Galaxy formation and evolution

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.

Abstract:

We present a sample of 341 “little red dots” (LRDs) spanning the redshift range z ∼ 2-11 using data from the CEERS, PRIMER, JADES, UNCOVER, and NGDEEP surveys. Unlike past use of color indices to identify LRDs, we employ continuum slope fitting using shifting bandpasses to sample the same rest-frame emission blueward and redward of the Balmer break. This enables the detection of LRDs over a wider redshift range and with less contamination from galaxies with strong breaks that otherwise lack a rising red continuum. The redshift distribution of our sample increases at z < 8 and then undergoes a rapid decline at z ∼ 4.5, which may tie the emergence of these sources to the inside-out growth that galaxies experience during this epoch. We find that LRDs are ∼1 dex more numerous than X-ray- and UV-selected active galactic nuclei (AGN) at z ∼ 5-7. Within our sample, we have identified the first two X-ray-detected LRDs. An X-ray spectral analysis confirms that these AGN are moderately obscured with log ( N H / cm 2 ) of 23 . 3 − 1.3 + 0.4 and 22.7 2 − 0.16 + 0.13 . Our analysis reveals that reddened AGN emission dominates their rest-optical light, while the rest-UV originates from their host galaxies. We also present NIRSpec observations from the RUBIES survey of 17 LRDs that show broad emission lines consistent with AGN activity. The confirmed AGN fraction of our sample is 71% for sources with F444W < 26.5. In addition, we find three LRDs with blueshifted Balmer absorption features in their spectra, suggesting an outflow of high-density, low-ionization gas from near the central engine of these faint, red AGN.

Abstract:

Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows only a small amount of scattered light from the obscured quasar to escape, enabling the decomposition of the stellar component from the total flux. The presence of scattered light enables the redshift of the source and the properties of the black hole to be obtained from the Sloan Digital Sky Survey (SDSS) and SDSS-related literature. From WISE and SDSS data, we select 11 hyperluminous Hot DOGs at z = 1.5–3.7 with bolometric luminosities Lbol ≳ 1047 erg s−1. We investigate the MBH–M⋆ relation in these sources using Bayesian spectral energy distribution fitting or with extra constraints from Hubble Space Telescope image decomposition. Stellar masses are successfully derived for eight Hot DOGs. We find high Eddington ratios λEdd in these Hot DOGs, with the median value of 1.05 and the maximum value close to 3. The super-Eddington accretion may be associated with the overdense environments of Hot DOGs. We find no significant differences in the MBH/M⋆ of these Hot DOGs compared to the local relation, suggesting that these dust-obscured quasars are the progenitors of massive early-type galaxies. We speculate that the subsequent evolution of Hot DOGs may be significantly influenced by active galactic nucleus feedback and remain on the local relation.