arXiv subjects

Tucker Jones

Publications and source records attributed to Tucker Jones.

At least 55 records · Page 3Linked to original sources

arXiv2025

The AURORA Survey: An Extraordinarily Mature, Star-forming Galaxy at $z\sim 7$

We present the properties of a massive, large, dusty, metal-rich, star-forming galaxy at z_spec=6.73. GOODSN-100182 was observed with JWST/NIRSpec as part of the AURORA survey, and is also covered by public multi-wavelength HST and JWST imaging. While the large stellar mass of GOODSN-100182 (~10^10 M_sun) was indicated prior to JWST, NIRCam rest-optical imaging now reveals the presence of an extended disk (r_eff~1.5 kpc). In addition, the NIRSpec R~1000 spectrum of GOODSN-100182 includes the detection of a large suite of rest-optical nebular emission lines ranging in wavelength from [OII]3727 up to [NII]6583. The ratios of Balmer lines suggest significant dust attenuation (E(B-V)_gas=0.40+0.10/-0.09), consistent with the red rest-UV slope inferred for GOODSN-100182 (beta=-0.50+/-0.09). The star-formation rate based on dust-corrected H-alpha emission is log(SFR(H-alpha)/ M_sun/yr)=2.02+0.13/-0.14, well above the z~7 star-forming main sequence in terms of specific SFR. Strikingly, the ratio of [NII]6583/H-alpha emission suggests almost solar metallicity, as does the ratio ([OIII]5007/H-beta)/([NII]6583/H-alpha) and the detection of the faint [FeII]4360 emission feature. Overall, the excitation and ionization properties of GOODSN-100182 more closely resemble those of typical star-forming galaxies at z~2-3 rather than z~7. Based on public spectroscopy of the GOODS-N field, we find that GOODSN-100182 resides within a significant galaxy overdensity, and is accompanied by a spectroscopically-confirmed neighbor galaxy. GOODSN-100182 demonstrates the existence of mature, chemically-enriched galaxies within the first billion years of cosmic time, whose properties must be explained by galaxy formation models.

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arXiv2025

Spatially Resolved Galactic Winds at Cosmic Noon: Outflow Kinematics and Mass Loading in a Lensed Star-Forming Galaxy at $z=1.87$

We study the spatially resolved outflow properties of CSWA13, an intermediate mass ($M_*=10^{9}~\mathrm{M}_{\odot}$), gravitationally lensed star-forming galaxy at $z=1.87$. We use Keck/KCWI to map outflows in multiple rest-frame ultraviolet ISM absorption lines, along with fluorescent Si II$^*$ emission, and nebular emission from C III] tracing the local systemic velocity. The spatial structure of outflow velocity mirrors that of the nebular kinematics, which we interpret to be a signature of a young galactic wind that is pressurizing the ISM of the galaxy but is yet to burst out. From the radial extent of Si II$^*$ emission, we estimate that the outflow is largely encapsulated within $3.5$ kpc. We explore the geometry (e.g., patchiness) of the outflow by measuring the covering fraction at different velocities, finding that the maximum covering fraction is at velocities $v\simeq-150$ km$\,$s$^{-1}$. Using the outflow velocity ($v_{out}$), radius ($R$), column density ($N$), and solid angle ($Ω$) based on the covering fraction, we measure the mass loss rate $\log\dot{m}_{out}/(\mathrm{M}_{\odot}\text{yr}^{-1}) = 1.73\pm0.23$ and mass loading factor $\logη= 0.04\pm0.34$ for the low-ionization outflowing gas in this galaxy. These values are relatively large and the bulk of the outflowing gas is moving with speeds less than the escape velocity of the galaxy halo, suggesting that the majority of outflowing mass will remain in the circumgalactic medium and/or recycle back into the galaxy. The results support a picture of high outflow rates transporting mass and metals into the inner circumgalactic medium, providing the gas reservoir for future star formation.

