SCUBA-2 follow-up of Herschel-SPIRE observed Planck overdensities

Mackenzie, T.; Scott, Douglas; Bianconi, Matteo; Clements, D. L.; Dole, H.; Flores-Cacho, I.; Guery, David; Kneißl, R.; Lagache, G.; Marleau, F.; Montier, L.; Nesvadba, N. P. H.; Pointecouteau, É.; Soucail, G.

doi:10.1093/mnras/stx512

Cited by 21 publications

(24 citation statements)

References 46 publications

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“…The photometric redshift distribution of all the sources in these 13 candidate protoclusters is shown in Fig 6, in black. The results from MacKenzie et al (2017) are also shown in magenta; this consists of 46 PHz sources (Planck Collaboration et al 2016c) with Herschel overdensities, likely in protoclusters. It can be seen that a significant fraction of our sources lie in the range 2 < z < 3, which is consistent with the expected peak of cosmic star-formation rate density either in protoclusters or in the field (Clements et al 2014;Madau & Dickinson 2014).…”

Section: Sed Fitting and Photometric Redshiftsmentioning

confidence: 95%

“…Nonetheless, a significant number of sources in our candidate protoclusters have infrared luminosities in the same range as the peak in PCL1002. Sources in MacKenzie et al (2017) tend to be more luminous. We conclude that the 850 µm sources in our candidate protoclusters are as luminous as those of known protoclusters (such as PCL1002), and have representitave infrared luminosities just below 10 13 L .…”

Section: Infrared Luminosities and Star-formation Ratesmentioning

confidence: 99%

“…As discussed in Section 3.3, we estimate the infrared luminosity and SFR for each SCUBA-2 source by integrating the SED from 8 to 1,000 µm (see Table B1). Fig 7 shows the L IR distribution for all the sources in our 13 candidate protoclusters, compared with a known DSFG-rich protocluster at z ∼2, PCL1002, and sources in candidate protoclusters from MacKenzie et al (2017). We have scaled the number of sources to per arcminute 2 in order to compare fields with different areas.…”

Section: Infrared Luminosities and Star-formation Ratesmentioning

confidence: 99%

“…Photometric redshift distribiton of sources in 13 candidate protocluster fields in this paper (black), a known DSFG-rich protocluster at z ∼2, PCL1002 (cyan), 256 sources in the COS-MOS field in the S2CLS survey (red), and sources from another Planck -based prototcluster candidate survey (magenta,MacKenzie et al 2017). z > 6 sources are not included because their photometry no longer covers the peak of the redshifted SED, and their photometric redshifts are considered not robust.…”

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confidence: 96%

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SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE

Cheng

Clements

Greenslade

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present SCUBA-2 850-µm observations of 13 candidate starbursting protoclusters selected using Planck and Herschel data. The cumulative number counts of the 850-µm sources in 9/13 of these candidate protoclusters show significant overdensities compared to the field, with the probability <10 −2 assuming the sources are randomly distributed in the sky. Using the 250-, 350-, 500-and 850-µm flux densities, we estimate the photometric redshifts of individual SCUBA-2 sources by fitting spectral energy distribution (SED) templates with an MCMC method. The photometric redshift distribution, peaking at 2 < z < 3, is consistent with that of known z > 2 protoclusters and the peak of the cosmic star-formation rate density (SFRD). We find that the 850µm sources in our candidate protoclusters have infrared luminosities of L IR 10 12 L and star-formation rates of SFR=(500-1,500)M yr −1 . By comparing with results in the literature considering only Herschel photometry, we conclude that our 13 candidate protoclusters can be categorised into four groups: six of them being high-redshift starbursting protoclusters, one being a lower-redshift cluster/protocluster, three being protoclusters that contain lensed DSFG(s) or are rich in 850-µm sources, and three regions without significant Herschel or SCUBA-2 source overdensities. The total SFRs of the candidate protoclusters are found to be comparable or higher than those of known protoclusters, suggesting our sample contains some of the most extreme protocluster population. We infer that cross-matching Planck and Herschel data is a robust method for selecting candidate protoclusters with overdensities of 850-µm sources.

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Section: Sed Fitting and Photometric Redshiftsmentioning

confidence: 95%

Section: Infrared Luminosities and Star-formation Ratesmentioning

confidence: 99%

Section: Infrared Luminosities and Star-formation Ratesmentioning

confidence: 99%

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confidence: 96%

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SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE

Cheng

Clements

Greenslade

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The submillimetre (submm) window has become an important waveband for extragalatic astronomy due to the discovery of bright submm galaxies (SMGs). These galaxies appear to be among the earliest and most actively star-forming galaxies in the Universe, often reaching luminosities of more E-mail: rhliu@phas.ubc.ca than 10 13 L (over 100 times that of our Milky Way galaxy) and star-formation rates (SFRs) greater than a few hundred M yr −1 (e.g., Blain et al 2002;Magnelli et al 2012;Swinbank et al 2014;MacKenzie et al 2017;Micha lowski et al 2017) around redshifts 2-3, corresponding to only a few billion years after the Big Bang (e.g., Chapman et al 2005;Simpson et al 2014Simpson et al , 2017.…”

