Probing the megaparsec-scale environment of hyperluminous infrared galaxies at 2 < z < 4
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Context. Protoclusters are progenitors of galaxy clusters and they serve as an important key in studies of how halo mass and stellar mass assemble in the early universe. Finding the signposts of such overdense regions, such as bright dusty star-forming galaxies (DSFG), is a popular method for identifying protocluster candidates.
Aims. Hyperluminous infrared galaxies (HLIRGs) are ultramassive and show extreme levels of dusty star formation and black hole accretion that are expected to reside in overdense regions with massive halos. We study the megaparsec-scale environment of the largest HLIRG sample to date (526 HLIRGs over 26 deg2) and we investigate whether they are, in fact, predominantly located in overdense regions.
Methods. We first explored the surface density of Herschel 250 μm sources around HLIRGs and made comparisons with the corresponding values around random positions. Then, we compared the spatial distribution of neighbors around HLIRGs with their counterparts around randomly selected galaxies using a deep IRAC-selected catalog with good-quality photometric redshifts. We also used a redshift-matched quasar sample and submillimeter galaxy (SMG) sample to validate our method, as previous clustering studies have measured the host halo masses of these populations. Finally, we adopted a friends of friends (FoF) algorithm to look for (proto)clusters hosting HLIRGs.
Results. We find that HLIRGs tend to have more bright star-forming neighbors (with 250 μm flux density > 10 mJy) within a 100″ projected radius (∼0.8 Mpc at 2 < z < 4), as compared to a random galaxy at a 3.7σ significance. In our 3D analysis, we find relatively weak excess of IRAC-selected sources within 3 Mpc around HLIRGs compared with random galaxy neighbors, mainly influenced by photometric redshift uncertainty and survey depth. We find a more significant difference (at a 4.7σ significance) in the number of Low Frequency Array (LOFAR)-detected neighbors in the deepest ELAIS-N1 (EN1) field. Furthermore, HLIRGs at 3 < z < 4 show stronger excess compared to HLIRGs at 2 < z < 3 (0.13 ± 0.04 and 0.14 ± 0.01 neighbors around HLIRGs and random positions at 2 < z < 3, respectively, and 0.08 ± 0.04 and 0.05 ± 0.01 neighbors around HLIRGs and random positions at 3 < z < 4, respectively), which is consistent with cosmic downsizing. Finally, we present a list of 30 of the most promising protocluster candidates selected for future follow-up observations.
Aims. Hyperluminous infrared galaxies (HLIRGs) are ultramassive and show extreme levels of dusty star formation and black hole accretion that are expected to reside in overdense regions with massive halos. We study the megaparsec-scale environment of the largest HLIRG sample to date (526 HLIRGs over 26 deg2) and we investigate whether they are, in fact, predominantly located in overdense regions.
Methods. We first explored the surface density of Herschel 250 μm sources around HLIRGs and made comparisons with the corresponding values around random positions. Then, we compared the spatial distribution of neighbors around HLIRGs with their counterparts around randomly selected galaxies using a deep IRAC-selected catalog with good-quality photometric redshifts. We also used a redshift-matched quasar sample and submillimeter galaxy (SMG) sample to validate our method, as previous clustering studies have measured the host halo masses of these populations. Finally, we adopted a friends of friends (FoF) algorithm to look for (proto)clusters hosting HLIRGs.
Results. We find that HLIRGs tend to have more bright star-forming neighbors (with 250 μm flux density > 10 mJy) within a 100″ projected radius (∼0.8 Mpc at 2 < z < 4), as compared to a random galaxy at a 3.7σ significance. In our 3D analysis, we find relatively weak excess of IRAC-selected sources within 3 Mpc around HLIRGs compared with random galaxy neighbors, mainly influenced by photometric redshift uncertainty and survey depth. We find a more significant difference (at a 4.7σ significance) in the number of Low Frequency Array (LOFAR)-detected neighbors in the deepest ELAIS-N1 (EN1) field. Furthermore, HLIRGs at 3 < z < 4 show stronger excess compared to HLIRGs at 2 < z < 3 (0.13 ± 0.04 and 0.14 ± 0.01 neighbors around HLIRGs and random positions at 2 < z < 3, respectively, and 0.08 ± 0.04 and 0.05 ± 0.01 neighbors around HLIRGs and random positions at 3 < z < 4, respectively), which is consistent with cosmic downsizing. Finally, we present a list of 30 of the most promising protocluster candidates selected for future follow-up observations.
Date Issued
2022-12-01
Date Acceptance
2022-09-02
Citation
Astronomy and Astrophysics (A & A), 2022, 668
ISSN
0004-6361
Publisher
EDP Sciences
Journal / Book Title
Astronomy and Astrophysics (A & A)
Volume
668
Copyright Statement
© F. Gao et al. 2022. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
10.1051/0004-6361/202244072
Subjects
ACTIVE GALACTIC NUCLEI
Astronomy & Astrophysics
clusters
COSMOLOGY LEGACY SURVEY
DATA RELEASE
FORMATION-DENSITY RELATION
galaxies
general
groups
high-redshift
INTERMEDIATE-REDSHIFT QUASARS
Physical Sciences
PROTO-CLUSTER
Science & Technology
SKY SURVEY
STAR-FORMING GALAXIES
STELLAR MASS
SUBMILLIMETER GALAXIES
Publication Status
Published
Article Number
A54
Date Publish Online
2022-12-01