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arXiv2025

The AURORA Survey: A New Era of Emission-line Diagrams with JWST/NIRSpec

We present results on the emission-line properties of z=1.4-7.5 star-forming galaxies in the Assembly of Ultradeep Rest-optical Observations Revealing Astrophysics (AURORA) Cycle 1 JWST/NIRSpec program. Based on its depth, continuous wavelength coverage from 1--5 microns, and medium spectral resolution (R~1000), AURORA includes detections of a large suite of nebular emission lines spanning a broad range in rest wavelength. We investigate the locations of AURORA galaxies in multiple different emission-line diagrams, including traditional "BPT" diagrams of [OIII]/Hbeta vs. [NII]/Halpha, [SII]/Halpha, and [OI]/Halpha, and the "ionization-metallicity" diagram of [OIII]/[OII] (O32) vs. ([OIII]+[OII])/Hbeta (R23). We also consider a bluer rest-frame "ionization-metallicity" diagram introduced recently to characterize z>10 galaxies: [NeIII]/[OII] vs. ([NeIII]+[OII])/Hdelta; as well as longer-wavelength diagnostic diagrams extending into the rest-frame near-IR: [OIII]/Hbeta vs. [SIII]/[SII] (S32); and HeI/Pagamma and [SIII]/Pagamma vs. [FeII]/Pabeta. With a significant boost in signal-to-noise and large, representative samples of individual galaxy detections, the AURORA emission-line diagrams presented here definitively confirm a physical picture in which chemically-young, alpha-enhanced, massive stars photoionize the ISM in distant galaxies with a harder ionizing spectrum at fixed nebular metallicity than in their z~0 counterparts. We also uncover previously unseen evolution prior to z~2 in the [OIII]/Hbeta vs. [NII]/Halpha diagram, which motivates deep NIRSpec observations at even higher redshift. Finally, we present the first statistical sample of rest-frame near-IR emission-line diagnostics in star-forming galaxies at high redshift. In order to truly interpret rest-frame near-IR line ratios including [FeII], we must obtain better constraints on dust depletion in the high-redshift ISM.

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arXiv2024

MSA-3D: Metallicity Gradients in Galaxies at $z\sim1$ with JWST/NIRSpec Slit-stepping Spectroscopy

The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at $0.5 \lesssim z \lesssim 1.7$ from the \msasd survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST's diffraction limit and a high spectral resolution of $R\simeq2700$. The metallicity gradients measured in our galaxy sample range from $-$0.03 to 0.02 dex~kpc$^{-1}$. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at $z\sim1$ with small intrinsic scatter of 0.02 dex~kpc$^{-1}$. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more ``disky". This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of JWST NIRSpec/MSA in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution.

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arXiv2024

Early Results from GLASS-JWST. XXV. Electron Density in the Interstellar Medium at $0.7\lesssim z\lesssim 9.3$ with NIRSpec High-resolution Spectroscopy

The electron density (${n_{\rm e}}$) of the interstellar medium (ISM) in star-forming galaxies is intimately linked to star formation and ionization condition. Using the high-resolution spectra obtained from the JWST NIRSpec micro shutter assembly (MSA) as part of the GLASS-JWST program, we have assembled the largest sample to date (34 galaxies) with individual ${n_{\rm e}}$ measurements derived from the [OII] $λλ$3726,29 and/or [SII] $λλ$6718,32 doublets at $0.7\lesssim z\lesssim 9.3$. The gravitational lensing magnification by the foreground Abell~2744 cluster allows us to probe ${n_{\rm e}}$ in galaxies with stellar masses ($M_{*}$) down to $\simeq 10^{7.5} M_\odot$ across the entire redshift range. Our analysis reveals that the [OII] flux ratios are marginally anti-correlated with specific star formation rate (sSFR) within a 1-$σ$ confidence interval, whereas the [SII] flux ratios show no significant correlation with sSFR. Despite clear correlation between sSFR and redshift within our sample, we find no apparent redshift evolution of ${n_{\rm e}}$ at $z \simeq 1-9$. Our dataset also includes 13 galaxies where ${n_{\rm e}}$ can be measured from both [OII] and [SII]. Contrary to findings at lower redshifts, we observe considerable scatter in ${n_{\rm e}}$ measurements from [OII] and [SII], indicating a complex gaseous environment with significant variations in ${n_{\rm e}}$ in high-redshift galaxies. This work highlights the unique capability of JWST NIRSpec/MSA high-resolution spectroscopy to characterize the detailed physical properties of the ISM in individual high-redshift galaxies.

