Abstract
Extreme, young stellar populations are considered to be the primary contributor to cosmic reionization. How the Lyman continuum (LyC) escapes these galaxies remains highly elusive, and it is ...challenging to observe this process in actual LyC emitters without resolving the relevant physical scales. We investigate the Sunburst Arc, a strongly lensed LyC emitter at
z
= 2.37 that reveals an exceptionally small-scale (tens of parsecs) region of high LyC escape. The small (<100 pc) LyC-leaking region has extreme properties: a very blue UV slope (
β
= −2.9 ± 0.1), a high ionization state (O
iii
λ
5007/O
ii
λ
3727 = 11 ± 3 and O
iii
λ
5007/H
β
= 6.8 ± 0.4), strong oxygen emission (EW(O
iii
) = 1095 ± 40 Å), and a high Ly
α
escape fraction (0.3 ± 0.03), none of which are found in nonleaking regions of the galaxy. The leaking region’s UV slope is consistent with approximately “pure” stellar light that is minimally contaminated by the surrounding nebular continuum emission or extinguished by dust. These results suggest a highly anisotropic LyC escape process such that LyC is produced and escapes from a small, extreme starburst region where the stellar feedback from an ionizing star cluster creates one or more “pencil-beam” channels in the surrounding gas through which LyC can directly escape. Such anisotropic escape processes imply that random sight-line effects drive the significant scatters between measurements of galaxy properties and LyC escape fraction, and that strong lensing is a critical tool for resolving the processes that regulate the ionizing budget of galaxies for reionization.
Abstract
We present six strongly gravitationally lensed Ly
α
emitters (LAEs) at
z
∼ 4–5 with Hubble Space Telescope (HST) narrowband imaging isolating Ly
α
. Through complex radiative transfer Ly
α
...encodes information about the spatial distribution and kinematics of the neutral hydrogen upon which it scatters. We investigate the galaxy properties and Ly
α
morphologies of our sample. Many previous studies of high-redshift LAEs have been limited in Ly
α
spatial resolution. In this work we take advantage of high-resolution Ly
α
imaging boosted by lensing magnification, allowing us to probe subgalactic scales that are otherwise inaccessible at these redshifts. We use broadband imaging from HST (rest-frame UV) and Spitzer (rest-frame optical) in spectral energy distribution fitting, providing estimates of the stellar masses (∼10
8
–10
9
M
⊙
), stellar population ages (
t
50
< 40 Myr), and amounts of dust (
A
V
∼ 0.1–0.6, statistically consistent with zero). We employ nonparametric star formation histories to probe the young stellar populations which create the Ly
α
. We also examine the offsets between the Ly
α
and stellar continuum, finding small upper limits of offsets (<0.″1) consistent with studies of low-redshift LAEs, indicating our galaxies are not interacting or merging. Finally, we find a bimodality in our sample’s Ly
α
morphologies: clumpy and extended. We find a suggestive trend: our LAEs with clumpy Ly
α
are generally younger than the LAEs with extended Ly
α
, suggesting a possible correlation with age.
I present six strongly gravitationally lensed Lyα Emitters (LAEs) at z ∼ 4−5 with HST narrowband imaging isolating Lyα. Through complex radiative transfer, Lyα encodes information about the spatial ...distribution and kinematics of the neutral hydrogen upon which it scatters. This information can help explain how star-forming galaxies contributed to Reionization. The primary goal of this work is to investigate the galaxy properties and Lyα morphologies of this sample. Many previous studies of high-redshift LAEs have been limited in Lyα spatial resolution. In this work I take advantage of high-resolution Lyα imaging boosted by lensing magnification, allowing for probing of sub-galactic scales that are otherwise inaccessible at these redshifts. I use broadband imaging from HST (rest-frame UV) and Spitzer (rest-frame optical) in SED fitting; providing estimates on the stellar masses (∼ 108 − 109M⊙), stellar population ages (t50 < 40 Myr), and amounts of dust (AV ∼ 0.1 − 0.6, statistically consistent with zero). I employ non-parametric star-formation histories to probe the young stellar-populations which create Lyα. I also examine the offsets between the Lyα and stellar continuum, finding small upper limits of offsets (< 0.′′1) consistent with studies of low-redshift LAEs, indicating our galaxies are not interacting or merging. I find a bimodality in the sample’s Lyα morphologies: clumpy and extended. Comparing these morphologies to the inferred galaxy properties, I find a suggestive trend: our LAEs with clumpy Lyα are generally younger than the LAEs with extended Lyα, suggesting a possible correlation with age. Finally, I present preliminary results from new, state of the art forward modeling code for one object in the sample. I find that intrinsic clump sizes between Lyα and the stellar continuum are statistically equivalent, possibly indicating the presence of ionized channels in the ISM.
