A giant protocluster of galaxies at redshift 5.7 (original) (raw)
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A massive protocluster of galaxies at a redshift of z ≈ 5.3
Nature, 2011
shown along with model fits . Error bars are 1σ including standard measurement error and systematic flux calibration error. The optical, near and mid-infrared, and radio data are taken from the COSMOS survey , with newly acquired warm IRAC data used at 3.6 and 4.5μm. The 0.87 and 1.1mm fluxes are taken from the sub-mm imaging survey 14,15 , wile the 2mm data point presented here was acquired with the GISMO camera on the IRAM 30m telescope. The 2.7, 3.3, and 8.2mm flux limits are from the CO 6-5, 5-4, and 2-1 measurements 8 . The best-fit stellar mass is 1.0±0.3 x10 10 solar masses with A v =0.8 and an age of 10Myr. The best fit Far-Infrared (60-120μm) luminosity ranges from 0.9-3.2 x10 13 solar luminosities depending on the model assumptions. However, the 3mm upper limits, the radio flux limit, and the CO luminosity favor lower luminosities.
The Astrophysical Journal, 2010
We present three candidate clusters of galaxies at redshifts most likely between 1.7 and 2.0, which corresponds to a fundamentally unexplored epoch of clusters evolution. The candidates were found by studying the environment around our newly selected sample of "beacons" low-luminosity (FR I) radio galaxies in the COSMOS field. In this way we intend to use the fact that FRI at low z are almost invariably located in clusters of galaxies. We use the most accurate photometric redshifts available to date, derived by the COSMOS collaboration using photometry with a set of 30 filters, to look for three-dimensional space over-densities around our objects. Three out of the five FR Is in our sample which possess reliable photometric redshifts between z phot = 1.7 and 2.0 display overdensities that together are statistically significant at the 4σ level, compared to field counts, arguing for the presence of rich clusters of galaxies in their Mpc environment. These first results show that the new method for finding high-z clusters we recently proposed, which makes use of low power FR I radio galaxies instead of the more powerful FR II sources often used in the literature to date, is returning very promising candidates.
Protoclusters at 𝓏 = 5.7: a view from the MultiDark galaxies
Monthly Notices of the Royal Astronomical Society, 2020
Protoclusters, which will yield galaxy clusters at lower redshift, can provide valuable information on the formation of galaxy clusters. However, identifying progenitors of galaxy clusters in observations is not an easy task, especially at high redshift. Different priors have been used to estimate the overdense regions that are thought to mark the locations of protoclusters. In this paper, we use mimicked Ly α-emitting galaxies at z = 5.7 to identify protoclusters in the MultiDark galaxies, which are populated by applying three different semi-analytic models to the 1,h−1,rmGpc1\, h^{-1}\, {\rm Gpc}1,h−1,rmGpc MultiDark Planck2 simulation. To compare with observational results, we extend the criterion 1 (a Ly α luminosity limited sample) to criterion 2 (a match to the observed mean galaxy number density). To further statistically study the finding efficiency of this method, we enlarge the identified protocluster sample (criterion 3) to about 3500 at z = 5.7 and study their final mass distribution. The n...
Galaxy protocluster candidates at 1.6< z≲ 2
Astronomy & …, 2010
We present a study of protoclusters associated with high redshift radio galaxies. We imaged MRC 1017-220 (z = 1.77) and MRC 0156-252 (z = 2.02) using the near-infrared wide-field (7.5 ′ ×7.5 ′ ) imager VLT/HAWK-I in the Y, H and K s bands. We present the first deep Y-band galaxy number counts within a large area (∼200 arcmin 2 ). We then develop a purely near-infrared colour selection technique to isolate galaxies at 1.6 < z < 3 that may be associated with the two targets, dividing them into (i) red passively evolving or dusty star-forming galaxies or (ii) blue/star-formation dominated galaxies with little or no dust. Both targeted fields show an excess of starforming galaxies with respect to control fields. No clear overdensity of red galaxies is detected in the surroundings of MRC 1017-220 although the spatial distribution of the red galaxies resembles a filament-like structure within which the radio galaxy is embedded. In contrast, a significant overdensity of red galaxies is detected in the field of MRC 0156-252, ranging from a factor of ∼ 2 − 3 times the field density at large scales (2.5 Mpc, angular distance) up to a factor of ∼ 3 − 4 times the field density within a 1 Mpc radius of the radio galaxy. Half of these red galaxies have colours consistent with red sequence models at z ∼ 2, with a large fraction being bright (K s < 21.5, i.e. massive). In addition, we also find a small group of galaxies within 5 ′′ of MRC 0156-252 suggesting that the radio galaxy has multiple companions within ∼ 50 kpc. We conclude that the field of MRC0156-252 shows many remarkable similarities with the well-studied protocluster surrounding PKS1138-262 (z=2.16) suggesting that MRC 0156-252 is associated with a galaxy protocluster at z ∼ 2.
