Abundant Population of Broad H α Emitters in the GOODS-N Field Revealed by CONGRESS, FRESCO, and JADES

We present a spectroscopic search for broad Hα emitters at z ≈ 3.7–6.5 in the GOODS-N field, utilizing JWST/NIRCam slitless spectroscopy from FRESCO and CONGRESS, complemented by JADES imaging. We identify 19 broad Hα emitters with FWHM > 1000 km s−1 at z ≈ 4–5.5, including nine new sources. The broad Hα luminosity function derived from our sample is consistent with those of other JWST-selected broad-line active galactic nuclei (AGN) reported in the literature. The black hole masses and AGN bolometric luminosities inferred from the broad Hα components indicate that most sources are accreting at ∼10% of the Eddington limit. We derive their host stellar masses via spectral energy distribution (SED) fitting and find higher MBH/M* ratios relative to the local MBH–M* relations, consistent with previous studies. We find that 42% of the sample do not satisfy the widely used color selection criteria for little red dots (LRDs), with the majority of these sources lacking the characteristic steep rest-optical red slope, indicating that the LRD selection is highly incomplete when selecting AGN galaxies. A comparison of the average SEDs between our sample and LRDs selected in the same field reveals that the steep red slopes observed in some LRDs are likely due to line-boosting effects as previously suggested. Furthermore, we find that 68% of color-selected LRDs with Hα detections in the NIRCam/grism spectra do not exhibit broad-line features. While the limited sensitivity of the grism spectra may hinder the detection of broad-line components in faint sources, our findings still highlight the enigmatic nature of the LRD population.