In:
Publications of the Astronomical Society of Japan, Oxford University Press (OUP), Vol. 53, No. 3 ( 2001-06-25), p. 459-468
Abstract:
We present low-resolution, near-IR JHK spectra of the weak $z=2.39$ radio galaxy 53W002, obtained with the OH-airglow Suppressor spectrograph (OHS) and Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru Telescope. They cover rest-frame wavelengths of 3400–7200$Å$, and the emission lines of [O II]$\lambda$3727, H$\beta$, [O III] $\lambda\lambda$4959, 5007, H$\alpha$, [N II]$\lambda\lambda$6548, 6583 and [S II] $\lambda\lambda$6716, 6731 were detected. Using the H$\alpha$/H$\beta$ line ratio, we find an extinction of $E(B\hbox{--}V)=0.14$. The emission-line ratios are reproduced by a cloud of electron density $n_{\mathrm{e}}=1\times 10^{3-4}\,\mathrm{cm}^{-3}$ with solar metallicity, ionized by an $\alpha=-0.7$ power-law continuum with ionizing parameter $U=1\times 10^{-3}$. In addition to these emission lines, we make the first spectroscopic confirmation of the Balmer discontinuity in a high-$z$ radio galaxy. Together with rest-frame UV photometry from the literature, we show that at least 1/3 of the present stellar mass was formed in the current starburst. The stellar mass was estimated to be $(1\hbox{--}1.4)\times10^{11}\,{{{M}_{\odot}}}$ by one-component model fitting, which is smaller than that of typical $z\sim 1$ B2/6C radio galaxies. We suggest that 53W002 is currently assembling a large part of its stellar mass through merger events with the surrounding sub-galactic clumps, some of which can be identified with the L$\alpha$ emitters detected in narrow-band imaging. After a few such events over the next few Gyr, 53W002 will evolve into a massive elliptical galaxy.
Type of Medium:
Online Resource
ISSN:
2053-051X
,
0004-6264
DOI:
10.1093/pasj/53.3.459
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2001
detail.hit.zdb_id:
2206640-8
detail.hit.zdb_id:
2083084-1
SSG:
16,12
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