What is the nature of Little Red Dots and what is not, MIRI SMILES edition

2024/01/16 by Pérez-González, Pablo G., Barro, Guillermo, Rieke, George H. +20 · 22 citations
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Instrumentation and Methods for Astrophysics (astro-ph.IM)

paper · doi:10.48550/arxiv.2401.08782

Abstract

We study little red dots (LRD) detected by JADES and covered by the SMILES MIRI survey. Our sample contains 31 sources, ∼70% detected in the two bluest MIRI bands, 40% in redder filters. The median/quartiles redshifts are z=6.9_5.9^7.7 (55% spectroscopic). We analyze the rest-frame ultraviolet through near/mid-infrared spectral energy distributions of LRDs combining NIRCam and MIRI observations, using a variety of modeling techniques that include emission from stars, dust, and (un)obscured active galactic nuclei (AGN). The NIRCam-MIRI colors, for ≥10 μm, are bluer than direct pure emission from AGN tori; the spectral slope flattens in the rest-frame near-infrared, consistent with a 1.6 μm stellar bump. Both observations imply that stellar emission makes the dominant contribution at these wavelengths, expediting a stellar mass estimation: the median/quartiles are log M_⋆/M_\odot=9.4_9.1^9.7. The number density of LRDs is 10^-4.0±0.1 Mpc^-3, accounting for 14±3% of the global population of galaxies with similar redshifts and masses. The flat ultraviolet spectral range is dominated by young stars. The rest-frame near/mid-infrared (2-4 μm) spectral slope reveals significant amounts of dust (bolometric stellar attenuation ∼3-4 mag) heated by strong radiation fields arising from highly embedded compact sources. Our models imply <0.4 kpc heating knots, containing dust-enshrouded OB stars or an AGN producing a similar radiation field, obscured by A(V)>10 mag. We conclude that LRDs are extremely intense and compact starburst galaxies with mass-weighted ages 5-10 Myr, very efficient in producing dust, their global energy output dominated by the direct and dust-recycled emission from OB stars, with some contribution from obscured AGN in the mid-infrared.

Cited by

• Mid-IR luminosity functions: inferred dusty cosmic star-formation and black hole accretion histories from the JWST SMILES
• Spider-Webb: Spatially-Resolved Evidence of Inside-Out Quenching in the Spiderweb Protocluster at z ∼ 2
• Balmer Transition Signatures from Gas-Enshrouded, Dust-Poor Active Galactic Nuclei
• A Black-Hole Envelope Interpretation for Cosmological Demographics of Little Red Dots
• (Re)solving the complex multi-scale morphology and V-shaped SED of a newly discovered strongly-lensed Little Red Dot in Abell 383
• MIRI spectrophotometry of GN-z11: Detection and nature of an optical red continuum component
• Discovery of two little red dots transitioning into quasars
• Little Red Dots as Globular Clusters in Formation
• Mephisto: Self-Improving Large Language Model-Based Agents for Automated Interpretation of Multi-band Galaxy Observations
• JWST provides a new view of cosmic dawn: latest developments in studies of early galaxies
• A z≃0.4 Little Red Dot analog: An Extended Starburst with an Overmassive Black hole
• Limitations on Morphological Fitting for JWST "Little Red Dots"
• Excavating the Ruins: An Ancient <i>z</i> = 2.675 Galaxy Which Formed in the First 500 Myr
• Spectral Uniformity of Little Red Dots: A Natural Outcome of Coevolving Seed Black Holes and Nascent Starbursts
• On the Variability Features of Active Galactic Nuclei in Little Red Dots
• What you see is what you get: empirically measured bolometric luminosities of Little Red Dots
• What Do Radio Emission Constraints Tell Us About Little Red Dots as Tidal Disruption Events?
• Investigating Little Red Dots with UV Excess: Are They the High-Redshift Siblings of Blue Hot DOGs?
• The Missing Hard Photons of Little Red Dots: Their Incident Ionizing Spectra Resemble Massive Stars
• New Insight from the James Webb Space Telescope on Variable Active Galactic Nuclei
• Little Red Dots and their Progenitors from Direct Collapse Black Holes
• CAPERS-LRD-z9: A Gas-enshrouded Little Red Dot Hosting a Broad-line Active Galactic Nucleus at <i>z</i> = 9.288

Related

• A Comprehensive Photometric Selection of `Little Red Dots' in MIRI Fields: An IR-Bright LRD at z=3.1386 with Warm Dust Emission
• Exploring the Nature of Little Red Dots: Constraints on AGN and Stellar Contributions from PRIMER MIRI Imaging
• Not Just a Dot: the complex UV morphology and underlying properties of Little Red Dots
• MEGA: Spectrophotometric SED Fitting of Little Red Dots Detected in JWST MIRI
• Dust in Little Red Dots