arXiv subjects

Patricia Bolan

Publications and source records attributed to Patricia Bolan.

6 recordsLinked to original sources

arXiv2024

Ly$α$ Emission Strength and Stellar Properties of Faint Galaxies from $5 < z < 8.2$

We present a study on stellar properties of Lyman-alpha (Ly$α$) emitters at 5 $< z <$ 8.2. We use 247 photometrically-selected, lensed, high-redshift, low luminosity galaxy candidates with spectroscopic follow-up. Of these, 38 are confirmed spectroscopically to be between 5 $< z <$ 8.2 via detection of Ly$α$. For each galaxy and candidate, we estimate stellar mass, star formation rate, specific star formation rate, and mass-weighted age with spectral energy distribution fitting. We also measure the UV $β$ slope and luminosity using values from photometry. We find no strong correlation between Ly$α$ equivalent width and any of these properties, as well as no significant difference between the physical properties of Ly$α$ emitters and candidates without Ly$α$ detected. This lack of expected trends may be explained by a combination of the evolving opacity of the IGM at these redshifts as well as the unique phase space probed by our lensed sample. Via tests on other galaxy samples which show varying strengths of correlations, we conclude that if there exist any relationships between Ly$α$ EW and physical properties in the underlying population of faint galaxies, they are weak correlations. We also present the results of a spectroscopic search for CIII] emission in confirmed Ly$α$ emitters at $z \sim 7$, finding no CIII] detections, but putting constraints on strong AGN activity and extreme nebular emission.

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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

Early Results from GLASS-JWST XXIII: The transmission of Lyman-alpha from UV-faint z ~ 3-6 galaxies

Lyman-alpha (Ly$α$) emission from galaxies can be used to trace neutral hydrogen in the epoch of reionization, however, there is a degeneracy between the attenuation of Ly$α$ in the intergalactic medium (IGM) and the line profile emitted from the galaxy. Large shifts of Ly$α$ redward of systemic due to scattering in the interstellar medium can boost Ly$α$ transmission in the IGM during reionization. The relationship between Ly$α$ velocity offset from systemic and other galaxy properties is not well-established at high-redshift or low luminosities, due to the difficulty of observing emission lines which trace systemic redshift. Rest-frame optical spectroscopy with JWST/NIRSpec has opened a new window into understanding of Ly$α$ at z>3. We present a sample of 12 UV-faint galaxies ($-20 \lesssim$ MUV $\lesssim -16$) at $3 \lesssim z \lesssim 6$, with Ly$α$ velocity offsets, $Δv_{\mathrm{Ly}α}$, measured from VLT/MUSE and JWST/NIRSpec from the GLASS-JWST Early Release Program. We find median $Δv_{\mathrm{Ly}α}$ of 205 km s$^{-1}$ and standard deviation 75 km s$^{-1}$, compared to 320 and 170km s$^{-1}$ for MUV < -20 galaxies in the literature. Our new sample demonstrates the previously observed trend of decreasing Ly$α$ velocity offset with decreasing UV luminosity and optical line velocity dispersion, extends to MUV $\gtrsim$ -20, consistent with a picture where the Ly$α$ profile is shaped by gas close to the systemic redshift. Our results imply that during reionization Ly$α$ from UV-faint galaxies will be preferentially attenuated, but that detecting Ly$α$ with low $Δv_{\mathrm{Ly}α}$ can be an indicator of large ionized bubbles.

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arXiv2023

JWST reveals a possible $z \sim 11$ galaxy merger in triply-lensed MACS0647$-$JD

MACS0647$-$JD is a triply-lensed $z\sim11$ galaxy originally discovered with the Hubble Space Telescope. Here we report new JWST imaging, which clearly resolves MACS0647$-$JD as having two components that are either merging galaxies or stellar complexes within a single galaxy. Both are very small, with stellar masses $\sim10^8\,M_\odot$ and radii $r<100\,\rm pc$. The brighter larger component "A" is intrinsically very blue ($β\sim-2.6$), likely due to very recent star formation and no dust, and is spatially extended with an effective radius $\sim70\,\rm pc$. The smaller component "B" appears redder ($β\sim-2$), likely because it is older ($100-200\,\rm Myr$) with mild dust extinction ($A_V\sim0.1\,\rm mag$), and a smaller radius $\sim20\,\rm pc$. We identify galaxies with similar colors in a high-redshift simulation, finding their star formation histories to be out of phase. With an estimated stellar mass ratio of roughly 2:1 and physical projected separation $\sim400\,\rm pc$, we may be witnessing a galaxy merger 400 million years after the Big Bang. We also identify a candidate companion galaxy C $\sim3\,{\rm kpc}$ away, likely destined to merge with galaxies A and B. The combined light from galaxies A+B is magnified by factors of $\sim$8, 5, and 2 in three lensed images JD1, 2, and 3 with F356W fluxes $\sim322$, $203$, $86\,\rm nJy$ (AB mag 25.1, 25.6, 26.6). MACS0647$-$JD is significantly brighter than other galaxies recently discovered at similar redshifts with JWST. Without magnification, it would have AB mag 27.3 ($M_{UV}=-20.4$). With a high confidence level, we obtain a photometric redshift of $z=10.6\pm0.3$ based on photometry measured in 6 NIRCam filters spanning $1-5\rmμm$, out to $4300\,Å$ rest-frame. JWST NIRSpec observations planned for January 2023 will deliver a spectroscopic redshift and a more detailed study of the physical properties of MACS0647$-$JD.

