A Remarkably Luminous Galaxy at z=11.1 Measured with Hubble Space Telescope Grism Spectroscopy (1603.00461v1)

Abstract: We present Hubble WFC3/IR slitless grism spectra of a remarkably bright $z\gtrsim10$ galaxy candidate, GN-z11, identified initially from CANDELS/GOODS-N imaging data. A significant spectroscopic continuum break is detected at $\lambda=1.47\pm0.01~\mu$m. The new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. The only viable solution is that this continuum break is the Ly$\alpha$ break redshifted to ${z_\mathrm{grism}=11.09^{+0.08}_{-0.12}}$, just $\sim$400 Myr after the Big Bang. This observation extends the current spectroscopic frontier by 150 Myr to well before the Planck (instantaneous) cosmic reionization peak at z~8.8, demonstrating that galaxy build-up was well underway early in the reionization epoch at z>10. GN-z11 is remarkably and unexpectedly luminous for a galaxy at such an early time: its UV luminosity is 3x larger than L* measured at z~6-8. The Spitzer IRAC detections up to 4.5 $\mu$m of this galaxy are consistent with a stellar mass of ${\sim10^{9}~M_\odot}$. This spectroscopic redshift measurement suggests that the James Webb Space Telescope (JWST) will be able to similarly and easily confirm such sources at z>10 and characterize their physical properties through detailed spectroscopy. Furthermore, WFIRST, with its wide-field near-IR imaging, would find large numbers of similar galaxies and contribute greatly to JWST's spectroscopy, if it is launched early enough to overlap with JWST.

• The paper spectroscopically confirms the galaxy GN-z11 at a redshift of z=11.09 using a Lyman-alpha break observed with Hubble Space Telescope grism data, pushing the spectroscopic redshift record to an earlier epoch.
• GN-z11 is remarkably luminous, three times brighter than expected for galaxies at z=6-8, suggesting efficient early galaxy formation mechanisms that challenge current theoretical models.
• Spitzer observations indicate a stellar mass of approximately 10^9 solar masses for GN-z11, providing crucial data for understanding the formation and evolution dynamics of galaxies shortly after the Big Bang.

A Spectroscopic Analysis of a Luminous High-Redshift Galaxy: Insights and Implications

The paper "A Remarkably Luminous Galaxy at z = 11.1 Measured with Hubble Space Telescope Grism Spectroscopy" presents a detailed spectroscopic investigation into an exceptionally bright galaxy, GN-z11, situated at a redshift of 11.1, utilizing Hubble Space Telescope (HST) slitless grism spectra. This research extends the observational boundary of high-redshift galaxies and provides a critical data point for understanding galaxy formation shortly after the Big Bang, approximately 400 million years subsequent to it.

Key Findings

1. Redshift Confirmation and Methodology: The research utilizes HST's WFC3/IR slitless grism data to identify a significant continuum break in GN-z11 at a wavelength of 1.47±0.01 μm. The absence of viable lower redshift solutions suggests that this feature is the Lyman-alpha break, placing the galaxy at a spectroscopic redshift of z = 11.09. This result moves the spectroscopic redshift record into an earlier epoch of cosmic history than previously achieved.
2. Implications of Luminance: GN-z11's ultraviolet luminosity is markedly higher—threefold larger—when juxtaposed with the characteristic luminosity L* at redshifts 6 to 8. This suggests efficient early galaxy formation mechanisms, challenging established models predicting fewer massive galaxies existing so soon after cosmic dawn.
3. Stellar Mass and Spectroscopic Observations: The observations from Spitzer's IRAC up to 4.5 μm provide a comprehensive characterization of the galaxy's spectral energy distribution, suggesting a stellar mass approximately 10^9 M⊙. Such findings are pivotal in understanding the formation and evolution dynamics of galaxies in the early universe.
4. Potential for Future Observations: The paper projects expectations for future instruments like the James Webb Space Telescope (JWST) and the anticipated contributions from the planned WFIRST mission. JWST is anticipated to facilitate further confirmation and characterization of high-redshift sources through detailed spectroscopy.

Practical and Theoretical Implications

• Galaxy Formation Insights:

The data offer a compelling glimpse into the state of the universe during the epoch of reionization. The discovery illustrates galaxy build-up processes during this crucial juncture, providing a reference point against which theoretical models of galaxy formation can be tested and refined.

• Constraints on Cosmic Reionization:

Detecting such a luminous galaxy at z > 10 speaks to the advanced state of galaxy formation at this redshift, offering constraints on models of cosmic reionization and the evolution of the early intergalactic medium.

• Impact on UV Luminosity Function:

The presence of such bright galaxies has implications for the shape and evolution of the UV luminosity function at extremely high redshifts. It necessitates revisiting assumptions about star formation and feedback processes during this period.

Future Considerations

The paper effectively sets the stage for subsequent observational strategies with next-generation telescopes. With the spectroscopic frontier pushed back, there is room for considerable advancements in understanding the intricacies of early galaxy evolution and cosmic conditions. Continued investigation into such distant galaxies will enhance our understanding of the universe's formative phases, potentially altering our conceptual models of galaxy distribution and growth in the nascent universe.