley</a>

The physics regulating star formation (SF) in Hickson Compact Groups (HCG)
has thus far been difficult to describe, due to their unique kinematic
properties. In this study we expand upon previous works to devise a more
physically meaningful SF relation able to better encompass the physics of these
unique systems. We combine CO(1–0) data from the Combined Array from Research
in Millimeter Astronomy (CARMA) to trace the column density of molecular gas
$Sigma_mathrm{gas}$ and deep H$alpha$ imaging taken on the Southern
Astrophysical Research (SOAR) Telescope tracing $Sigma_mathrm{SFR}$ to
investigate star formation efficiency across face-on HCG, NGC7674. We find a
lack of universality in star formation, with two distinct sequences present in
the $Sigma_mathrm{gas}-Sigma_mathrm{SFR}$ plane; one for inside and one for
outside the nucleus. We devise a SF relation based on the multi-freefall nature
of gas and the critical density, which itself is dependent on the virial
parameter $alpha_{mathrm{vir}}$, the ratio of turbulent to gravitational
energy. We find that our modified SF relation fits the data and describes the
physics of this system well with the introduction of a virial parameter of
about 5–10 across the galaxy. This $alpha_{mathrm{vir}}$ leads to an
order-of-magnitude reduction in SFR compared to $alpha_{mathrm{vir}}approx
1$ systems.

The physics regulating star formation (SF) in Hickson Compact Groups (HCG)
has thus far been difficult to describe, due to their unique kinematic
properties. In this study we expand upon previous works to devise a more
physically meaningful SF relation able to better encompass the physics of these
unique systems. We combine CO(1–0) data from the Combined Array from Research
in Millimeter Astronomy (CARMA) to trace the column density of molecular gas
$Sigma_mathrm{gas}$ and deep H$alpha$ imaging taken on the Southern
Astrophysical Research (SOAR) Telescope tracing $Sigma_mathrm{SFR}$ to
investigate star formation efficiency across face-on HCG, NGC7674. We find a
lack of universality in star formation, with two distinct sequences present in
the $Sigma_mathrm{gas}-Sigma_mathrm{SFR}$ plane; one for inside and one for
outside the nucleus. We devise a SF relation based on the multi-freefall nature
of gas and the critical density, which itself is dependent on the virial
parameter $alpha_{mathrm{vir}}$, the ratio of turbulent to gravitational
energy. We find that our modified SF relation fits the data and describes the
physics of this system well with the introduction of a virial parameter of
about 5–10 across the galaxy. This $alpha_{mathrm{vir}}$ leads to an
order-of-magnitude reduction in SFR compared to $alpha_{mathrm{vir}}approx
1$ systems.

http://arxiv.org/icons/sfx.gif

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