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1. The MOSFIRE Deep Evolution Field Survey: Implications of the Lack of Evolution in the Dust Attenuation–Mass Relation to z ∼ 2*

   https://doi.org/10.3847/1538-4357/ac4742  

   Shapley, Alice E.; Sanders, Ryan L.; Salim, Samir; Reddy, Naveen A.; Kriek, Mariska; Mobasher, Bahram; Coil, Alison L.; Siana, Brian; Price, Sedona H.; Shivaei, Irene; et al (February 2022, The Astrophysical Journal)

   Abstract We investigate the relationship between dust attenuation and stellar mass ( M * ) in star-forming galaxies over cosmic time. For this analysis, we compare measurements from the MOSFIRE Deep Evolution Field survey at z ∼ 2.3 and the Sloan Digital Sky Survey (SDSS) at z ∼ 0, augmenting the latter optical data set with both UV Galaxy Evolution Explorer (GALEX) and mid-infrared Wide-field Infrared Survey Explorer (WISE) photometry from the GALEX-SDSS-WISE Catalog. We quantify dust attenuation using both spectroscopic measurements of H α and H β emission lines, and photometric measurements of the rest-UV stellar continuum. The H α /H β ratio is used to determine the magnitude of attenuation at the wavelength of H α , A H α . Rest-UV colors and spectral energy distribution fitting are used to estimate A 1600 , the magnitude of attenuation at a rest wavelength of 1600 Å. As in previous work, we find a lack of significant evolution in the relation between dust attenuation and M * over the redshift range z ∼ 0 to z ∼ 2.3. Folding in the latest estimates of the evolution of M dust , ( M dust / M gas ), and gas surface density at fixed M * , we find that the expected M dust and dust mass surface density are both significantly higher at z ∼ 2.3 than at z ∼ 0. These differences appear at odds with the lack of evolution in dust attenuation. To explain the striking constancy in attenuation versus M * , it is essential to determine the relationship between metallicity and ( M dust / M gas ), the dust mass absorption coefficient and dust geometry, and the evolution of these relations and quantities from z ∼ 0 to z ∼ 2.3. 

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2. First Observations of the Brown Dwarf HD 19467 B with JWST

   https://doi.org/10.3847/1538-4357/acb68b  

   Greenbaum, Alexandra Z.; Llop-Sayson, Jorge; Lew, Ben W.P.; Bryden, Geoffrey; Roellig, Thomas L.; Ygouf, Marie; Fulton, B. J.; Hey, Daniel R.; Huber, Daniel; Mukherjee, Sagnick; et al (March 2023, The Astrophysical Journal)

   Abstract We observed HD 19467 B with JWST’s NIRCam in six filters spanning 2.5–4.6 μ m with the long-wavelength bar coronagraph. The brown dwarf HD 19467 B was initially identified through a long-period trend in the radial velocity of the G3V star HD 19467. HD 19467 B was subsequently detected via coronagraphic imaging and spectroscopy, and characterized as a late-T type brown dwarf with an approximate temperature ∼1000 K. We observed HD 19467 B as a part of the NIRCam GTO science program, demonstrating the first use of the NIRCam Long Wavelength Bar coronagraphic mask. The object was detected in all six filters (contrast levels of 2 × 10 −4 to 2 × 10 −5 ) at a separation of 1.″6 using angular differential imaging and synthetic reference differential imaging. Due to a guide star failure during the acquisition of a preselected reference star, no reference star data were available for post-processing. However, reference differential imaging was successfully applied using synthetic point-spread functions developed from contemporaneous maps of the telescope’s optical configuration. Additional radial velocity data (from Keck/HIRES) are used to constrain the orbit of HD 19467 B. Photometric data from TESS are used to constrain the properties of the host star, particularly its age. NIRCam photometry, spectra, and photometry from the literature, and improved stellar parameters are used in conjunction with recent spectral and evolutionary substellar models to derive the physical properties of HD 19467 B. Using an age of 9.4 ± 0.9 Gyr inferred from spectroscopy, Gaia astrometry, and TESS asteroseismology, we obtain a model-derived mass of 62 ± 1 M J , which is consistent within 2 σ with the dynamically derived mass of 81 − 12 + 14 M J . 