Galaxy protocluster candidates around z˜ 2.4 radio galaxies
Monthly Notices of The Royal Astronomical Society, 2011
We study the environments of six radio galaxies at 2.2 < z < 2.6 using wide-field near-infrared images. We use colour cuts to identify galaxies in this redshift range, and find that three of the radio galaxies are surrounded by significant surface overdensities of such galaxies. The excess galaxies that comprise these overdensities are strongly clustered, suggesting they are physically associated. The colour distribution of the galaxies responsible for the overdensity is consistent with those of galaxies that lie within a narrow redshift range at z˜ 2.4. Thus the excess galaxies are consistent with being companions of the radio galaxies. The overdensities have estimated masses in excess of 1014 M⊙, and are dense enough to collapse into virialized structures by the present day; these structures may evolve into groups or clusters of galaxies. A flux-limited sample of protocluster galaxies with K < 20.6 mag is derived by statistically subtracting the foreground and background galaxies. The colour distribution of the protocluster galaxies is bimodal, consisting of a dominant blue sequence, comprising 77 ± 10 per cent of the galaxies and a poorly populated red sequence. The blue protocluster galaxies have similar colours to local star-forming irregular galaxies (U-VAB˜ 0.6), suggesting that most protocluster galaxies are still forming stars at the observed epoch. The blue colours and lack of a dominant protocluster red sequence imply that these cluster galaxies form the bulk of their stars at z≲ 3.
A large population of ‘Lyman-break’ galaxies in a protocluster at redshift z ≈ 4.1
Nature, 2004
The most massive galaxies and the richest clusters are believed to have emerged from regions with the largest enhancements of mass density 1−4 relative to the surrounding space. Distant radio galaxies may pinpoint the locations of the ancestors of rich clusters, because they are massive systems associated with overdensities of galaxies that are bright in the Lymanα line of hydrogen 5−7 . A powerful technique for detecting high-redshift galaxies is to search for the characteristic 'Lyman break' feature in the galaxy colour, at wavelengths just shortwards of Lyα, due to absorption of radiation from the galaxy by the intervening galactic medium. Here we report multicolour imaging of the most distant candidate 7−9 protocluster, TN J1338-1942 at a redshift z ≈ 4.1. We find a large number of objects with the characteristic colours of galaxies at that redshift, and we show that this excess is concentrated around the targeted dominant radio galaxy. Our data therefore indicate that TN J1338-1942 is indeed the most distant 1
Spectroscopic Confirmation of a Protocluster at z = 3.37 with a High Fraction of Quiescent Galaxies
The Astrophysical Journal, 2022
We report the discovery of MAGAZ3NE J095924+022537, a spectroscopically confirmed protocluster at z = 3.3665 − 0.0012 + 0.0009 around a spectroscopically confirmed UVJ-quiescent ultramassive galaxy (UMG; M ⋆ = 2.34 − 0.34 + 0.23 × 10 11 M ⊙ ) in the COSMOS UltraVISTA field. We present a total of 38 protocluster members (14 spectroscopic and 24 photometric), including the UMG. Notably, and in marked contrast to protoclusters previously reported at this epoch that have been found to contain predominantly star-forming members, we measure an elevated fraction of quiescent galaxies relative to the coeval field ( 73.3 − 16.9 + 26.7 % versus 11.6 − 4.9 + 7.1 % for galaxies with stellar mass M ⋆ ≥ 1011 M ⊙). This high quenched fraction provides a striking and important counterexample to the seeming ubiquitousness of star-forming galaxies in protoclusters at z > 2 and suggests, rather, that protoclusters exist in a diversity of evolutionary states in the early universe. We discuss the pos...
