Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc

Popis výsledku v původním jazyce

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 &lt;= 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.

Název v anglickém jazyce

Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc

Popis výsledku anglicky

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 &lt;= 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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

—

Návaznosti

S - Specificky vyzkum na vysokych skolach

Rok uplatnění

2018

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

e-ISSN

—

Svazek periodika

477

Číslo periodika v rámci svazku

4

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

14

Strana od-do

5554-5567

Kód UT WoS článku

000435630100093

EID výsledku v databázi Scopus

2-s2.0-85052493205