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arXiv2024

BEACON: JWST NIRCam Pure-parallel Imaging Survey. I. Survey Design and Initial Results

We introduce the Bias-free Extragalactic Analysis for Cosmic Origins with NIRCam (BEACON) survey, a JWST Cycle2 program allocated up to 600 pure-parallel hours of observations. BEACON explores high-latitude areas of the sky with JWST/NIRCam over $\sim100$ independent sightlines, totaling $\sim0.3$deg$^2$, reaching a median F444W depth of $\approx28.2$AB mag (5$σ$). Based on existing JWST observations in legacy fields, we estimate that BEACON will photometrically identify 25--150 galaxies at $z>10$ and 500--1000 at $z\sim7$--10 uniquely enabled by an efficient multiple filter configuration spanning $0.9$--5.0$μ$m. The expected sample size of $z>10$ galaxies will allow us to obtain robust number density estimates and to discriminate between different models of early star formation. In this paper, we present an overview of the survey design and initial results using the first 19 fields. We present 129 galaxy candidates at $z>7$ identified in those fields, including 11 galaxies at $z>10$ and several UV-luminous ($M_{\rm UV}<-21$mag) galaxies at $z\sim8$. The number densities of $z<13$ galaxies inferred from the initial fields are overall consistent with those in the literature. Despite reaching a considerably large volume ($\sim10^5$Mpc$^3$), however, we find no galaxy candidates at $z>13$, providing us with a complimentary insight into early galaxy evolution with minimal cosmic variance. We publish imaging and catalog data products for these initial fields. Upon survey completion, all BEACON data will be coherently processed and distributed to the community along with catalogs for redshift and other physical quantities.

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arXiv2024

Detection of gas inflow during the onset of a starburst in a low-mass galaxy at z=2.45

The baryon cycle is crucial for understanding galaxy formation, as gas inflows and outflows vary throughout a galaxy's lifetime and affect its star formation rate. Despite the necessity of accretion for galaxy growth at high redshifts, direct observations of inflowing gas have proven elusive especially at $z\gtrsim2$. We present spectroscopic analysis of a galaxy at redshift $z=2.45$ which exhibits signs of inflow in several ultraviolet interstellar absorption lines, with no clear outflow signatures. The absorption lines are redshifted by $\sim$250 km sec$^{-1}$ with respect to the systemic redshift, and C IV shows a prominent inverse P-Cygni profile. Simple stellar population models suggest that this galaxy has a low metallicity ($\sim$5% solar), with a very young starburst of age $\sim$4 Myr dominating the ultraviolet luminosity. The gas inflow velocity and nebular velocity dispersion suggest an approximate halo mass of order $\sim 10^{11}M_{\odot}$, a regime in which simulations predict that bursty star formation is common at this redshift. We conclude that this system is likely in the beginning of a cycle of bursty star formation, where inflow and star formation rates are high, but where supernovae and other feedback processes have not yet launched strong outflows. In this scenario, we expect the inflow-dominated phase to be observable (e.g., with net redshifted ISM absorption) for only a short timescale after a starburst onset. This result represents a promising avenue for probing the full baryon cycle, including inflows, during the formative phases of low-mass galaxies at high redshifts.

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arXiv2024

MSA-3D: dissecting galaxies at z~1 with high spatial and spectral resolution

Integral field spectroscopy (IFS) is a powerful tool for understanding the formation of galaxies across cosmic history. We present the observing strategy and first results of MSA-3D, a novel JWST program using multi-object spectroscopy in a slit-stepping strategy to produce IFS data cubes. The program observed 43 normal star-forming galaxies at redshifts $0.5 \lesssim z \lesssim 1.5$, corresponding to the epoch when spiral thin-disk galaxies of the modern Hubble sequence are thought to emerge, obtaining kpc-scale maps of rest-frame optical nebular emission lines with spectral resolution $R\simeq2700$. Here we describe the multiplexed slit-stepping method which is $>15$ times more efficient than the NIRSpec IFS mode for our program. As an example of the data quality, we present a case study of an individual galaxy at $z=1.104$ (stellar mass $M_{*} = 10^{10.3}~M_{\odot}$, star formation rate~$=3~M_{\odot}$ yr$^{-1}$) with prominent face-on spiral structure. We show that the galaxy exhibits a rotationally supported disk with moderate velocity dispersion ($σ= 36^{+5}_{-4}$~\kms), a negative radial metallicity gradient ($-0.020\pm0.002$~dex\,kpc$^{-1}$), a dust attenuation gradient, and an exponential star formation rate density profile which closely matches the stellar continuum. These properties are characteristic of local spirals, indicating that mature galaxies are in place at $z\sim1$. We also describe the customized data reduction and original cube-building software pipelines which we have developed to exploit the powerful slit-stepping technique. Our results demonstrate the ability of JWST slit-stepping to study galaxy populations at intermediate to high redshifts, with data quality similar to current surveys of the $z\sim0.1$ universe.

