Tracing the outer disk of NGC 300: An ultraviolet view. (arXiv:1907.06366v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mondal_C/0/1/0/all/0/1">Chayan Mondal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Subramaniam_A/0/1/0/all/0/1">Annapurni Subramaniam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+George_K/0/1/0/all/0/1">Koshy George</a>
We present an ultra-violet (UV) study of the galaxy NGC~300 using GALEX
far-UV (FUV) and near-UV (NUV) observations. We studied the nature of UV
emission in the galaxy and correlated it with optical, H~I and mid-infrared
(3.6 $mu$m) wavelengths. Our study identified extended features in the outer
disk, with the UV disk extending up to radius 12 kpc ($>$2R$_{25})$. We
estimated the FUV and NUV disk scale-length as 3.05$pm$0.27 kpc and
2.66$pm$0.20 kpc respectively. The scale-length in FUV is 2.3 times larger
than that at 3.6 $mu$m, and we also find the disk to gradually become flatter
from longer to shorter wavelengths. We performed a statistical source
subtraction to eliminate the background contaminants and identified 261
unresolved UV sources between the radii 5.3 kpc and 10 kpc (1 $sim$ 2
R$_{25}$). The identified UV sources show an age range between 1 – 300 Myr with
a peak at 25 Myr and a mass range between $10^3 M_{odot}$ to $10^6 M_{odot}$,
estimated using starburst99 models. The north-eastern spiral arm is found to be
populated by young low mass sources suggesting that the star formation in this
spiral arm is a recent phenomenon. The UV emission beyond the R$_{25}$ radius
has contribution from these low mass sources and is extended up to $sim$
2R$_{25}$ radius. We conclude that NGC~300 has an extended UV disk, mainly
populated by young low mass sources. The star formation rate is measured to be
$sim$0.46 $M_{odot}/yr$ which is comparable to its near optical twin M33.
We present an ultra-violet (UV) study of the galaxy NGC~300 using GALEX
far-UV (FUV) and near-UV (NUV) observations. We studied the nature of UV
emission in the galaxy and correlated it with optical, H~I and mid-infrared
(3.6 $mu$m) wavelengths. Our study identified extended features in the outer
disk, with the UV disk extending up to radius 12 kpc ($>$2R$_{25})$. We
estimated the FUV and NUV disk scale-length as 3.05$pm$0.27 kpc and
2.66$pm$0.20 kpc respectively. The scale-length in FUV is 2.3 times larger
than that at 3.6 $mu$m, and we also find the disk to gradually become flatter
from longer to shorter wavelengths. We performed a statistical source
subtraction to eliminate the background contaminants and identified 261
unresolved UV sources between the radii 5.3 kpc and 10 kpc (1 $sim$ 2
R$_{25}$). The identified UV sources show an age range between 1 – 300 Myr with
a peak at 25 Myr and a mass range between $10^3 M_{odot}$ to $10^6 M_{odot}$,
estimated using starburst99 models. The north-eastern spiral arm is found to be
populated by young low mass sources suggesting that the star formation in this
spiral arm is a recent phenomenon. The UV emission beyond the R$_{25}$ radius
has contribution from these low mass sources and is extended up to $sim$
2R$_{25}$ radius. We conclude that NGC~300 has an extended UV disk, mainly
populated by young low mass sources. The star formation rate is measured to be
$sim$0.46 $M_{odot}/yr$ which is comparable to its near optical twin M33.
http://arxiv.org/icons/sfx.gif
