How Do Galaxies Trace a Large-scale Structure? A Case Study around a Massive Protocluster at Z = 3.13

Shi, Ke; Huang, Yun; Lee, Kyoung-Soo; Toshikawa, Jun; Bowen, Kathryn N.; Malavasi, Nicola; Lemaux, Brian C.; Cucciati, O.; Fèvre, O. Le; Dey, Arjun

doi:10.3847/1538-4357/ab2118

Cited by 43 publications

(50 citation statements)

References 119 publications

(182 reference statements)

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“…For instance, Shimakawa et al (2017) have found a few Mpc deviation of LAEs' density peak in a z = 2 protocluster from that of Hα-emitting galaxies, which are normal star-forming galaxies commonly seen at high redshifts. A similar offset from continuum-selected galaxies has also been reported (Overzier et al 2008;Toshikawa et al 2016;Shi et al 2019). More importantly, Momose et al (2020) have suggested that the peak of LAEs' distribution does not match that of intergalactic neutral hydrogen (IGM Hi).…”

Section: Introductionsupporting

confidence: 81%

“…Our results also indicate that LAEs may not faithfully trace matter distribution, unlike O3Es and continuumselected galaxies. Some observational studies have found a 3 − 15 h −1 cMpc offset between the overdensity peaks of LAEs and other galaxy populations (Toshikawa et al 2016;Shimakawa et al 2017;Shi et al 2019). Given the anisotropy of Hi density distribution over r = 3 − 5 h −1 cMpc found in this study, the discordance reported by those previous studies can be, at least partly, explained by the selection bias.…”

Section: Discussion and Summarycontrasting

confidence: 52%

“…With its density increasing with matter density, IGM Hi is a faithful tracer of the cosmic web that has recently come into use, although the areas mapped by IGM Hi are still limited because the observations are very time-consuming. These reported discrepancies might imply that LAEs intrinsically avoid dense parts of the cosmic web for some reason (e.g., Shimakawa et al 2017;Oteo et al 2018;Shi et al 2019;Momose et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Catch Me if You Can: Biased Distribution of Ly$α$-emitting Galaxies according to the Viewing Direction

Momose,

Shimasaku,

Nagamine

et al. 2021

Preprint

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We report that Lyα-emitting galaxies (LAEs) may not faithfully trace the cosmic web of neutral hydrogen (Hi), but their distribution is likely biased depending on the viewing direction. We calculate the cross-correlation (CCF) between galaxies and Lyα forest transmission fluctuations on the near and far sides of the galaxies separately, for three galaxy samples at z ∼ 2: LAEs, [Oiii] emitters (O3Es), and continuum-selected galaxies. We find that only LAEs have anisotropic CCFs, with the near side one showing lower signals up to r = 3 − 4 h −1 comoving Mpc. This means that the average Hi density on the near side of LAEs is lower than that on the far-side by a factor of 2.1 under the Fluctuating Gunn-Peterson Approximation. Mock LAEs created by assigning Lyα equivalent width (EW obs Lyα ) values to O3Es with an empirical relation also show similar, anisotropic CCFs if we use only objects with higher EW obs Lyα than a certain threshold. These results indicate that galaxies on the far side of a dense region are more difficult to be detected ("hidden") in Lyα because Lyα emission toward us is absorbed by dense neutral hydrogen. If the same region is viewed from a different direction, a different set of LAEs will be selected as if galaxies are playing hide-and-seek using Hi gas. Care is needed when using LAEs to search for overdensities.

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Section: Introductionsupporting

confidence: 81%

Section: Discussion and Summarycontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

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Catch Me if You Can: Biased Distribution of Ly$α$-emitting Galaxies according to the Viewing Direction

Momose,

Shimasaku,

Nagamine

et al. 2021

Preprint

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“…Deep narrow-band imaging surveys have recently demonstrated the utility of Lyα emission as tracers of the large-scale structure in the distant universe. Massive protocluster sites are found to be significant overdensities of LAEs (Steidel et al 2000;Lee et al 2014b;Bȃdescu et al 2017;Shi et al 2019a). In several protoclusters, filamentary structures traced by LAEs stretch out tens of Mpcs from a protocluster (Matsuda et al 2005;Dey et al 2016a), mirroring the expectation of dark matter structures around a cluster-sized halo.…”