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arXiv2024

Liger at W.M. Keck Observatory: imager structural analysis, fabrication, and characterization plan

Liger is an adaptive optics (AO) fed imager and integral field spectrograph (IFS) designed to take advantage of the Keck All-sky Precision Adaptive-optics (KAPA) upgrade to the Keck I telescope. Liger adapts the design of the InfraRed Imaging Spectrograph (IRIS) for the Thirty Meter Telescope (TMT) to Keck by implementing a new imager and re-imaging optics. The performance of the imager is critical as it sequentially feeds the spectrograph and contains essential components such as the pupil wheel, filter wheel, and pupil viewing camera. We present the design and structural analysis of the Liger imager optical assembly including static, modal, and thermal simulations. We present the fabrication as well as the full assembly and characterization plan. The imager will be assembled bench-top in a clean room utilizing a coordinate-measuring machine (CMM) for warm alignment. To ensure optimal performance, the imager will be characterized in a test cryostat before integration with the full Liger instrument. This comprehensive approach to characterization ensures the precision and reliability of the imager, enhancing the observational capabilities of Liger and W.M. Keck Observatory.

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arXiv2024

The Carousel Lens: A Well-Modeled Strong Lens with Multiple Lensed Sources

Over the past few years alone, the lensing community has discovered thousands of strong lens candidates, and spectroscopically confirmed hundreds of them. In this time of abundance, it becomes pragmatic to focus our time and resources on the few extraordinary systems, in order to most efficiently study the universe. In this paper, we present such a system: DESI-090.9854-35.9683, a cluster-scale lens at $z_{\rm l} = 0.49$, with seven observed lensed sources around the core, and additional lensed sources further out in the cluster. From the number and the textbook configuration of the lensed images, a tight constraint on the mass potential of the lens is possible. This would allow for detailed analysis on the dark and luminous matter content within galaxy clusters, as well as a probe into dark energy and high-redshift galaxies. We present our spatially resolved kinematic measurements of this system from the Very Large Telescope Multi Unit Spectroscopic Explorer, which confirm five of these source galaxies (in ascending order, at $z_{\rm s} = 0.962, 0.962, 1.166, 1.432,$ and $1.432$). With previous Hubble Space Telescope imaging in the F140W and F200LP bands, we also present a simple two power-law profile flux-based lens model that, for a cluster lens, well models the five lensed arc families with redshifts. We determine the mass to be $M(< θ_{\rm E}) = 4.78\times10^{13} M_{\odot}$ for the primary mass potential. From the model, we extrapolate the redshift of one of the two source galaxies not yet spectroscopically confirmed to be at $z_{\rm s}=4.52^{+1.03}_{-0.71}$.

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arXiv2024

Gravitational Lensing Reveals Cool Gas within 10-20 kpc around a Quiescent Galaxy

While quiescent galaxies have comparable amounts of cool gas in their outer circumgalactic medium (CGM) compared to star-forming galaxies, they have significantly less interstellar gas. However, open questions remain on the processes causing galaxies to stop forming stars and stay quiescent . Theories suggest dynamical interactions with the hot corona prevent cool gas from reaching the galaxy, therefore predicting the inner regions of quiescent galaxy CGMs are devoid of cool gas. However, there is a lack of understanding of the inner regions of CGMs due to the lack of spatial information in quasar-sightline methods. We present integral-field spectroscopy probing 10--20~kpc (2.4--4.8 R\textsubscript{e}) around a massive quiescent galaxy using a gravitationally lensed star-forming galaxy. We detect absorption from Magnesium (MgII) implying large amounts of cool atomic gas (10\textsuperscript{8.4} -- 10\textsuperscript{9.3} M\textsubscript{$\odot$} with T$\sim$10\textsuperscript{4} Kelvin), in comparable amounts to star-forming galaxies. Lens modeling of Hubble imaging also reveals a diffuse asymmetric component of significant mass consistent with the spatial extent of the MgII absorption, and offset from the galaxy light profile. This study demonstrates the power of galaxy-scale gravitational lenses to not only probe the gas around galaxies, but to also independently probe the mass of the CGM due to it's gravitational effect.

