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Abstract:

Strong gravitational-lensing systems with multiple source planes are powerful tools for probing the density profiles and dark matter substructure of galaxies. The ratio of the Einstein radii is related to the dark energy equation of state through the cosmological scaling factor β . Galaxy-scale double-source-plane lenses (DSPLs) are extremely rare, however. We report the discovery of four new galaxy-scale DSPL candidates in the Euclid Quick Release 1 (Q1) data. These systems were initially identified through a combination of machine-learning lens-finding models and subsequent visual inspection from citizens and experts. We applied the widel -used LensPop lens-forecasting model to predict that the full Euclid survey will discover 1700 DSPLs. This scales to 6 ± 3 DSPLs in 63 deg 2 , which is the area of Q1. The number of discoveries in this work is broadly consistent with this forecast. We present lens models for each DSPL and infer their β values. Our initial Q1 sample demonstrates that Euclid promises to discover these rare objects.

Abstract:

We present the first results of the JWST Emission Line Survey (JELS). Utilizing the first NIRCam narrow-band imaging at 4.7 m, over 63 arcmin in the PRIMER/COSMOS field, we have identified 609 emission line galaxy candidates. From these, we robustly selected 35 H star-forming galaxies at , with H star-formation rates () of . Combining our unique H sample with the exquisite panchromatic data in the field, we explored their physical properties and star-formation histories, and compared these to a broad-band selected sample at which has offered vital new insights into the nature of high-redshift galaxies. UV-continuum slopes () were considerably redder for our H sample () compared to the broad-band sample (). This was not due to dust attenuation as our H sample was relatively dust-poor (median ); instead, we argue that the reddened slopes could be due to nebular continuum. We compared and the UV-continuum-derived to SED-fitted measurements averaged over canonical time-scales of 10 and 100 Myr ( and ). We found an increase in recent SFR for our sample of H emitters, particularly at lower stellar masses (). We also found that strongly traces SFR averaged over 10 Myr time-scales, whereas the UV-continuum overpredicts SFR on 100 Myr time-scales at low stellar masses. These results point to our H sample undergoing ‘bursty’ star formation. Our F356W sample showed a larger scatter in across all stellar masses, which has highlighted how narrow-band photometric selections of H emitters are key to quantifying the burstiness of star-formation activity.