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29 March 2024 |
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Article overview
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The spatially resolved star formation relation in two HI-rich galaxies with central post-starburst signature | Anne Klitsch
; Martin A. Zwaan
; Harald Kuntschner
; Warrick J. Couch
; Michael B. Pracy
; | Date: |
23 Nov 2016 | Abstract: | E+A galaxies are post-starburst systems that are identified from their
optical spectra. These galaxies contain a substantial young A-type stellar
component, but have only little ongoing star formation (SF). HI 21-cm line
emission is found in approximately half of the nearby E+A galaxies, indicating
that they contain a reservoir of gas that could fuel active SF. Here, we study
two HI-rich galaxies, which show a typical E+A spectrum at the centre and SF at
larger radii. We present new high spatial resolution radio interferometric
observations of the HI 21-cm emission line using the VLA and of the CO(1-0)
emission line using ALMA. We combine these data sets to predict the SFR and
show that it does not correlate well with the SFR derived from H alpha on
sub-kpc scales. We apply a recently developed statistical model for the small
scale behaviour of the SF relation to predict and interpret the observed
scatter. We find smoothly distributed, regularly rotating HI gas. The CO(1-0)
emission line is not detected for both galaxies. The derived upper limit on the
CO mass implies a molecular gas depletion time shorter than 20 Myr. However,
due to the low metallicity, the CO-to-H2 conversion factor is highly uncertain.
In the relations between the H alpha-based SFR and the HI mass, we observe a
substantial scatter we demonstrate results from small-number statistics of
independent star-forming regions on sub-kpc scales. This finding adds to the
existing literature reporting a scale dependence of the molecular SF relation,
showing that the atomic and molecular phases are both susceptible to the
evolutionary ’cycling’ of individual regions. This suggests that the atomic gas
reservoirs host substantial substructure, which should be observable with
future high-resolution observations. (abridged) | Source: | arXiv, 1611.7672 | Services: | Forum | Review | PDF | Favorites |
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