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Star Formation under a Cosmic Microscope: Highly magnified z = 11 galaxy behind the Bullet Cluster

Maruša Bradač, Jon Judež, Chris Willott, Gregor Rihtaršič, Nicholas S. Martis, Anishya Harshan, Giordano Felicioni, Yoshihisa Asada, Guillaume Desprez, Douglas Clowe, Anthony H. Gonzalez, Christine Jones, Brian C. Lemaux, Maxim Markevitch, Vladan Markov, Lamiya Mowla, Gaël Noirot, Annika H. G. Peter, Andrew Robertson, Ghassan T. E. Sarrouh, Marcin Sawicki, Tim Schrabback, Roberta Tripodi

Abstract

We present measurements of stellar population properties of a newly discovered spectroscopically confirmed $z=11.10^{+0.11}_{-0.26}$, gravitationally lensed galaxy, using JWST NIRSpec PRISM spectroscopy and NIRCam imaging. The arc is highly magnified by the Bullet Cluster (magnification factor $μ=14.0^{+6.2}_{-0.3}$. It contains three star-forming components of which one is barely resolved and two are unresolved, giving intrinsic sizes of $\lesssim 10pc$. The clumps also contain ~50% of the total stellar mass. The galaxy formed the majority of its stars ~150Myr ago (by z~14). The spectrum shows a pronounced damping wing, typical for galaxies deep in the reionisation era and indicating a neutral IGM at this line of sight. The intrinsic luminosity of the galaxy is $0.086^{+0.008}_{-0.030} L^*$ (with $L^*$ being the characteristic luminosity for this redshift), making it the lowest luminosity spectroscopically confirmed galaxy at $z>10$ discovered to date.

Star Formation under a Cosmic Microscope: Highly magnified z = 11 galaxy behind the Bullet Cluster

Abstract

We present measurements of stellar population properties of a newly discovered spectroscopically confirmed , gravitationally lensed galaxy, using JWST NIRSpec PRISM spectroscopy and NIRCam imaging. The arc is highly magnified by the Bullet Cluster (magnification factor . It contains three star-forming components of which one is barely resolved and two are unresolved, giving intrinsic sizes of . The clumps also contain ~50% of the total stellar mass. The galaxy formed the majority of its stars ~150Myr ago (by z~14). The spectrum shows a pronounced damping wing, typical for galaxies deep in the reionisation era and indicating a neutral IGM at this line of sight. The intrinsic luminosity of the galaxy is (with being the characteristic luminosity for this redshift), making it the lowest luminosity spectroscopically confirmed galaxy at discovered to date.

Paper Structure

This paper contains 9 sections, 6 figures.

Table of Contents

  1. Introduction
  2. Data
  3. Data Analysis
  4. Spectroscopy
  5. Photometry
  6. Gravitational lens model
  7. Results
  8. Conclusions
  9. Photometry and SED fitting

Figures (6)

  • Figure 1: Top: Image of the BulletArc-z11. Shown are different filters and an RGB image (B=F090W+F115W+F150W, G=F200W+F277W+F356W, and R=F356W+F410M+F444W). The white ticks mark the central position of the source (given by R.A., Decl. in Table \ref{['tab:prop']}). The galaxy consists of two unresolved (1,3) and one barely resolved clump (3) and an underlying smooth component (labelled G). The sizes of cutouts are $1\farcs 6 \times 1\farcs6$. The point source near the center in the F115W filter is the contaminant globular cluster in the Bullet Cluster. Bottom: NIRSpec prism spectrum of BulletArc-z11. In the top panel, we show the 2D spectrum, while the bottom panel shows the 1D optimal extraction, as well as a cutout showing placement within the MSA shutters. The wavelengths of commonly observed emission lines are marked; however, none are detected with $S/N>3$. The model spectrum (red line) includes a fully neutral IGM, a neutral hydrogen damping wing column and a foreground contaminant source modeled as a globular cluster at the Bullet cluster redshift (blue dashed line).
  • Figure 2: $M_{\rm UV}$ vs redshift plot for the BulletArc-z11 (star) and spectroscopically confirmed sources from the literature (circles, collated in robertsborsani25). Fill colours represent magnification $\mu$ given by the colorbar. Open circles are blank-field sources with $\mu=1$. $M_{\rm UV}$ values for different characteristic luminosities $L^*$ (at $z\sim 10$, taken from willott24) are shown as dashed horizontal lines. The uncertainty on $M_{\rm UV}$ for BulletArc-z11 is partly hidden behind the symbol and includes lensing uncertainties.
  • Figure 3: Source plane modelling using Lenstructionyang20. From the top left, we plot the observed image (in F200W), the source model, the best fit image model (after lensing and PSF convolution have been applied), and normalised residuals. The source was modelled using an underlying galaxy component G and 3 small clumps (#1-3) modelled using Gaussian profiles.
  • Figure 4: RGB (F277W, F357W, F444W) image of the Bullet Cluster. Overlaid (in red) is the critical curve calculated at the redshift of the BulletArc-z11 used in this paper. In the inset ($10\arcsec \times 10 \arcsec$) we use high-resolution RGB images (F115W, F150W, F200W) to show the BulletArc-z11 and the same red critical curve as well as in cyan the one with a cluster member added as described in Sect. \ref{['sec:lm']}.
  • Figure 5: Results of the SED fitting using original full photometry using Photutils corrected by dividing by $\mu$ (labelled All, see also Table \ref{['tab:phot']}), and derived using Galfit for the smooth light component (G) and the three clumps (labelled C1-3). Shown are fluxes in red and SED predicted fluxes in open circles in units of $\mu\hbox{Jy}$. Derived stellar properties are given in the inset. While fluxes in F150W and shortward are shown, they were not included in the fit as the redshift is only allowed to vary based on spectroscopic redshift measurement.
  • ...and 1 more figures