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arXiv2024

AGEL: Is the Conflict Real? Investigating Galaxy Evolution Models using Strong Lensing at 0.3 < z < 0.9

Observed evolution of the total mass distribution with redshift is crucial to testing galaxy evolution theories. To measure the total mass distribution, strong gravitational lenses complement the resolved dynamical observations currently limited to $z \lesssim 0.5$. Here we present the lens models for a pilot sample of seven galaxy-scale lenses from the ASTRO3D Galaxy Evolution with Lenses (AGEL) survey. The AGEL lenses, modeled using HST/WFC3-F140W images with Gravitational Lens Efficient Explorer (GLEE) software, have deflector redshifts between $0.3 < z_{\rm defl} < 0.9$. Assuming a power-law density profile with slope $γ$, we measure the total density profile for the deflector galaxies via lens modeling. We also measure the stellar velocity dispersions ($σ_{\rm obs}$) for four lenses and obtain $σ_{\rm obs}$ from SDSS-BOSS for the remaining lenses to test our lens models by comparing observed and model-predicted velocity dispersions. For the seven AGEL lenses, we measure an average density profile slope of $-1.95 \pm 0.09$ and a $γ$--$z$ relation that does not evolve with redshift at $z<1$. Although our result is consistent with some observations and simulations, it differs from other studies at $z<1$ that suggest the $γ$--$z$ relation evolves with redshift. The apparent conflicts among observations and simulations may be due to a combination of 1) systematics in the lensing and dynamical modeling; 2) challenges in comparing observations with simulations; and 3) assuming a simple power-law for the total mass distribution. By providing more lenses at $z_{\rm defl} > 0.5$, the AGEL survey will provide stronger constraints on whether the mass profiles evolve with redshift as predicted by current theoretical models.

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arXiv2024

A strong He II $λ$1640 emitter with extremely blue UV spectral slope at $z=8.16$: presence of Pop III stars?

Cosmic hydrogen reionization and cosmic production of first metals are major phase transitions of the universe occurring during the first billion years after the Big Bang, however these are still underexplored observationally. Using the JWST NIRSpec prism spectroscopy, we report the discovery of a sub-$L_\ast$ galaxy at $z_{\rm spec}=8.1623\pm0.0007$, dubbed RXJ2129-z8HeII, via the detection of a series of strong rest-frame UV/optical nebular emission lines and the clear Lyman break. RXJ2129-z8HeII shows a pronounced UV continuum with an extremely steep (i.e. blue) spectral slope of $β=-2.53_{-0.07}^{+0.06}$, the steepest amongst all spectroscopically confirmed galaxies at $z_{\rm spec}\gtrsim7$, in support of its very hard ionizing spectrum that could lead to a significant leakage of its ionizing flux. Therefore, RXJ2129-z8HeII is representative of the key galaxy population driving the cosmic reionization. More importantly, we detect a strong He II $λ$1640 emission line in its spectrum, one of the highest redshifts at which such a line is robustly detected. Its high rest-frame equivalent width (${\rm EW}=21\pm4$ Angstrom) and extreme flux ratios with respect to UV metal and Balmer lines raise the possibility that part of RXJ2129-z8HeII's stellar populations could be Pop III-like. Through careful photoionization modeling, we show that the physically calibrated phenomenological models of the ionizing spectra of Pop III stars with strong mass loss can successfully reproduce the emission line flux ratios observed in RXJ2129-z8HeII. Assuming the Eddington limit, the total mass of the Pop III stars within this system is estimated to be $7.8\pm1.4\times10^5 M_\odot$. To date, this galaxy presents the most compelling case in the early universe where trace Pop III stars might coexist with metal-enriched populations.

