Аннотация
We present the first spectroscopic measurement of multiple rest-frame optical
emission lines at $z>4$. During the MOSFIRE Deep Evolution Field (MOSDEF)
survey, we observed the galaxy GOODSN-17940 with the Keck I/MOSFIRE
spectrograph. The K-band spectrum of GOODSN-17940 includes significant
detections of the OII$łambda3726,3729$, NeIII$łambda3869$, and
H$\gamma$ emission lines and a tentative detection of H$\delta$, indicating
$z_spec=4.4121$. GOODSN-17940 is an actively star-forming $z>4$ galaxy
based on its K-band spectrum and broadband spectral energy distribution. A
significant excess relative to the surrounding continuum is present in the
Spitzer/IRAC channel 1 photometry of GOODSN-17940, due primarily to strong
H$\alpha$ emission with a rest-frame equivalent width of
$EW(H\alpha)=1200$ \AA. Based on the assumption of $0.5 Z_ødot$
models and the Calzetti attenuation curve, GOODSN-17940 is characterized by
$M_*=510^9 M_ødot$. The Balmer decrement inferred from
H$\alpha$/H$\gamma$ is used to dust correct the H$\alpha$ emission, yielding
$SFR(H\alpha)=320 M_ødot yr^-1$. These $M_*$ and SFR values
place GOODSN-17940 an order of magnitude in SFR above the $z4$
star-forming "main sequence." Finally, we use the observed ratio of
NeIII/OII to estimate the nebular oxygen abundance in GOODSN-17940, finding
$O/H0.2 (O/H)_ødot$. Combining our new NeIII/OII
measurement with those from stacked spectra at $z0, 2, and 3$, we
show that GOODSN-17940 represents an extension to $z>4$ of the evolution
towards higher NeIII/OII (i.e., lower $O/H$) at fixed stellar mass.
It will be possible to perform the measurements presented here out to $z\sim
10$ using the James Webb Space Telescope.
Описание
[1707.05331] The MOSDEF Survey: First Measurement of Nebular Oxygen Abundance at $z>4$
Линки и ресурсы
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