Finding Peas in the Early Universe with JWST Rhoads, James E.; Wold, Isak G. B.; Harish, Santosh ...
Astrophysical journal. Letters,
01/2023, Letnik:
942, Številka:
1
Journal Article
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Abstract
The Early Release Observations (EROs) of JWST beautifully demonstrate the promise of JWST in characterizing the universe at Cosmic Dawn. We analyze the Near Infrared Spectrograph ERO spectra ...of three
z
∼ 8 galaxies to determine their metallicities, gas temperatures, and ionization. These galaxies offer the first opportunity to understand the physical properties of Epoch-of-Reionization galaxies through detailed rest-optical emission-line spectroscopy. We show that these objects have metal abundances
12
+
log
O
/
H
≈
6.9–8.3, based on both the
T
e
method and on a recent calibration of the
R
23
metallicity indicator. Since the spectra are some of the earliest science data from JWST, we compare several line ratios with values expected from robust physics, to validate our measurement procedures. We compare the abundances and emission-line ratios to a nearby sample of Green Pea galaxies—a population of nearby emission-line galaxies whose UV properties resemble Epoch-of-Reionization galaxies, and which often have large Lyman continuum escape fractions. The JWST data show striking further similarities between these high-redshift galaxies and nearby Green Peas. The
z
∼ 8 galaxies span the metallicity range covered by Green Peas. They also show the compact morphology that is typical of emission-line-dominated galaxies at all redshifts. Based on these similarities with Green Peas, it is likely that these are the first rest-optical spectra of galaxies that are actively driving cosmological reionization.
Abstract
We study the dependence of Ly
α
escape from galaxies on UV continuum size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the best local analogs of high-redshift Ly
α
...emitters (LAEs). We use the Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope to measure the UV size and luminosity with 0.″047 spatial resolution. Like most galaxies the GPs show a log-normal size distribution. They also show a positive correlation between size and UV-continuum luminosity. The slope of the size-continuum luminosity relation for GPs is consistent with those of continuum-selected star-forming galaxies (SFGs) at low and high redshifts. A distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a population spread (1
σ
) of 0.19 kpc. The peak of the size distribution and the intercept of the size–luminosity relation of GPs are noticeably smaller than those of continuum-selected SFGs at similar redshifts. There are statistically significant anticorrelations found between the circularized half-light radius (
r
cir,50
), the Ly
α
equivalent width (EW(Ly
α
)), and the Ly
α
escape faction (
), suggesting that small UV-continuum radii are crucial for Ly
α
emission. GPs and high-redshift LAEs have similar sizes, once spatial resolution effects are properly considered. Our results show that a compact small size is crucial for escape of Ly
α
photons, and that Ly
α
emitters show constant characteristic size independent of their redshift.
Abstract
We present a multiwavelength analysis of the galaxy cluster SPT-CL J0607-4448 (SPT0607), which is one of the most distant clusters discovered by the South Pole Telescope at
z
= 1.4010 ± ...0.0028. The high-redshift cluster shows clear signs of being relaxed with well-regulated feedback from the active galactic nucleus (AGN) in the brightest cluster galaxy (BCG). Using Chandra X-ray data, we construct thermodynamic profiles and determine the properties of the intracluster medium. The cool-core nature of the cluster is supported by a centrally peaked density profile and low central entropy (
K
0
=
18
−
9
+
11
keV cm
2
), which we estimate assuming an isothermal temperature profile due to the limited spectral information given the distance to the cluster. Using the density profile and gas cooling time inferred from the X-ray data, we find a mass-cooling rate
M
̇
cool
=
100
−
60
+
90
M
⊙
yr
−1
. From optical spectroscopy and photometry around the O
ii
emission line, we estimate that the BCG star formation rate is
SFR
O
II
=
1.7
−
0.6
+
1.0
M
⊙
yr
−1
, roughly two orders of magnitude lower than the predicted mass-cooling rate. In addition, using ATCA radio data at 2.1 GHz, we measure a radio jet power
P
cav
=
3.2
−
1.3
+
2.1
×
10
44
erg s
−1
, which is consistent with the X-ray cooling luminosity (
L
cool
=
1.9
−
0.5
+
0.2
×
10
44
erg s
−1
within
r
cool
= 43 kpc). These findings suggest that SPT0607 is a relaxed, cool-core cluster with AGN-regulated cooling at an epoch shortly after cluster formation, implying that the balance between cooling and feedback can be reached quickly. We discuss the implications for these findings on the evolution of AGN feedback in galaxy clusters.