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arXiv2024

Studying [CII] Emission in Low-mass Galaxies at z ~ 7

We report on a $\rm{[CII]}_{158μ\rm{m}}$ search using the Atacama Large Millimeter/submillimeter Array (ALMA) on three lensed, confirmed {\lya} emitting galaxies at $z \sim 7$. Our targets are ultra-violet (UV) faint systems with stellar masses on the order of $M_{*} \sim 10^{9} M_{\odot}$. We detect a single [CII] line emission ($4σ$) from the brightest ($L \sim 2.4 \times 10^{10}L_{\odot}$) galaxy in our sample, MACS0454-1251. We determine a systemic redshift ($z_{\rm{[CII]}} = 6.3151 \pm 0.0005$) for MACS0454-1251 and measure a {\lya} velocity offset of $Δv \approx 300 \pm 70 \rm{km\,s}^{-1}$. The remaining two galaxies we detect no {\ct} but provide $3 σ$ upper limits on their {\ct} line luminosities which we use to investigate the $L_{\textrm{[CII]}} - \rm{SFR}$ relation. Overall our single {\ct} detection shows agreement with the relation for dwarf and local starburst galaxies. Our [CII] deficient galaxies could potentially be exhibiting low metallicities ($Z<Z_{\odot}$). Another possible explanation for weaker [CII] emission could be strong feedback from star formation disrupting molecular clouds. We do not detect continuum emission in any of the sources, placing upper limits on their dust masses. Assuming a single dust temperature of $T_{d}=35 \rm{K}$ dust masses ($M_{\rm{dust}}$) range from $< 4.8 \times 10^{7} M_{\odot} $ to $2.3 \times 10^{8} M_{\odot}$. Collectively, our results suggest faint reionization era sources could be metal poor and/or could have strong feedback suppressing [CII] emission.

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arXiv2024

A massive interacting galaxy 510 million years after the Big Bang

JWST observations confirm the existence of galaxies as early as 300Myr and at a higher number density than expected based on galaxy formation models and HST observations. Yet, sources confirmed spectroscopically in the first 500Myr have estimated stellar masses $<5\times10^8M_\odot$, limiting the signal to noise ratio (SNR) for investigating substructure. We present a high-resolution spectroscopic and spatially resolved study of a rare bright galaxy at $z=9.3127\pm0.0002$ with a stellar mass of $(2.5^{+0.7}_{-0.5})\times10^9M_\odot$, forming $25^{+3}_{-4}M_\odot/yr$ and with a metallicity of $\sim0.1Z_\odot$- lower than in the local universe for the stellar mass but in line with expectations of chemical enrichment in galaxies 1-2Gyr after the Big Bang. The system has a morphology typically associated to two interacting galaxies, with a two-component main clump of very young stars (age$<10$Myr) surrounded by an extended stellar population ($130\pm20$Myr old, identified by modeling the NIRSpec spectrum) and an elongated clumpy tidal tail. The spectroscopic observations identify O, Ne and H emission lines, and the Lyman break, where there is evidence of substantial Ly$α$ absorption. The [OII] doublet is resolved spectrally, enabling an estimate of the electron number density and ionization parameter of the interstellar medium and showing higher densities and ionization than in lower redshift analogs. For the first time at $z>8$, we identify evidence of absorption lines (Si, C and Fe), with low confidence individual detections but SNR$>6$ when stacked. The absorption features suggest that Ly$α$ is damped by the interstellar and circumgalactic medium. Our observations provide evidence of rapid efficient build-up of mass and metals in the immediate aftermath of the Big Bang through mergers, demonstrating that massive galaxies with several billion stars exist earlier than expected.

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arXiv2024

Reply to: Effects of density and temperature variations on the metallicity of Mrk 71

In Chen et al., 2023 (C23; arXiv:2304.09898), we introduced a new method to directly measure temperature fluctuations and applied it to a nearby dwarf galaxy, Mrk 71, finding a temperature fluctuation parameter $t^2 = 0.008\pm 0.043$. This result is lower by $\sim 2σ$ than the value required to explain the abundance discrepancy (AD) in this object. In the Matters Arising article submitted by Mendez-Delgado et al. (arXiv:2310.01197), the authors claim that using the same data presented in C23 in a different way, it is possible to conclude that the measurements are consistent with a larger $t^2 \simeq 0.1$ inferred indirectly from recombination lines (RLs). However, this requires a higher density such that the infrared [O III] 52 $μ$m and [O III] 88 $μ$m lines -- which form the basis of the direct measurement method -- are mutually inconsistent. Moreover, to reach agreement between the direct $t^2$ measurement and the larger $t^2$ value inferred from RLs requires systematically varying four parameters by $\sim 1σ$ from their best-determined values, which collectively amount to a $\sim2σ$ difference, consistent with the significance ($\sim 2 σ$) originally reported in C23. Therefore, we conclude that the results of C23 hold, and that the combined optical and infrared [O III] data disfavour $t^2 \simeq 0.1$ at the $\approx2σ$ level in Mrk 71. Future work is nonetheless warranted to better understand the AD associated with both optical and infrared emission line analysis.