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arXiv2021

Inferring the IGM Neutral Fraction at z ~ 6-8 with Low-Luminosity Lyman Break Galaxies

We present a Bayesian inference on the neutral hydrogen fraction of the intergalactic medium (IGM), $x_{\textrm{HI}}$, at $z \sim$ 6-8 using the properties of Lyman break galaxies during the Epoch of Reionization. We use large samples of LBG candidates at $5.5 \leq z \leq 8.2$ with spectroscopy from Keck/DEIMOS and Keck/MOSFIRE. For each galaxy, we incorporate either the Lyman-$α$ equivalent width (EW) for detections or the EW limit spectrum for nondetections to parameterize the EW distribution at various ultraviolet brightnesses for a given redshift. Using our reference sample of galaxy candidates from the ionized universe at $z$ $\sim$ 6.0, we are able to infer $x_{\textrm{HI}}$ at two redshifts: $z$ $\sim$ 6.7 and $z$ $\sim$ 7.6. This work includes intrinsically faint, gravitationally lensed galaxies at $z$ $\sim$ 6.0 in order to constrain the intrinsic faint-end Ly$α$ EW distribution and provide a comparable population of galaxies to counterparts in our sample that are at higher redshift. The inclusion of faint galaxy candidates, in addition to a more sophisticated modelling framework, allows us to better isolate effects of the interstellar medium and circumgalactic medium on the observed Lyman-$α$ distribution from those of the IGM. We infer an upper limit of $x_{\textrm{HI}}$ $\leq$ 0.25 at $z$ = 6.7 $\pm$ 0.2 and a neutral fraction of $x_{\textrm{HI}}$ = $0.83^{+0.08}_{-0.11}$ at $z$ = 7.6$\pm$ 0.6, both within 1$σ$ uncertainty, results which favor a moderately late and rapid reionization.

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arXiv2021

RELICS-DP7: Spectroscopic Confirmation of a Dichromatic Primeval Galaxy at z ~ 7

We report the discovery of a spectroscopically-confirmed strong Lyman-$α$ emitter at $z=7.0281\pm0.0003$, observed as part of the Reionization Cluster Lensing Survey (RELICS). This galaxy, dubbed "Dichromatic Primeval Galaxy" at $z\sim7$ (DP7), shows two distinct components. While fairly unremarkable in terms of its ultraviolet (UV) luminosity ($\sim0.3L^{\ast}_{UV}$, where $L^{\ast}_{UV}$ is the characteristic luminosity), DP7 has one of the highest observed Lyman-$α$ equivalent widths (EWs) among Lyman-$α$ emitters at $z>6$ ($>200$ Angstrom in the rest frame). The strong Lyman-$α$ emission generally suggests a young metal-poor, low-dust galaxy; however, we find that the UV slope $β$ of the galaxy as a whole is redder than typical star-forming galaxies at these redshifts, $-1.13\pm 0.84$, likely indicating, on average, a considerable amount of dust obscuration, or an older stellar population. When we measure $β$ for the two components separately, however, we find evidence of differing UV colors, suggesting two separate stellar populations. Also, we find that Lyman-$α$ is spatially extended and likely larger than the galaxy size, hinting to the possible existence of a Lyman-$α$ halo. Rejuvenation or merging events could explain these results. Either scenario requires an extreme stellar population, possibly including a component of Population III stars, or an obscured Active Galactic Nucleus. DP7, with its low UV luminosity and high Lyman-$α$ EW, represents the typical galaxies that are thought to be the major contribution to the reionization of the Universe, and for this reason DP7 is an excellent target for follow-up with the James Webb Space Telescope.

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