Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F18%3A10389080" target="_blank" >RIV/00216208:11320/18:10389080 - isvavai.cz</a>
Result on the web
<a href="https://doi.org/10.1093/mnras/sty1006" target="_blank" >https://doi.org/10.1093/mnras/sty1006</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1093/mnras/sty1006" target="_blank" >10.1093/mnras/sty1006</a>
Alternative languages
Result language
angličtina
Original language name
Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc
Original language description
We present optical photometry of Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)/Wide Field Camera (WFC) data of the resolved stellar populations in the outer disc of the dwarf irregular galaxy DDO 154. The photometry reveals that young main sequence (MS) stars are almost absent from the outermost HI disc. Instead, most are clustered near the main stellar component of the galaxy. We constrain the stellar initial mass function (IMF) by comparing the luminosity function of the MS stars to simulated stellar populations, assuming a constant star formation rate over the dynamical time-scale. The best-fitting IMF is deficient in high-mass stars compared to a canonical Kroupa IMF, with a best-fitting slope alpha = -2.45 and upper mass limit M-U = 16M(circle dot). This top-light IMF is consistent with predictions of the integrated galactic IMF theory. Combining the HST images with HI data from The HI Nearby Galaxy Survey (THINGS), we determine the star formation law (SFL) in the outer disc. The fit has a power-law exponent N = 2.92 +/- 0.22 and zero-point A = 4.47 +/- 0.65 x 10(-7) M-circle dot yr(-1) kpc(-2). This is depressed compared to the Kennicutt-Schmidt SFL, but consistent with weak star formation observed in diffuse HI environments. Extrapolating the SFL over the outer disc implies that there could be significant star formation occurring that is not detectable in H alpha. Last, we determine the Toomre stability parameter Q of the outer disc of DDO 154 using the THINGS HI rotation curve and velocity dispersion map. 72 per cent of the HI in our field has Q <= 4 and this incorporates 96 per cent of the observed MS stars. Hence, 28 per cent of the HI in the field is largely dormant.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10308 - Astronomy (including astrophysics,space science)
Result continuities
Project
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Continuities
S - Specificky vyzkum na vysokych skolach
Others
Publication year
2018
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Monthly Notices of the Royal Astronomical Society
ISSN
0035-8711
e-ISSN
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Volume of the periodical
477
Issue of the periodical within the volume
4
Country of publishing house
GB - UNITED KINGDOM
Number of pages
14
Pages from-to
5554-5567
UT code for WoS article
000435630100093
EID of the result in the Scopus database
2-s2.0-85052493205