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.
Abstract
We present the discovery of the most distant, dynamically relaxed cool core cluster, SPT-CL J2215−3537 (SPT2215), and its central brightest cluster galaxy (BCG) at
z
= 1.16. Using new X-ray ...observations, we demonstrate that SPT2215 harbors a strong cool core with a central cooling time of 200 Myr (at 10 kpc) and a maximal intracluster medium cooling rate of 1900 ± 400
M
⊙
yr
−1
. This prodigious cooling may be responsible for fueling the extended, star-forming filaments observed in Hubble Space Telescope imaging. Based on new spectrophotometric data, we detect bright O
ii
emission in the BCG, implying an unobscured star formation rate (SFR) of
320
−
140
+
230
M
⊙
yr
−1
. The detection of a weak radio source (2.0 ± 0.8 mJy at 0.8 GHz) suggests ongoing feedback from an active galactic nucleus (AGN), though the implied jet power is less than half the cooling luminosity of the hot gas, consistent with cooling overpowering heating. The extreme cooling and SFR of SPT2215 are rare among known cool core clusters, and it is even more remarkable that we observe these at such high redshift, when most clusters are still dynamically disturbed. The high mass of this cluster, coupled with the fact that it is dynamically relaxed with a highly isolated BCG, suggests that it is an exceptionally rare system that must have formed very rapidly in the early universe. Combined with the high SFR, SPT2215 may be a high-
z
analog of the Phoenix cluster, potentially providing insight into the limits of AGN feedback and star formation in the most massive galaxies.
Abstract
The environments where galaxies reside crucially shape their star formation histories. We investigate a large sample of 1626 cluster galaxies located within 105 galaxy clusters spanning a ...large range in redshift (0.26 <
z
< 1.13). The galaxy clusters are massive (
M
500
≳ 2 × 10
14
M
⊙
) and uniformly selected from the SPT and ACT Sunyaev–Zel’dovich surveys. With spectra in hand for thousands of cluster members, we use the galaxies’ position in projected phase space as a proxy for their infall times, which provides a more robust measurement of environment than quantities such as projected clustercentric radius. We find clear evidence for a gradual age increase of the galaxy’s mean stellar populations (∼0.71 ± 0.4 Gyr based on a 4000 Å break, D
n
4000) with the time spent in the cluster environment. This environmental quenching effect is found regardless of galaxy luminosity (faint or bright) and redshift (low or high-
z
), although the exact stellar age of galaxies depends on both parameters at fixed environmental effects. Such a systematic increase of D
n
4000 with infall proxy would suggest that galaxies that were accreted into hosts earlier were quenched earlier due to longer exposure to environmental effects such as ram pressure stripping and starvation. Compared to the typical dynamical timescales of 1–3 Gyr of cluster galaxies, the relatively small age increase (∼0.71 ± 0.4 Gyr) found in our sample galaxies seems to suggest that a slow environmental process such as starvation is the dominant quenching pathway. Our results provide new insights into environmental quenching effects spanning a large range in cosmic time (∼5.2 Gyr,
z
= 0.26–1.13) and demonstrate the power of using a kinematically derived infall time proxy.
