Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Alex J. Cameron
Aayush Saxena
Andrew J. Bunker
Francesco D'Eugenio
Stefano Carniani
Roberto Maiolino
Emma Curtis-Lake
Pierre Ferruit
Peter Jakobsen
Santiago Arribas
Nina Bonaventura
Stephane Charlot
Jacopo Chevallard
Mirko Curti
Tobias J. Looser
Michael V. Maseda
Tim Rawle
Bruno Rodríguez Del Pino
Renske Smit
Hannah Übler
Abstract： We present emission line ratios from a sample of 26 Lyman break galaxies from
$z\sim5.5-9.5$ with $-17.0
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Andrew J. Bunker
Aayush Saxena
Alex J. Cameron
Chris J. Willott
Emma Curtis-Lake
Peter Jakobsen
Stefano Carniani
Renske Smit
Roberto Maiolino
Joris Witstok
Mirko Curti
Francesco D'Eugenio
Gareth C. Jones
Pierre Ferruit
Santiago Arribas
Stephane Charlot
Jacopo Chevallard
Giovanna Giardino
Anna de Graaff
Tobias J. Looser
Abstract： We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate $z>10$ Lyman break galaxy in the GOODS-North field with $M_{UV}=-21.5$. We derive a redshift of $z=10.603$ (lower than previous determinations) based on multiple emission lines in our low and medium resolution spectra over $0.8-5.3\,\mu$m. We significantly detect the continuum and measure a blue rest-UV spectral slope of $\beta=-2.4$. Remarkably, we see spatially-extended Lyman-$\alpha$ in emission (despite the highly-neutral IGM expected at this early epoch), offset 555 km/s redward of the systemic redshift. From our measurements of collisionally-excited lines of both low- and high-ionization (including [O II] $\lambda3727$, [Ne III] $\lambda 3869$ and C III] $\lambda1909$) we infer a high ionization parameter ($\log U\sim -2$). We detect the rarely-seen N IV] $\lambda1486$ and N III]$\lambda1748$ lines in both our low and medium resolution spectra, with other high ionization lines seen in low resolution spectrum such as He II (blended with O III]) and C IV (with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionization from AGN. The high C III]/He II ratios, however, suggest a likely star-formation explanation. If the observed emission lines are powered by star formation, then the strong N III] $\lambda1748$ observed may imply an unusually high $N/O$ abundance. Balmer emission lines (H$\gamma$, H$\delta$) are also detected, and if powered by star formation rather than an AGN we infer a star formation rate of $\sim 20-30 M_{\odot}\,\rm yr^{-1}$ (depending on the IMF) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Aayush Saxena
Brant E. Robertson
Andrew J. Bunker
Ryan Endsley
Alex J. Cameron
Stephane Charlot
Charlotte Simmonds
Sandro Tacchella
Joris Witstok
Chris Willott
Stefano Carniani
Emma Curtis-Lake
Pierre Ferruit
Peter Jakobsen
Santiago Arribas
Jacopo Chevallard
Mirko Curti
Francesco D'Eugenio
Anna De Graaff
Gareth C. Jones
Abstract： We report the discovery of a remarkable Ly$\alpha$ emitting galaxy at $z=7.278$, JADES-GS+53.16746-27.7720 (shortened to JADES-GS-z7-LA), with EW$_0$(Ly$\alpha$) $\approx400 \pm 90$A and UV magnitude $-16.7$. The spectroscopic redshift is confirmed via rest-frame optical lines [O II], H$\beta$ and [O III] in its JWST/NIRSpec Micro-Shutter Assembly (MSA) spectrum. The Ly$\alpha$ line is detected in both lower resolution ($R\sim100$) PRISM as well as medium resolution ($R\sim1000$) G140M grating spectra. The Ly$\alpha$ FWHM in the grating is $\approx360$ km s$^{-1}$ and the line peaks within $120$ km s$^{-1}$ of the systemic redshift, indicative of very little neutral gas or dust within the galaxy. We estimate the Ly$\alpha$ escape fraction to be $\sim100\%$. JADES-GS-z7-LA has a [O III]/[O II] ratio (O32) of $8.8 \pm 1.1$ and ([O III]+[O II])/H$\beta$ ratio (R23) of $9.6\pm2.2$, consistent with low metallicity and high ionization parameters. Deep NIRCam imaging also revealed a close companion source (separated by $0.23''$), which exhibits similar photometry to that of JADES-GS-z7-LA, with a photometric excess in the F410M NIRCam image consistent with [O III]+H$\beta$ emission at the same redshift. The spectral energy distribution of JADES-GS-z7-LA indicates a `bursty' star-formation history, with a low stellar mass of $10^{7.15}$ M$_\odot$. The only explanation of the high EW Ly$\alpha$ emission seen in JADES-GS-z7-LA is if it resides in an ionized bubble with radius $\gtrsim 3$ pMpc. Owing to the faint nature of JADES-GS-z7-LA, we show that it is incapable of single-handedly ionizing a bubble large enough. Therefore, we suggest that JADES-GS-z7-LA (and possibly the companion source) may be a part of a larger overdensity, presenting direct evidence of overlapping ionized bubbles at $z>7$, allowing us to study the process of reionization across both small and large scales.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Tobias J. Looser
Francesco D'Eugenio
Roberto Maiolino
Joris Witstok
Lester Sandles
Emma Curtis-Lake
Jacopo Chevallard
Sandro Tacchella
Benjamin D. Johnson
William M. Baker
Katherine A. Suess
Stefano Carniani
Pierre Ferruit
Santiago Arribas
Nina Bonaventura
Andrew J. Bunker
