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  • 1
    Online Resource
    Online Resource
    A First Look at Spatially Resolved Balmer Decrements at 1.0 〈 z 〈 2.4 from JWST NIRISS Slitless Spectroscopy
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 949, No. 1 ( 2023-05-01), p. L11-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 949, No. 1 ( 2023-05-01), p. L11-
    Abstract: We present the first results on the spatial distribution of dust attenuation at 1.0 〈 z 〈 2.4 traced by the Balmer decrement, H α /H β , in emission-line galaxies using deep JWST NIRISS slitless spectroscopy from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). H α  and H β  emission-line maps of emission-line galaxies are extracted and stacked in bins of stellar mass for two grism redshift bins, 1.0 〈 z grism 〈 1.7 and 1.7 〈 z grism 〈 2.4. Surface brightness profiles for the Balmer decrement are measured and radial profiles of the dust attenuation toward  H α , A H α , are derived. In both redshift bins, the integrated Balmer decrement increases with stellar mass. Lower-mass (7.6 ≤ Log( M * / M ⊙ ) 〈 10.0) galaxies have centrally concentrated, negative dust attenuation profiles whereas higher-mass galaxies (10.0 ≤ Log( M * / M ⊙ ) 〈 11.1) have flat dust attenuation profiles. The total dust obscuration is mild, with on average 0.07 ± 0.07 and 0.14 ± 0.07 mag in the low- and high-redshift bins respectively. We model the typical light profiles of star-forming galaxies at these redshifts and stellar masses with GALFIT and apply both uniform and radially varying dust attenuation corrections based on our integrated Balmer decrements and radial dust attenuation profiles. If the H α  star formation rates (SFRs) of these galaxies were measured after slit-loss corrections assuming uniform dust attenuation with typical JWST NIRSpec slit spectroscopy (0.″2 × 0.″5 shutters), the total SFR will be overestimated by 6% ± 21% and 26% ± 9% at 1.0 ≤ z 〈 1.7 and 1.7 ≤ z 〈 2.4 respectively.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/acd1db
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 2
    Online Resource
    Online Resource
    An Extremely Compact, Low-mass Galaxy on its Way to Quiescence at z = 5.2
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 949, No. 2 ( 2023-06-01), p. L23-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 949, No. 2 ( 2023-06-01), p. L23-
    Abstract: We report the discovery of a low-mass z = 5.200 ± 0.002 galaxy that is in the process of ceasing its star formation. The galaxy, MACS0417-z5BBG, is multiply imaged with magnification factors ∼40 by the galaxy cluster MACS J0417.5-1154, observed as part of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using observations of MACS0417-z5BBG with a JWST/NIRSpec Prism spectrum and NIRCam imaging, we investigate the mechanism responsible for the cessation of star formation of the galaxy and speculate about possibilities for its future. Using spectrophotometric fitting, we find a remarkably low stellar mass of M * = 4.3 ± 0.8 0.9 × 10 7 M ⊙ , less than 1% of the characteristic stellar mass at z ∼ 5. We measure a delensed rest-UV half-light radius in the source plane of 30 ± 5 7 pc and measure a star formation rate from H α of 0.14 ± 0.12 0.17 M ⊙ yr −1 . We find that under the assumption of a double power-law star formation history, MACS0417-z5BBG has seen a recent rise in star formation, peaking ∼10–30 Myr ago and declining precipitously since then. Together, these measurements reveal a low-mass, extremely compact galaxy which is in the process of ceasing star formation. We investigate the possibilities of mechanisms that have led to the cessation of star formation in MACS0417-z5BBG, considering stellar and active galactic nuclei (AGN) feedback and environmental processes. We can likely rule out most environmental processes but leave open the possibility of a low-mass AGN that does not leave a broad-line imprint on the spectrum or that MACS0417-z5BBG could be a star-forming galaxy in the lull of a bursty star formation history.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/acd457
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 3
    Online Resource
    Online Resource
    The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWST
    American Astronomical Society ; 2022
    In:  The Astrophysical Journal Letters Vol. 937, No. 2 ( 2022-10-01), p. L35-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 937, No. 2 ( 2022-10-01), p. L35-