A large population of 'Lyman-break'galaxies in a protocluster at redshift z ≈ 4.1
Nature, 2004
The most massive galaxies and the richest clusters are believed to have emerged from regions with the largest enhancements of mass density 1−4 relative to the surrounding space. Distant radio galaxies may pinpoint the locations of the ancestors of rich clusters, because they are massive systems associated with overdensities of galaxies that are bright in the Lymanα line of hydrogen 5−7 . A powerful technique for detecting high-redshift galaxies is to search for the characteristic 'Lyman break' feature in the galaxy colour, at wavelengths just shortwards of Lyα, due to absorption of radiation from the galaxy by the intervening galactic medium. Here we report multicolour imaging of the most distant candidate 7−9 protocluster, TN J1338-1942 at a redshift z ≈ 4.1. We find a large number of objects with the characteristic colours of galaxies at that redshift, and we show that this excess is concentrated around the targeted dominant radio galaxy. Our data therefore indicate that TN J1338-1942 is indeed the most distant 1
The Astrophysical Journal
We have obtained three-dimensional maps of the universe in ∼ 200×200×80 comoving Mpc 3 (cMpc 3) volumes each at z = 5.7 and 6.6 based on a spectroscopic sample of 179 galaxies that achieves 80% completeness down to the Lyα luminosity of log(L Lyα /[erg s −1 ]) = 43.0, based on our Keck and Gemini observations and the literature. The maps reveal filamentary large-scale structures and two remarkable overdensities made out of at least 44 and 12 galaxies at z = 5.692 (z57OD) and z = 6.585 (z66OD), respectively, making z66OD the most distant overdensity spectroscopically confirmed to date with > 10 spectroscopically confirmed galaxies. We compare spatial distributions of submillimeter galaxies at z 4 − 6 with our z = 5.7 galaxies forming the large-scale structures, and detect a 99.97% signal of cross correlation, indicative of a clear coincidence of dusty star-forming galaxy and dust unobscured galaxy formation at this early epoch. The galaxies in z57OD and z66OD are actively forming stars with star formation rates (SFRs) 5 times higher than the main sequence, and particularly the SFR density in z57OD is 10 times higher than the cosmic average at the redshift (a.k.a. the Madau-Lilly plot). Comparisons with numerical simulations suggest that z57OD and z66OD are protoclusters that are progenitors of the present-day clusters with halo masses of ∼ 10 14 M .
A Millimeter Continuum Survey for Massive Protoclusters in the Outer Galaxy
The Astrophysical Journal Supplement Series, 2005
Our search for the earliest stages of massive star formation turned up twelve massive pre-protocluster candidates plus a few protoclusters. For this search, we selected 47 FIR-bright IRAS sources in the outer Galaxy. We mapped regions of several square arcminutes around the IRAS source in the millimeter continuum in order to find massive cold cloud cores possibly being in a very early stage of massive star formation. Masses and densities are derived for the 128 molecular cloud cores found in the obtained maps. We present these maps together with near-infrared, mid-infrared, and radio data collected from the 2MASS, MSX, and NVSS catalogs. Further data from the literature on detections of high-density tracers, outflows, and masers are added. The multi-wavelength datasets are used to characterize each observed region. The massive cloud cores (M > 100 M ⊙ ) are placed in a tentative evolutionary sequence depending on their emission at the investigated wavelengths. Candidates for the youngest stages of massive star formation are identified by the lack of detections in the above-mentioned nearinfrared, mid-infrared, and radio surveys. Twelve massive cores prominent in the millimeter continuum fulfill this requirement. Since neither FIR nor radio emission have been detected from these cloud cores massive protostars must be very deeply embedded in these cores. Some of these objects may actually Pre-Proto-cluster cores: an up to now rare object class, where the initial conditions of massive star formation can be studied.