The UV spectral slope beta and stellar population of most active star-forming galaxies at z~4. (arXiv:1904.01373v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yamanaka_S/0/1/0/all/0/1">Satoshi Yamanaka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yamada_T/0/1/0/all/0/1">Toru Yamada</a>
We investigate the stellar population of star-forming galaxies at $z sim 4$
by focusing on their slope of rest-frame ultraviolet (UV) continuum, $beta$
where $f_{lambda} propto lambda^{beta}$. We investigate the sample of
bright Lyman Break Galaxies (LBGs) with $i’ leq 26.0$ in the Subaru/XMM-Newton
Deep Survey field by using the SED fitting analysis. We find that the
apparently redder ($beta_{mathrm{obs}} > -1.73$) LBGs tend to be dusty
($mathrm{Av} > 1.0$), have the young stellar population ($beta_{mathrm{int}}
< -2.42$), and the intrinsically active star-forming galaxies (SFR $gtrsim$ a
few $times 10^{2}$ $mathrm{M_{odot}} mathrm{yr^{-1}}$). It means that a
significant fraction of the UV-selected LBGs at $z sim 4$ is on-going active
and dust obscured star-forming galaxies. We compare the IR to UV luminosity
ratio assuming the dust attenuation laws with the sub-millimeter observations
from previous works. The result suggests that the Calzetti-like dust
attenuation law is preferable for the active and dusty star-forming LBGs at $z
= 4$. We also find that an extrapolation of the
$beta_{mathrm{int}}$-$M_{mathrm{UV,int}}$ relation toward the fainter
magnitude range below our sample magnitude limit intersects the
$beta_{mathrm{obs}}$-$M_{mathrm{UV,obs}}$ relation previously obtained in
the deeper narrow-area observations at $M_{mathrm{UV}} = -18.9$ and $beta =
-1.94$, which coincides with the break point of
$beta_{mathrm{obs}}$-$M_{mathrm{UV,obs}}$ relation observed so far. The
coincidence suggest that we see the almost dust-free population at
$M_{mathrm{UV,obs}} gtrsim -18.9$.
We investigate the stellar population of star-forming galaxies at $z sim 4$
by focusing on their slope of rest-frame ultraviolet (UV) continuum, $beta$
where $f_{lambda} propto lambda^{beta}$. We investigate the sample of
bright Lyman Break Galaxies (LBGs) with $i’ leq 26.0$ in the Subaru/XMM-Newton
Deep Survey field by using the SED fitting analysis. We find that the
apparently redder ($beta_{mathrm{obs}} > -1.73$) LBGs tend to be dusty
($mathrm{Av} > 1.0$), have the young stellar population ($beta_{mathrm{int}}
< -2.42$), and the intrinsically active star-forming galaxies (SFR $gtrsim$ a
few $times 10^{2}$ $mathrm{M_{odot}} mathrm{yr^{-1}}$). It means that a
significant fraction of the UV-selected LBGs at $z sim 4$ is on-going active
and dust obscured star-forming galaxies. We compare the IR to UV luminosity
ratio assuming the dust attenuation laws with the sub-millimeter observations
from previous works. The result suggests that the Calzetti-like dust
attenuation law is preferable for the active and dusty star-forming LBGs at $z
= 4$. We also find that an extrapolation of the
$beta_{mathrm{int}}$-$M_{mathrm{UV,int}}$ relation toward the fainter
magnitude range below our sample magnitude limit intersects the
$beta_{mathrm{obs}}$-$M_{mathrm{UV,obs}}$ relation previously obtained in
the deeper narrow-area observations at $M_{mathrm{UV}} = -18.9$ and $beta =
-1.94$, which coincides with the break point of
$beta_{mathrm{obs}}$-$M_{mathrm{UV,obs}}$ relation observed so far. The
coincidence suggest that we see the almost dust-free population at
$M_{mathrm{UV,obs}} gtrsim -18.9$.
http://arxiv.org/icons/sfx.gif