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arXiv2023

The Ly$α$ non-detection by JWST NIRSpec of a strong Ly$α$ emitter at $z=5.66$ confirmed by MUSE

The detections of Lyman-$α$ ($\rm Lyα$) emission in galaxies with redshifts above 5 are of utmost importance for constraining the cosmic reionization timeline, yet such detections are usually based on slit spectroscopy. Here we investigate the significant bias induced by slit placement on the estimate of $\rm Lyα$ escape fraction ( $f_{\rm esc}^{\mathrm{Lyα}}$), by presenting a galaxy (dubbed A2744-z6Lya) at $z=5.66$ where its deep JWST NIRSpec prism spectroscopy completely misses the strong $\rm Lyα$ emission detected in the MUSE data. A2744-z6Lya exhibits a pronounced UV continuum with an extremely steep spectral slope of $β=-2.574_{-0.008}^{+0.008}$, and it has a stellar mass of $\mathrm{\sim10^{8.82}~M_\odot}$, a star-formation rate of $\mathrm{\sim8.35~M_\odot yr^{-1}}$ and gas-phase metallicity of $\mathrm{12+log\,(O/H)\sim7.88}$. The observed flux and rest-frame equivalent width of its Ly$α$ from MUSE spectroscopy are $1.2\times \rm 10^{-16} erg~s^{-1}cm^{-2}$ and 75Å, equivalent to $f_{\rm esc}^{\mathrm{Lyα}}=78\pm4 \%$. However, its Ly$α$ non-detection from JWST NIRSpec gives a 5-$σ$ upper limit of $<13 \%$, in stark contrast to that derived from MUSE. To explore the reasons for this bias, we perform spatially resolved stellar population analysis of A2744-z6Lya using the JWST NIRCam imaging data to construct 2-dimensional maps of SFR, dust extinction and neutral hydrogen column density. We find that the absence of Ly$α$ in the slit regions probably stems from both the resonance scattering effect of neutral hydrogen and dust extinction. Through analyzing an extreme case in detail, this work highlights the important caveat of inferring $f_{\rm esc}^{\mathrm{Lyα}}$ from slit spectroscopy, particularly when using the JWST multiplexed NIRSpec microshutter assembly.

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arXiv2023

Early results from GLASS-JWST. XXVII. The mass-metallicity relation in lensed field galaxies at cosmic noon with NIRISS

We present a measurement of the mass-metallicity relation (MZR) at cosmic noon, using the JWST near-infrared wide-field slitless spectroscopy obtained by the GLASS-JWST Early Release Science program. By combining the power of JWST and the lensing magnification by the foreground cluster A2744, we extend the measurements of the MZR to the dwarf mass regime at high redshifts. A sample of 50 galaxies with several emission lines is identified across two wide redshift ranges of $z=1.8-2.3$ and $2.6-3.4$ in the stellar mass range of $\log{(M_*/M_\odot)}\in [6.9, 10.0]$. The observed slope of MZR is $0.223 \pm 0.017$ and $0.294 \pm 0.010$ at these two redshift ranges, respectively, consistent with the slopes measured in field galaxies with higher masses. In addition, we assess the impact of the morphological broadening on emission line measurement by comparing two methods of using 2D forward modeling and line profile fitting to 1D extracted spectra. We show that ignoring the morphological broadening effect when deriving line fluxes from grism spectra results in a systematic reduction of flux by $\sim30\%$ on average. This discrepancy appears to affect all the lines and thus does not lead to significant changes in flux ratio and metallicity measurements. This assessment of the morphological broadening effect using JWST data presents, for the first time, an important guideline for future work deriving galaxy line fluxes from wide-field slitless spectroscopy, such as Euclid, Roman, and the Chinese Space Station Telescope.

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