Abstract
We present a strong-lensing analysis of the cluster PSZ1 G311.65−18.48, based on Hubble Space Telescope imaging, archival VLT/MUSE spectroscopy, and Chandra X-ray data. This cool-core ...cluster (
z
= 0.443) lenses the brightest lensed galaxy known, dubbed the “Sunburst Arc” (
z
= 2.3703), a Lyman continuum (LyC) emitting galaxy multiply imaged 12 times. We identify in this field 14 additional strongly lensed galaxies to constrain a strong-lens model and report secure spectroscopic redshifts of four of them. We measure a projected cluster core mass of
M
(<250 kpc) =
2.93
−
0.02
+
0.01
×
10
14
M
⊙
. The two least magnified but complete images of the Sunburst Arc’s source galaxy are magnified by ∼13×, while the LyC clump is magnified by ∼4–80×. We present time delay predictions and conclusive evidence that a discrepant clump in the Sunburst Arc, previously claimed to be a transient, is not variable, thus strengthening the hypothesis that it results from an exceptionally high magnification. A source plane reconstruction and analysis of the Sunburst Arc finds its physical size to be 1 × 2 kpc and that it is resolved in three distinct directions in the source plane, 0°, 40°, and 75° (east of north). We place an upper limit of
r
≲ 50 pc on the source plane size of unresolved clumps and
r
≲ 32 pc for the LyC clump. Finally, we report that the Sunburst Arc is likely in a system of two or more galaxies separated by ≲6 kpc in projection. Their interaction may drive star formation and could play a role in the mechanism responsible for the leaking LyC radiation.
We present six strongly gravitationally lensed Ly-$\alpha$ Emitters (LAEs) at
$z\sim4-5$ with HST narrowband imaging isolating Ly-$\alpha$. Through complex
radiative transfer Ly-$\alpha$ encodes ...information about the spatial
distribution and kinematics of the neutral hydrogen upon which it scatters. We
investigate the galaxy properties and Ly-$\alpha$ morphologies of our sample.
Many previous studies of high-redshift LAEs have been limited in Ly-$\alpha$
spatial resolution. In this work we take advantage of high-resolution
Ly-$\alpha$ imaging boosted by lensing magnification, allowing us to probe
sub-galactic scales that are otherwise inaccessible at these redshifts. We use
broadband imaging from HST (rest-frame UV) and Spitzer (rest-frame optical) in
SED fitting; providing estimates on the stellar masses ($\sim 10^8 - 10^9
M_{\odot}$), stellar population ages ($t_{50} <40$ Myr), and amounts of dust
($A_V \sim 0.1 - 0.6$, statistically consistent with zero). We employ
non-parametric star-formation histories to probe the young stellar-populations
which create Ly-$\alpha$. We also examine the offsets between the Ly-$\alpha$
and stellar continuum, finding small upper limits of offsets ($< 0.1"$)
consistent with studies of low-redshift LAEs; indicating our galaxies are not
interacting or merging. Finally, we find a bimodality in our sample's
Ly-$\alpha$ morphologies: clumpy and extended. We find a suggestive trend: our
LAEs with clumpy Ly-$\alpha$ are generally younger than the LAEs with extended
Ly-$\alpha$, suggesting a possible correlation with age.
Extreme, young stellar populations are considered the primary contributor to cosmic re-ionization. How Lyman-continuum (LyC) escapes these galaxies remains highly elusive, and it is challenging to ...observe this process in actual LyC emitters without resolving the relevant physical scales. We investigate the Sunburst Arc: a strongly lensed, LyC emitter at \(z =2.37\) that reveals an exceptionally small scale (tens of parsecs) region of high LyC escape. The small (\(<\) 100 pc) LyC leaking region has extreme properties: a very blue UV slope (\(\beta = -2.9 \pm 0.1\)), high ionization state (O III\(\lambda 5007\)/O II\(\lambda 3727 \) \(= 11 \pm 3\) and O III\(\lambda 5007\)/H\(\beta\) \(=6.8 \pm 0.4\)), strong oxygen emission (EW(O III) \(= 1095 \pm 40 \ Å\)), and high Lyman-\(\alpha\) escape fraction (\(0.3 \pm 0.03\)), none of which are found in non-leaking regions of the galaxy. The leaking region's UV slope is consistent with approximately ``pure'' stellar light that is minimally contaminated by surrounding nebular continuum emission or extinguished by dust. These results suggest a highly anisotropic LyC escape process such that LyC is produced and escapes from a small, extreme starburst region where the stellar feedback from an ionizing star cluster creates one or more ``pencil beam'' channels in the surrounding gas through which LyC can directly escape. Such anisotropic escape processes imply that random sightline effects drive the significant scatters between measurements of galaxy properties and LyC escape fraction, and that strong lensing is a critical tool for resolving the processes that regulate the ionizing budget of galaxies for re-ionization.