Abstract
We present the first spatially resolved maps of gas-phase metallicity for two dust-obscured star-forming galaxies at
z
∼ 4, from the JWST TEMPLATES Early Release Science program, derived ...from NIRSpec integral field unit spectroscopy of the H
α
and N
ii
emission lines. Empirical optical line calibrations are used to determine that the sources are globally enriched to near-solar levels. While one source shows elevated N
ii
/H
α
ratios and broad H
α
emission consistent with the presence of an active galactic nucleus in a ≳1 kpc region, we argue that both systems have already undergone significant metal enrichment as a result of their extremely high star formation rates. Utilizing Atacama Large Millimeter/submillimeter Array rest-frame 380
μ
m continuum and C
i
(
3
P
2
–
3
P
1
) line maps we compare the spatial variation of the metallicity and gas-to-dust ratio in the two galaxies, finding the two properties to be anticorrelated on highly resolved spatial scales, consistent with various literature studies of
z
∼ 0 galaxies. The data are indicative of the enormous potential of JWST to probe the enrichment of the interstellar medium on ∼kpc scales in extremely dust-obscured systems at
z
∼ 4 and beyond.
Abstract
We analyze spectra of a gravitationally lensed galaxy, known as the Sunburst Arc, that is leaking ionizing photons, also known as the Lyman continuum (LyC). Magnification from gravitational ...lensing permits the galaxy to be spatially resolved into one region that leaks ionizing photons and several that do not. Rest-frame UV and optical spectra from Magellan target 10 different regions along the lensed Arc, including six multiple images of the LyC leaking region and four regions that do not show LyC emission. The rest-frame optical spectra of the ionizing photon emitting regions reveal a blueshifted (Δ
V
= 27 km s
−1
) broad emission component (FWHM = 327 km s
−1
), comprising 55% of the total O
iii
line flux, in addition to a narrow component (FWHM = 112 km s
−1
), suggesting the presence of strong highly ionized gas outflows. This is consistent with the high-velocity ionized outflow inferred from the rest-frame UV spectra. In contrast, the broad emission component is less prominent in the nonleaking regions, comprising ∼26% of total O
iii
line flux. The high-ionization absorption lines are prominent in both the leaker and the nonleaker, but the low-ionization absorption lines are very weak in the leaker, suggesting that the line-of-sight gas is highly ionized in the leaker. Analyses of stellar wind features reveal that the stellar population of the LyC leaking regions is considerably younger (∼3 Myr) than that of the nonleaking regions (∼12 Myr), emphasizing that stellar feedback from young stars may play an important role in ionizing photon escape.
Abstract We present the results of our search for Lyman continuum (LyC)-emitting (weak) active galactic nuclei (AGN) at redshifts 2.3 ≲ z ≲ 4.9 from Hubble Space Telescope (HST) Wide Field Camera 3 ...(WFC3) F275W observations in the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (UVCANDELS) fields. We also include LyC emission from AGN using HST WFC3 F225W, F275W, and F336W imaging found in Early Release Science (ERS) and Hubble Deep UV Legacy Survey data. We performed exhaustive queries of the Vizier database to locate AGN with high-quality spectroscopic redshifts. In total, we found 51 AGN that met our criteria within the UVCANDELS and ERS footprints. Out of these 51, we find 12 AGN that had ≥4 σ detected LyC flux in the WFC3/UVIS images. Using a wide variety of space-based plus ground-based data, ranging from X-ray to radio wavelengths, we fit the multiwavelength photometric data of each AGN to a CIGALE spectral energy distribution (SED) using AGN models and correlate various SED parameters to the LyC flux. Kolmogorov–Smirnov tests of the SED parameter distributions for the LyC-detected and nondetected AGN showed they are likely not distinct samples. However, we find that the X-ray luminosity, star formation onset age, and disk luminosity show strong correlations relative to their emitted LyC flux. We also find strong correlations of the LyC flux to several dust parameters, i.e., polar and toroidal dust emission and 6 μ m luminosity, and anticorrelations with metallicity and A FUV . We simulate the LyC escape fraction ( f esc ) using the CIGALE and intergalactic medium transmission models for the LyC-detected AGN and find an average f esc ≃ 18%, weighted by uncertainties. We stack the LyC fluxes of subsamples of AGN according to the wavelength continuum region in which they are detected and find no significant distinctions in their LyC emission, although our submillimeter-detected F336W sample (3.15 < z < 3.71) shows the brightest stacked LyC flux. These findings indicate that LyC production and escape in AGN are more complicated than the simple assumption of thermal emission and a 100% escape fraction. Further testing of AGN models with larger samples than presented here is needed.
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