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3. Looking for Obscured Young Star Clusters in NGC 1313

   https://doi.org/10.3847/1538-4357/abe0b5  

   Messa, Matteo; Calzetti, Daniela; Adamo, Angela; Grasha, Kathryn; Johnson, Kelsey E.; Sabbi, Elena; Smith, Linda J.; Bajaj, Varun; Finn, Molly K.; Lin, Zesen (March 2021, The Astrophysical Journal)

   Abstract Using recently acquired Hubble Space Telescope NIR observations ( J , Pa β , and H bands) of the nearby galaxy NGC 1313, we investigate the timescales required by a young star cluster to emerge from its natal cloud. We search for extincted star clusters, potentially embedded in their natal cloud as either (1) compact sources in regions with high H α /Pa β extinctions or (2) compact H ii regions that appear as point-like sources in the Pa β emission map. The NUV–optical–NIR photometry of the candidate clusters is used to derive their ages, masses, and extinctions via a least- χ 2 spectral energy distribution broad- and narrowband fitting process. The 100 clusters in the final samples have masses in the range and moderate extinctions, E ( B − V ) ≲ 1.0 mag. Focusing on the young clusters (0–6 Myr), we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, E ( B − V ) < 0.25 mag, already at very young ages (≤3 Myr), suggesting that dust is quickly removed from clusters. A stronger correlation is found between the morphology of the nebular emission (compact, partial or absent, both in H α and Pa β ) and cluster age. Relative fractions of clusters associated with a specific nebular morphology are used to estimate the typical timescales for clearing the natal gas cloud, resulting in between 3 and 5 Myr, ∼1 Myr older than what was estimated from NUV–optical-based cluster studies. This difference hints at a bias for optical-only-based studies, which James Webb Space Telescope will address in the coming years. 

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4. High-Cadence TESS and Ground-based Data of SN 2019esa, the Less Energetic Sibling of SN 2006gy ^∗

   https://doi.org/10.3847/1538-4357/ac8ea7  

   Andrews, Jennifer E.; Pearson, Jeniveve; Lundquist, M. J.; Sand, David J.; Jencson, Jacob E.; Bostroem, K. Azalee; Hosseinzadeh, Griffin; Valenti, S.; Smith, Nathan; Amaro, R. C.; et al (October 2022, The Astrophysical Journal)

   Abstract We present photometric and spectroscopic observations of the nearby ( D ≈ 28 Mpc) interacting supernova (SN) 2019esa, discovered within hours of explosion and serendipitously observed by the Transiting Exoplanet Survey Satellite (TESS). Early, high-cadence light curves from both TESS and the DLT40 survey tightly constrain the time of explosion, and show a 30 day rise to maximum light followed by a near-constant linear decline in luminosity. Optical spectroscopy over the first 40 days revealed a reddened object with narrow Balmer emission lines seen in Type IIn SNe. The slow rise to maximum in the optical light curve combined with the lack of broad H α emission suggest the presence of very optically thick and close circumstellar material (CSM) that quickly decelerated the SN ejecta. This CSM was likely created from a massive star progenitor with an M ̇ ∼ 0.2 M ☉ yr −1 lost in a previous eruptive episode 3–4 yr before eruption, similar to giant eruptions of luminous blue variable stars. At late times, strong intermediate-width Ca ii , Fe i , and Fe ii lines are seen in the optical spectra, identical to those seen in the superluminous interacting SN 2006gy. The strong CSM interaction masks the underlying explosion mechanism in SN 2019esa, but the combination of the luminosity, strength of the H α lines, and mass-loss rate of the progenitor seem to be inconsistent with a Type Ia CSM model and instead point to a core-collapse origin. 

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5. CLEAR: Paschen-β Star Formation Rates and Dust Attenuation of Low-redshift Galaxies

   https://doi.org/10.3847/1538-4357/ac5a4c  

   Cleri, Nikko J.; Trump, Jonathan R.; Backhaus, Bren E.; Momcheva, Ivelina; Papovich, Casey; Simons, Raymond; Weiner, Benjamin; Estrada-Carpenter, Vicente; Finkelstein, Steven L.; Giavalisco, Mauro; et al (April 2022, The Astrophysical Journal)

   Abstract We use Paschen- β (Pa β ; 1282 nm) observations from the Hubble Space Telescope G141 grism to study the star formation and dust-attenuation properties of a sample of 29 low-redshift ( z < 0.287) galaxies in the CANDELS Ly α Emission at Reionization survey. We first compare the nebular attenuation from Pa β /H α with the stellar attenuation inferred from the spectral energy distribution, finding that the galaxies in our sample are consistent with an average ratio of the continuum attenuation to the nebular gas of 0.44, but with a large amount of excess scatter beyond the observational uncertainties. Much of this scatter is linked to a large variation between the nebular dust attenuation as measured by (space-based) Pa β to (ground-based) H α to that from (ground-based) H α /H β . This implies there are important differences between attenuation measured from grism-based/wide-aperture Pa β fluxes and the ground-based/slit-measured Balmer decrement. We next compare star formation rates (SFRs) from Pa β to those from dust-corrected UV. We perform a survival analysis to infer a census of Pa β emission implied by both detections and nondetections. We find evidence that galaxies with lower stellar mass have more scatter in their ratio of Pa β to attenuation-corrected UV SFRs. When considering our Pa β detection limits, this observation supports the idea that lower-mass galaxies experience “burstier” star formation histories. Together, these results show that Pa β is a valuable tracer of a galaxy’s SFR, probing different timescales of star formation and potentially revealing star formation that is otherwise missed by UV and optical tracers. 

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