Quiescent or dusty? Unveiling the nature of extremely red galaxies at $z>3$
L. Barrufet, P. Oesch, R. Marques-Chaves, K. Arellano-Cordova, J. F. W. Baggen, A. C. Carnall, F. Cullen, J. S. Dunlop, R. Gottumukkala, Y. Fudamoto, G. D. Illingworth, D. Magee, R. J. McLure, D. J. Leod, M. J. Micha{l}owski, M. Stefanon, P. G. van Dokkum, A. Weibel
arXiv:2404.08052v1 Announce Type: new
Abstract: The advent of the JWST has revolutionised our understanding of high-redshift galaxies. In particular, the NIRCam instrument on-board JWST has revealed a population of Hubble Space Telescope (HST)-dark galaxies that had previously evaded optical detection, potentially due to significant dust obscuration, quiescence, or simply extreme redshift. Here, we present the first NIRSpec spectra of 23 HST-dark galaxies ($mathrm{H-F444W>1.75}$), unveiling their nature and physical properties. This sample includes both dusty and quiescent galaxies with spectroscopic data from NIRSpec/PRISM, providing accurate spectroscopic redshifts with $mathrm{overline{z}_{spec} = 4.1 pm 0.7}$. The spectral features demonstrate that, while the majority of HST-dark galaxies are dusty, a substantial fraction, $mathrm{13^{+9}_{-6} %}$, are quiescent. For the dusty galaxies, we have quantified the dust attenuation using the Balmer decrement ($mathrm{Halpha / Hbeta}$), finding attenuations $mathrm{A_{V} > 2 mag}$. We find that HST-dark dusty galaxies are $mathrm{Halpha}$ emitters with equivalent widths spanning the range $mathrm{ 68 A 9.8}$. This pilot NIRSpec program reveals the diverse nature of HST-dark galaxies and highlights the effectiveness of NIRSpec/PRISM spectroscopic follow-up in distinguishing between dusty and quiescent galaxies and properly quantifying their physical properties. Upcoming research utilising higher-resolution NIRSpec data and combining JWST with ALMA observations will enhance our understanding of these enigmatic and challenging sources.arXiv:2404.08052v1 Announce Type: new
Abstract: The advent of the JWST has revolutionised our understanding of high-redshift galaxies. In particular, the NIRCam instrument on-board JWST has revealed a population of Hubble Space Telescope (HST)-dark galaxies that had previously evaded optical detection, potentially due to significant dust obscuration, quiescence, or simply extreme redshift. Here, we present the first NIRSpec spectra of 23 HST-dark galaxies ($mathrm{H-F444W>1.75}$), unveiling their nature and physical properties. This sample includes both dusty and quiescent galaxies with spectroscopic data from NIRSpec/PRISM, providing accurate spectroscopic redshifts with $mathrm{overline{z}_{spec} = 4.1 pm 0.7}$. The spectral features demonstrate that, while the majority of HST-dark galaxies are dusty, a substantial fraction, $mathrm{13^{+9}_{-6} %}$, are quiescent. For the dusty galaxies, we have quantified the dust attenuation using the Balmer decrement ($mathrm{Halpha / Hbeta}$), finding attenuations $mathrm{A_{V} > 2 mag}$. We find that HST-dark dusty galaxies are $mathrm{Halpha}$ emitters with equivalent widths spanning the range $mathrm{ 68 A 9.8}$. This pilot NIRSpec program reveals the diverse nature of HST-dark galaxies and highlights the effectiveness of NIRSpec/PRISM spectroscopic follow-up in distinguishing between dusty and quiescent galaxies and properly quantifying their physical properties. Upcoming research utilising higher-resolution NIRSpec data and combining JWST with ALMA observations will enhance our understanding of these enigmatic and challenging sources.