First look with JWST spectroscopy: Resemblance among z similar to 8 galaxies and local analogs
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First look with JWST spectroscopy : Resemblance among z similar to 8 galaxies and local analogs. / Schaerer, D.; Marques-Chaves, R.; Barrufet, L.; Oesch, P.; Izotov, Y. I.; Naidu, R.; Guseva, N. G.; Brammer, G.
In: Astronomy & Astrophysics, Vol. 665, L4, 16.09.2022.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - First look with JWST spectroscopy
T2 - Resemblance among z similar to 8 galaxies and local analogs
AU - Schaerer, D.
AU - Marques-Chaves, R.
AU - Barrufet, L.
AU - Oesch, P.
AU - Izotov, Y. I.
AU - Naidu, R.
AU - Guseva, N. G.
AU - Brammer, G.
PY - 2022/9/16
Y1 - 2022/9/16
N2 - Deep images and near-IR spectra of galaxies in the field of the lensing cluster SMACS J0723.3-7327 were recently taken as part of the Early Release Observations (EROs) program of the James Webb Space Telescope (JWST). Among these, two NIRSpec spectra of galaxies, at z = 7.7 and at z = 8.5, were obtained, revealing, for the first time, the rest-frame optical emission line spectra of galaxies in the epoch of reionization, including the detection of the important [O III]lambda 4363 auroral line (see JWST PR 2022-035). We present an analysis of the emission line properties of these galaxies, finding that these galaxies have a high excitation (as indicated by high ratios of [O III]lambda 5007/[O II] lambda 3727, [Ne III] lambda 3869/[O II] lambda 3727), strong [O III]lambda 4363, high equivalent widths, and other properties typical of low-metallicity star-forming galaxies. Using the direct method, we determined oxygen abundances of 12 + log(O/H)approximate to 7.9 in two z = 7.7 galaxies and a lower metallicity of 12 + log(O/H)approximate to 7.4 - 7.5 (similar to 5% solar) in the z = 8.5 galaxy using different strong line methods. More accurate metallicity determinations will require better data. With stellar masses estimated from spectral energy distribution (SED) fits, we find that the three galaxies lie close to or below the z similar to 2 mass-metallicity relation. Overall, these first galaxy spectra at z similar to 8 show a strong resemblance in their the emission line properties of galaxies in the epoch of reionization with those of relatively rare local analogs previously studied with the SDSS. Clearly, the first JWST observations demonstrate already the incredible power of spectroscopy to reveal the properties of galaxies in the early Universe.
AB - Deep images and near-IR spectra of galaxies in the field of the lensing cluster SMACS J0723.3-7327 were recently taken as part of the Early Release Observations (EROs) program of the James Webb Space Telescope (JWST). Among these, two NIRSpec spectra of galaxies, at z = 7.7 and at z = 8.5, were obtained, revealing, for the first time, the rest-frame optical emission line spectra of galaxies in the epoch of reionization, including the detection of the important [O III]lambda 4363 auroral line (see JWST PR 2022-035). We present an analysis of the emission line properties of these galaxies, finding that these galaxies have a high excitation (as indicated by high ratios of [O III]lambda 5007/[O II] lambda 3727, [Ne III] lambda 3869/[O II] lambda 3727), strong [O III]lambda 4363, high equivalent widths, and other properties typical of low-metallicity star-forming galaxies. Using the direct method, we determined oxygen abundances of 12 + log(O/H)approximate to 7.9 in two z = 7.7 galaxies and a lower metallicity of 12 + log(O/H)approximate to 7.4 - 7.5 (similar to 5% solar) in the z = 8.5 galaxy using different strong line methods. More accurate metallicity determinations will require better data. With stellar masses estimated from spectral energy distribution (SED) fits, we find that the three galaxies lie close to or below the z similar to 2 mass-metallicity relation. Overall, these first galaxy spectra at z similar to 8 show a strong resemblance in their the emission line properties of galaxies in the epoch of reionization with those of relatively rare local analogs previously studied with the SDSS. Clearly, the first JWST observations demonstrate already the incredible power of spectroscopy to reveal the properties of galaxies in the early Universe.
KW - galaxies: high-redshift
KW - dark ages, reionization, first stars
KW - galaxies: ISM
KW - EMISSION-LINE GALAXIES
KW - STAR-FORMING GALAXIES
KW - O III EMITTERS
KW - PHOTON PRODUCTION
KW - EVOLUTION
KW - SDSS
KW - I.
U2 - 10.1051/0004-6361/202244556
DO - 10.1051/0004-6361/202244556
M3 - Journal article
VL - 665
JO - Astronomy & Astrophysics
JF - Astronomy & Astrophysics
SN - 0004-6361
M1 - L4
ER -
ID: 320649664