    Abstract: Using data from JWST, we analyse the compact sources (“sparkles”) located around a remarkable z spec = 1.378 galaxy (the ‘Sparkler) that is strongly gravitationally lensed by the z = 0.39 galaxy cluster SMACS J0723.3-7327. Several of these compact sources can be cross-identified in multiple images, making it clear that they are associated with the host galaxy. Combining data from JWSTs Near-Infrared Camera (NIRCam) with archival data from the Hubble Space Telescope (HST), we perform 0.4–4.4 μ m photometry on these objects, finding several of them to be very red and consistent with the colors of quenched, old stellar systems. Morphological fits confirm that these red sources are spatially unresolved even in the strongly magnified JWST/NIRCam images, while the JWST/NIRISS spectra show [O iii ] λ 5007 emission in the body of the Sparkler but no indication of star formation in the red compact sparkles. The most natural interpretation of these compact red companions to the Sparkler is that they are evolved globular clusters seen at z = 1.378. Applying Dense Basis spectral energy distribution fitting to the sample, we infer formation redshifts of z form ∼ 7–11 for these globular cluster candidates, corresponding to ages of ∼3.9–4.1 Gyr at the epoch of observation and a formation time just ∼0.5 Gyr after the Big Bang. If confirmed with additional spectroscopy, these red, compact sparkles represent the first evolved globular clusters found at high redshift, which could be among the earliest observed objects to have quenched their star formation in the universe, and may open a new window into understanding globular cluster formation. Data and code to reproduce our results will be made available at http://canucs-jwst.com/sparkler.html .
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/ac90ca
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 4
    Online Resource
    Online Resource
    Non-blackbody Disks Can Help Explain Inferred AGN Accretion Disk Sizes
    American Astronomical Society ; 2018
    In:  The Astrophysical Journal Vol. 854, No. 2 ( 2018-02-20), p. 93-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 854, No. 2 ( 2018-02-20), p. 93-
    Abstract: If the atmospheric density in the accretion disk of an active galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can produce a non-blackbody emergent spectrum. For a given bolometric luminosity, at ultraviolet and optical wavelengths such disks have lower fluxes and apparently larger sizes as compared to disks that emit as blackbodies. We show that models in which is a sufficiently low fixed fraction of the interior density ρ can match the AGN STORM observations of NGC 5548 but produce disk spectral energy distributions that peak at shorter wavelengths than observed in luminous AGN in general. Thus, scattering atmospheres can contribute to the explanation for large inferred AGN accretion disk sizes but are unlikely to be the only contributor. In the appendix section, we present unified equations for the interior ρ and T in gas pressure-dominated regions of a thin accretion disk.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/aaa768
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2018
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 5
    Online Resource
    Online Resource
    JWST catches the assembly of a z ∼ 5 ultra-low-mass galaxy
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society: Letters Vol. 523, No. 1 ( 2023-04-27), p. L40-L45
    Details
    In: Monthly Notices of the Royal Astronomical Society: Letters, Oxford University Press (OUP), Vol. 523, No. 1 ( 2023-04-27), p. L40-L45
    Abstract: Using CANUCS imaging we found an apparent major merger of two $z$ ∼ 5 ultra-low-mass galaxies (M⋆∼107M⊙ each) that are doubly imaged and magnified ∼12–15× by the lensing cluster MACS 0417. Both galaxies are experiencing young (∼100 Myr), synchronised bursts of star formation with log (sSFR/Gyr−1) ∼1.3–1.4, yet SFRs of just ∼0.2M⊙ yr−1. They have sub-solar (Z ∼ 0.2Z⊙) gas-phase metallicities and are connected by an even more metal-poor star-forming bridge. The galaxy that forms from the merger will have a mass of at least M⋆∼2 × 107 M⊙, at least half of it formed during the interaction-induced starburst. More than half of the ionizing photons produced by the system (before and during the merger) will have been produced during the burst. This system provides the first detailed look at a merger involving two high-$z$ ultra-low-mass galaxies of the type believed to be responsible for reionizing the Universe. It suggests that such galaxies can grow via a combination of mass obtained through major mergers, merger-triggered starbursts, and long-term in-situ star formation. If such high-$z$ mergers are common, then merger-triggered starbursts could be significant contributors to the ionizing photon budget of the Universe.
    Type of Medium: Online Resource
    ISSN: 1745-3925 , 1745-3933
    URL: Article
    DOI: 10.1093/mnrasl/slad054
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2190759-6
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