Alex J. Cameron
Stephane Charlot
Mirko Curti
Anna de Graaff
Abstract： Local galaxies are known to broadly follow a bimodal distribution: actively star forming and quiescent systems (i.e. galaxies with no or negligible star formation activity at the epoch of observation). Why, when and how such bimodality was established, and whether it has been associated with different processes at different cosmic epochs, is still a key open question in extragalactic astrophysics. Directly observing early quiescent galaxies in the primordial Universe is therefore of utmost importance to constraining models of galaxy formation and transformation. Early quiescent galaxies have been identified out to redshift $z < 5$, and these are all found to be massive ($M_{*}>10^{10}~M_{\odot}$). Here we report the discovery of a quiescent galaxy at z$=$7.3, when the Universe was only 700 Myr old - about 5% of its current age. The JWST/NIRSpec spectrum of this galaxy from our JADES programme exhibits a complete absence of nebular emission lines, while the Balmer break and Ly$\alpha$ drop are unambiguously detected. We infer that this galaxy experienced a short and intense burst of star formation followed by rapid quenching, about 10-20 Myr before the epoch of observation. Particularly interesting is that the mass of this quiescent galaxy is only $\sim$4-6$\times 10^8~M_{\odot}$. This mass range is sensitive to various feedback mechanisms that can result in temporary or permanent quiescence. Therefore this galaxy represents a unique opportunity to learn more about galaxy formation and transformation in the early Universe.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Sandro Tacchella
Daniel J. Eisenstein
Kevin Hainline
Benjamin D. Johnson
William M. Baker
Jakob M. Helton
Brant Robertson
Katherine A. Suess
Zuyi Chen
Erica Nelson
Dávid Puskás
Fengwu Sun
Stacey Alberts
Eiichi Egami
Ryan Hausen
George Rieke
Marcia Rieke
Irene Shivaei
Christina C. Williams
Christopher N. A. Willmer
Abstract： We present JWST NIRCam 9-band near-infrared imaging of the luminous $z=10.6$ galaxy GN-z11 from the JWST Advanced Deep Extragalactic Survey (JADES) of the GOODS-N field. We find a spectral energy distribution (SED) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 microns with a complete dropout in F115W. The core of GN-z11 is extremely compact in JWST imaging. We analyze the image with a two-component model, using a point source and a S\'{e}rsic profile that fits to a half-light radius of 200 pc and an index $n=0.9$. We find a low-surface brightness haze about $0.4''$ to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of GN-z11. At a spectroscopic redshift of 10.60 (Bunker et al. 2023), the comparison of the NIRCam F410M and F444W images spans the Balmer jump. From population synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the SED of GN-z11, finding a stellar mass of $\sim$$10^{9}~M_{\odot}$, a star-formation rate of $\sim$$20~M_{\odot}~\mathrm{yr}^{-1}$ and a young stellar age of $\sim$$20~\mathrm{Myr}$. As massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of GN-z11, finding 9 galaxies out to $\sim$5 comoving Mpc transverse with photometric redshifts consistent with $z=10.6$, and a 10$^{\rm th}$ more tentative dropout only $3''$ away.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Joris Witstok
Irene Shivaei
Renske Smit
Roberto Maiolino
Stefano Carniani
Emma Curtis-Lake
Pierre Ferruit
Santiago Arribas
Andrew J. Bunker
Alex J. Cameron
Stephane Charlot
Jacopo Chevallard
Mirko Curti
Anna de Graaff
Francesco D'Eugenio
Giovanna Giardino
Tobias J. Looser
Tim Rawle
Bruno Rodríguez del Pino
Chris Willott
Abstract： Interstellar dust captures a significant fraction of elements heavier than helium in the solid state and is an indispensable component both in theory and observations of galaxy evolution. Dust emission is generally the primary coolant of the interstellar medium (ISM) and facilitates the gravitational collapse and fragmentation of gas clouds from which stars form, while altering the emission spectrum of galaxies from ultraviolet (UV) to far-infrared wavelengths through the reprocessing of starlight. However, the astrophysical origin of various types of dust grains remains an open question, especially in the early Universe. Here we report direct evidence for the presence of carbonaceous grains from the detection of the broad UV absorption feature around $2175 \, \mathring{\rm A}$ in deep near-infrared spectra of galaxies up to the first billion years of cosmic time, at a redshift ($z$) of $\sim 7$. This dust attenuation feature has previously only been observed spectroscopically in older, more evolved galaxies at redshifts of $z < 3$. The carbonaceous grains giving rise to this feature are often thought to be produced on timescales of hundreds of millions of years by asymptotic giant branch (AGB) stars. Our results suggest a more rapid production scenario, likely in supernova (SN) ejecta.
Peer Review Status:Awaiting Review
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