Section: Introductionmentioning

confidence: 99%

A machine-learning approach for identifying the counterparts of submillimetre galaxies and applications to the GOODS-North field

Liu

Hill

Scott

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Identifying the counterparts of submillimetre (submm) galaxies (SMGs) in multiwavelength images is a critical step towards building accurate models of the evolution of strongly star-forming galaxies in the early Universe. However, obtaining a statistically significant sample of robust associations is very challenging due to the poor angular resolution of single-dish submm facilities. Recently, a large sample of single-dish-detected SMGs in the UKIDSS UDS field, a subset of the SCUBA-2 Cosmology Legacy Survey (S2CLS), was followed up with the Atacama Large Millimeter/submillimeter Array (ALMA), which has provided the resolution necessary for identification in optical and near-infrared images. We use this ALMA sample to develop a training set suitable for machine-learning (ML) algorithms to determine how to identify SMG counterparts in multiwavelength images, using a combination of magnitudes and other derived features. We test several ML algorithms and find that a deep neural network performs the best, accurately identifying 85 per cent of the ALMA-detected optical SMG counterparts in our cross-validation tests. When we carefully tune traditional colour-cut methods, we find that the improvement in using machine learning is modest (about 5 per cent), but importantly it comes at little additional computational cost. We apply our trained neural network to the GOODS-North field, which also has single-dish submm observations from the S2CLS and deep multiwavelength data but little high-resolution interferometric submm imaging, and we find that we are able to classify SMG counterparts for 36/67 of the single-dish submm sources. We discuss future improvements to our ML approach, including combining ML with spectral energy distribution-fitting techniques and using longer wavelength data as additional features.

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Using ALMA to resolve the nature of the early star-forming large-scale structure PLCK G073.4−57.5

Kneißl

Polletta

Martinache

et al. 2019

A&A

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Galaxy clusters at high redshift are key targets for understanding matter assembly in the early Universe, yet they are challenging to locate. A sample of more than 2000 high-z candidate structures has been found using Planck's all-sky submillimetre maps, and a sub-set of 234 have been followed up with Herschel-SPIRE, which showed that the emission can be attributed to large overdensities of dusty star-forming galaxies. As a next step, we need to resolve and characterise the individual galaxies giving rise to the emission seen by Planck and Herschel, and to find out whether they constitute the progenitors of present-day, massive galaxy clusters. Thus, we targeted the eight brightest Herschel-SPIRE sources in the centre of the Planck peak PLCK G073.4−57.5 using ALMA at 1.3 mm, and complemented these observations with multi-wavelength data from Spitzer-IRAC, CFHT-WIRCam in the J and K s bands, and JCMT's SCUBA-2 instrument. We detected a total of 18 millimetre galaxies brighter than 0.3 mJy within the 2.4 arcmin 2 ALMA pointings, corresponding to an ALMA source density 8-30 times higher than average background estimates and larger than seen in typical 'proto-cluster' fields. We were able to match all but one of the ALMA sources to a near infrared (NIR) counterpart. The four most significant SCUBA-2 sources are not included in the ALMA pointings, but we find an 8 σ stacking detection of the ALMA sources in the SCUBA-2 map at 850 µm. We derive photometric redshifts, infrared (IR) luminosities, star-formation rates (SFRs), stellar masses (M), dust temperatures, and dust masses for all of the ALMA galaxies. Photometric redshifts identify two groups each of five sources, concentrated around z 1.5 and 2.4. The two groups show two 'red sequences', that is similar near-IR [3.6] − [4.5] colours and different J − K s colours. The majority of the ALMA-detected galaxies are on the SFR versus M main sequence (MS), and half of the sample is more massive than the characteristic M * at the corresponding redshift. We find that the z 1.5 group has total SFR = 840 +120 −100 M yr −1 and M = 5.8 +1.7 −2.4 × 10 11 M , and that the z 2.4 group has SFR = 1020 +310 −170 M yr −1 and M = 4.2 +1.5 −2.1 × 10 11 M , but the latter group is more scattered in stellar mass and around the MS. Serendipitous CO line detections in two of the galaxies appear to match their photometric redshifts at z = 1.54. We performed an analysis of star-formation efficiencies (SFEs) and CO-and mm-continuum-derived gas fractions of our ALMA sources, combined with a sample of 1 < z < 3 cluster and proto-cluster members, and observed trends in both quantities with respect to stellar masses and in comparison to field galaxies. A dedicated Herschel (Pilbratt et al. 2010) follow-up programme with the SPIRE instrument for 234 Planck targets (Planck Collab. XXXVII 2015) found a significant excess of 'red' sources (where red means S 350 / S 250 > 0.7 and S 500 / S 350 > 0.6, which is consistent with z > ∼ 2 SFGs), in comparison to reference SPIRE fields. Assuming a single com...

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SCUBA-2 follow-up of Herschel-SPIRE observed Planck overdensities

Cited by 21 publications

References 46 publications

SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE

SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE

A machine-learning approach for identifying the counterparts of submillimetre galaxies and applications to the GOODS-North field

Using ALMA to resolve the nature of the early star-forming large-scale structure PLCK G073.4−57.5

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