arXiv subjects

I. Goovaerts

Publications and source records attributed to I. Goovaerts.

3 recordsLinked to original sources

arXiv2025

Resolving dust and Ly{\alpha} emission in a lensed galaxy at the epoch of reionization with JWST/CANUCS

Lyman $\alpha$ emission is highly sensitive to dust and neutral hydrogen and is therefore expected to be strongly suppressed in dusty or gas-rich galaxies during the epoch of reionization (EoR). Nevertheless, numerous moderately dusty Ly$\alpha$ emitters (LAEs) are observed at this epoch, suggesting that complex interstellar medium (ISM) geometries and feedback-driven outflows may facilitate Ly$\alpha$ escape. We investigate the dust, gas, and stellar properties of the gravitationally lensed LAE HCM 6A at $z=6.5676$ to characterize its multiphase ISM and the physical conditions regulating Ly$\alpha$ escape. We combine JWST/NIRISS slitless spectroscopy, HST+JWST/NIRCam imaging, and JWST/NIRSpec slit spectra from the CANUCS program. Using a customized BAGPIPES SED-fitting framework with a flexible attenuation law, we derive stellar, nebular, and dust properties on integrated ($\sim$kpc), slit-level ($\sim$0.1 kpc), and pixel-level ($\sim$25 pc) scales, enabled by strong lensing ($\mu \approx 8.3$-$9.1$). A Ly$\alpha$ map from SLEUTH traces the spatial distribution of Ly$\alpha$ emission. We measure an unlensed stellar mass of $\log M_\ast = 8.3$-$8.4$ and an intrinsic UV magnitude of $M_{\rm UV} = -19.8 \pm 0.1$. The older region (S1) is moderately dusty with consistent stellar and nebular attenuation indicators, implying a uniform ISM geometry, while the youngest region (S3) shows strong discrepancies among dust tracers, indicating a feedback-shaped multiphase ISM. Ly$\alpha$ emission arises primarily from S3, where a dust-cleared central clump enables efficient Ly$\alpha$ escape. We find Calzetti-like attenuation curves with a UV bump that strengthens with stellar age and decreasing $A_V$. Our observations provide a uniquely detailed, spatially resolved view of a moderately dusty LAE during the EoR, demonstrating how feedback and multiphase ISM structure govern Ly$\alpha$ escape.

astro-ph.GA↗

arXiv2024

Galaxy main sequence and properties of low-mass Lyman-alpha Emitters towards reionisation viewed by VLT/MUSE and JWST/NIRCam

Faint, star-forming galaxies likely play a dominant role in cosmic reionisation. Strides have been made in recent years to characterise these populations at high redshifts ($z>3$). Now for the first time, with JWST photometry beyond 1$\,μm$ in the rest frame, we can derive accurate stellar masses and position these galaxies on the galaxy main sequence. We seek to assess the place of 96 individual Lyman-alpha emitters (LAEs) selected behind the A2744 lensing cluster with MUSE spectroscopy on the galaxy main sequence. We also compare derived stellar masses to Lyman-alpha luminosities and equivalent widths to better quantify the relationship between the Lyman-alpha emission and the host galaxy. These 96 LAEs lie in the redshift range $2.9<z<6.7$, and their range of masses extends down to $10^6\,\mathrm{M_{\odot}}$ (over half with $\mathrm{M_{\star}}<10^8\,\mathrm{M_{\odot}}$). We use the JWST/NIRCam and HST photometric catalogs from the UNCOVER project, giving us excellent wavelength coverage from $450\,\mathrm{nm}$ to $4.5\,μm$. We find a main sequence relation for these low mass LAEs of the form: $\mathrm{log\,SFR}=(0.88\pm0.07 - 0.030\pm0.027\times t)\,\mathrm{log\,M_{\star}} - ( 6.31\pm0.41 - 0.08\pm0.37\times t)$. This is in approximate agreement with best-fits of previous collated studies, however, with a steeper slope and a higher normalisation. This indicates that low-mass LAEs towards the epoch of reionisation lie above typical literature main sequence relations derived at lower redshift and higher masses. Additionally, comparing our results to UV-selected samples, we see that while low-mass LAEs lie above these typical main sequence relations, they are likely not singular in this respect at these masses and redshifts. While low-mass galaxies have been shown to play a significant role in cosmic reionisation, our results point to no special position for LAEs in this regard.

astro-ph.GA↗

arXiv2024

Linking UV spectral properties of MUSE Ly-alpha emitters at z>3 to Lyman continuum escape

The physical conditions giving rise to high escape fractions of ionizing radiation (LyC $f_{\rm{esc}}$) in star-forming galaxies - most likely protagonists of cosmic reionization - are not yet fully understood. Using the VLT/MUSE observations of ~1400 Ly$α$ emitters at 2.9 < z < 6.7, we compare stacked rest-frame UV spectra of candidates for LyC leakers and non-leakers selected based on their Ly$α$ profiles. We find that the stacks of potential LyC leakers, i.e. galaxies with narrow, symmetric Ly$α$ profiles with small peak separation, generally show (i) strong nebular OIII]1666, [SiIII]1883, and [CIII]1907+CIII]1909 emission, indicating a high-ionization state of the interstellar medium (ISM); (ii) high equivalent widths of HeII1640 (~1-3 A), suggesting the presence of hard ionizing radiation fields; (iii) SiII*1533 emission, revealing substantial amounts of neutral hydrogen off the line of sight; (iv) high CIV1548,1550 to [CIII]1907+CIII]1909 ratios (CIV/CIII] > 0.75), signalling the presence of low column density channels in the ISM. In contrast, the stacks with broad, asymmetric Ly$α$ profiles with large peak separation show weak nebular emission lines, low HeII1640 equivalent widths (<1 A), and low CIV/CIII] (<0.25), implying low-ionization states and high-neutral hydrogen column densities. Our results suggest that CIV/CIII] might be sensitive to the physical conditions that govern LyC photon escape, providing a promising tool for identification of ionizing sources among star-forming galaxies in the epoch of reionization.

astro-ph.GA↗