Section: Introductionmentioning

confidence: 99%

The Role of Dust, UV Luminosity and Large-scale Environment on the Escape of Lya Photons: A Case Study of a Protocluster field at z = 3.1

Huang,

Lee,

Shi

et al. 2021

Preprint

Self Cite

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We present a detailed characterization of the Lyα properties for 93 Lyα emitters (LAEs) at z ∼ 3.1 selected from the D1 field of the Canada-France-Hawaii-Telescope Legacy Survey, including 24 members of a massive protocluster. The median-stacked Lyα image shows an extended Lyα halo (LAH) surrounding the galaxy with the exponential scale length 4.9 ± 0.7kpc, which accounts for roughly half of the total line flux. Accounting for the LAH contribution, the total Lyα escape fraction, f esc , is 40 ± 26%. Combining the dataset with existing measurements, we find a dependence of f esc on the galaxy's UV slope (β) and UV luminosity (L UV ). The simultaneous use of both parameters allows prediction of f esc within 0.18dex, a substantial improvement over 0.23dex when only β is used. The correlation between f esc and E(B −V ) suggests that Lyα photons undergo interstellar dust attenuation in a similar manner to continuum photons. Yet, Lyα transmission is typically higher than that expected for continuum photons at similar wavelength by a factor, which depends on UV luminosity, up to 2 in the samples we studied. These results hint at complex geometries and physical conditions of the interstellar medium, which affect the Lyα transmission or production. Alternatively, the dust law may change with luminosity leading to over-or under-estimation of f esc . Finally, we report that protocluster member LAEs tend to be bluer and more UV-luminous than their field cousins, resulting in systematically higher f esc values. We speculate that it may be due to the widespread formation of young low-mass galaxies in dense gas-rich environments.

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“…The spatial distribution of ELGs in overdense regions, can be used to infer the underlying dark matter (DM) distribution, and how galaxy properties relate to the environment in which they reside (Mo et al 2004;Cooray 2005;Overzier et al 2006;Orsi et al 2016;Ota et al 2018;Shi et al 2019;Gonzalez-Perez et al 2020). In particular, the way in which the environment of protoclusters affects the emission of ELG at high redshift is still a matter of debate (see Overzier 2016, for a review).…”

Section: Introductionmentioning

confidence: 99%

Are Ly α emitters segregated in protoclusters regions?

Hough

Gurung-López

Orsi

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The presence of neutral hydrogen in the inter-stellar medium (ISM) and inter-galactic medium (IGM) induces radiative transfer (RT) effects on Lyα photons which affect the observability of Lyα emitters (LAEs). We use the galform semi-analytic model of galaxy formation and evolution to analyse how these effects shape the spatial distribution of LAEs with respect to Hα emitters (HAEs) around high density regions at high redshift. We find that when a large sample of protoclusters is considered, HAEs showing also Lyα emission (HAEs+LAEs) populate the same regions as those that do not display the Lyα line at z = 2.2. We compare against the protocluster USS1558-003, one of the most massive protoclusters located at z = 2.53. Our results indicate that the strong depletion of HAEs+LAEs present in the high density regions of USS1558-003 may be due to cosmic variance. We find that at z = 2.2 and z = 3.0, RT of the ISM produces a strong decline (30-50 per cent) of the clustering amplitude of HAEs+LAEs with respect to HAEs towards the protoclusters centre. At z = 5.7, given the early evolutionary state of protoclusters and galaxies, the clustering of HAEs+LAEs has a smaller variation (10-20 per cent) towards the protoclusters centre. Depending on the equivalent width and luminosity criteria of the emission-line galaxy sample, the IGM can have a mild or a null effect on galaxy properties and clustering in high density regions.

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How Do Galaxies Trace a Large-scale Structure? A Case Study around a Massive Protocluster at Z = 3.13

Cited by 43 publications

References 119 publications

Catch Me if You Can: Biased Distribution of Ly$α$-emitting Galaxies according to the Viewing Direction

Catch Me if You Can: Biased Distribution of Ly$α$-emitting Galaxies according to the Viewing Direction

The Role of Dust, UV Luminosity and Large-scale Environment on the Escape of Lya Photons: A Case Study of a Protocluster field at z = 3.1

Are Ly α emitters segregated in protoclusters regions?

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