Narrowband selected high-redshift galaxy candidates contaminated by lower redshift [OIII] ultra-strong emitter line galaxies

Pénin, Aurélie; Cuby, Jean-Gabriel; Clément, Benjamin; Hibon, Pascale; Kneib, Jean-Paul; Cassata, P.; Ilbert, O.

doi:10.1051/0004-6361/201425183

Cited by 7 publications

(5 citation statements)

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“…We note that ELG30 has the highest equivalent width (EW) emission line of our sample, and that would suggest that it is an [Oiii] emitter since they in general have large EW (see e.g. Pénin et al 2015). Further insight into the redshift of ELG30 comes from Fig.…”

Section: Photometric Redshiftsmentioning

confidence: 72%

Emission-line-selected galaxies atz= 0.6–2 in GOODS South: Stellar masses, SFRs, and large-scale structure

Kochiashvili

Møller

Milvang-Jensen

et al. 2015

A&A

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We have obtained deep NIR narrow and broad (J and Y) band imaging data of the GOODS-South field. The narrow band filter is centered at 1060 nm corresponding to redshifts z = 0.62, 1.15, 1.85 for the strong emission lines Hα, [Oiii]/Hβ and [Oii], respectively. From those data we extract a well defined sample (M(AB) = 24.8 in the narrow band) of objects with large emission line equivalent widths in the narrow band. Via SED fits to published broad band data we identify which of the three lines we have detected and assign redshifts accordingly. This results in a well defined, strong emission line selected sample of galaxies down to lower masses than can easily be obtained with only continuum flux limited selection techniques. We compare the (SED fitting-derived) main sequence of star-formation (MS) of our sample to previous works and find that it has a steeper slope than that of samples of more massive galaxies. We conclude that the MS steepens at lower (below M = 10 9.4 M ) galaxy masses. We also show that the SFR at any redshift is higher in our sample. We attribute this to the targeted selection of galaxies with large emission line equivalent widths, and conclude that our sample forms the upper boundary of the MS. We briefly investigate and outline how samples with accurate redshifts down to those low stellar masses open a new window to study the formation of large scale structure in the early universe. In particular we report on the detection of a young galaxy cluster at z = 1.85 which features a central massive galaxy which is the candidate of an early stage cD galaxy, and we identify a likely filament mapped out by [Oiii] and Hβ emitting galaxies at z = 1.15.

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Section: Photometric Redshiftsmentioning

confidence: 72%

Emission-line-selected galaxies atz= 0.6–2 in GOODS South: Stellar masses, SFRs, and large-scale structure

Kochiashvili

Møller

Milvang-Jensen

et al. 2015

A&A

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“…Indeed, recent spectroscopic studies have shown that most of the interlopers that contaminated z ∼ 8 samples are at z ∼ 2 (e.g., Pénin et al 2014;Brammer et al 2013;Hayes et al 2012). For all objects, the best-fit SED has a significantly larger χ 2 and for three of them requires higher dust reddening than in the previous case.…”

Section: Sed-fittingmentioning

confidence: 90%

Frontier Fields: Combining HST, VLT, andSpitzerdata to explore thez~ 8 Universe behind the lensing cluster MACSJ0416.1−2403

Laporte

Streblyanska

Kim

et al. 2015

A&A

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Context. The Hubble Space Telescope (HST) Frontier Fields (HFFs) project started at the end of 2013 with the aim of providing extremely deep images of six massive galaxy clusters. One of the main goals of this program is to push several telescopes to their limits to provide the best current view of the earliest stages of the Universe. The analysis of the initial data has already demonstrated the huge capabilities of the program. Aims. We present a detailed analysis of z ∼ 8 objects behind the HFFs lensing cluster, MACSJ0416.1-2403, combining 0.3−1.6 µm imaging from HST, ground-based K s imaging from VLT HAWK-I, and 3.6 µm and 4.5 µm Spitzer Space Telescope. The images probe to 5σ depths of ≈29 AB for HST, 25.6 AB for HAWK-I, and ≈0.310 and 0.391 µJy at 3.6 and 4.5 µm, respectively. With these datasets, we assess the photometric properties of z ∼ 8 galaxies in this field, as well as their distribution in luminosity, to unprecedented sensitivity. Methods. We applied the classical Lyman break (LB) technique, which combines non detection criteria in bands blueward of the Lyman break at z ∼ 8 and color-selection in bands redward of the break. To avoid contamination by mid-z interlopers, we required a strong break between optical and near-infrared data. We determined the photometric properties of z ∼ 8 selected candidates using spectral energy distribution (SED)-fitting with standard library templates. The luminosity function at z ∼ 8 is computed using a Monte-Carlo method taking advantage of the SED-fitting results. A piece of cautionary information is gleaned from new deep optical photometry of a previously identified z ∼ 8 galaxy in this cluster, which is now firmly detected as a mid-z interloper with a strong ≈1.5 mag Balmer break (between F606W and F125W). Using the SED of this interloper, we estimated the contamination rate of our MACSJ0416.1−2403 sample, and that of previous samples in Abell 2744 that were based on HFF data, we highlight the dangers of pushing the LB technique too close to the photometry limits. Results. Our selection reliably recovers four objects with m F160W ranging from 26.0 to 27.9 AB that are located in modestamplification regions (µ < 2.4). Two of the objects display a secondary break between the IRAC 3.6 µm and 4.5 µm bands, which could be associated to the Balmer break or emission lines at z ∼ 8. The SED-fitting analysis suggests that all of these objects favor high-z solutions with no reliable secondary solutions. The candidates generally have star formation rates around ∼10 M /yr and sizes ranging from 0.2 to 0.5 kpc, which agrees well with previous observations and expectations for objects in the early Universe. The sample size and luminosity distribution are consistent with previous findings.

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“…Alternatively, the Lyman break colors can also be mimicked by extremely strong emission lines in z = 1 − 3 star-forming galaxies (e.g., Atek et al 2011Atek et al , 2014avan der Wel et al 2011). In this class of galaxies the contribution of the emission line flux to the total broadband flux is about 25% on average and can reach 85% (Atek et al 2011) and can have important implications, not only for the high-redshift galaxy selection, but also on the age and stellar mass derived from SED fitting (Schaerer & de Barros 2009;Wilkins et al 2013;Schenker et al 2014a;Pénin et al 2015;Huang et al 2015). In our case, the contamination of one band can lead to an artificial Lyman break, because the faint continuum remains undetected blueward of the break.…”

Section: Sources Of Contaminationmentioning

confidence: 99%

ARE ULTRA-FAINT GALAXIES ATz= 6–8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS

Atek

Richard

Jauzac

et al. 2015

ApJ

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211

229

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We use deep Hubble Space Telescope imaging of the Frontier Fields to accurately measure the galaxy rest-frame ultraviolet luminosity function (UV LF) in the redshift range z ∼ 6-8. We combine observations in three lensing clusters, A2744, MACS 0416, and MACS 0717, and their associated parallelfields to select high-redshift dropout candidates. We use the latest lensing models to estimate the flux magnification and the effective survey volume in combination with completeness simulations performed in the source plane. We report the detection of 227 galaxy candidates at z = 6-7 and 25 candidates at z ∼ 8. While the total survey area is about 4 arcmin 2 in each parallel field, it drops to about 0.6-1 arcmin 2 in the cluster core fields because of the strong lensing. We compute the UV LF at z ∼ 7 using the combined galaxy sample and perform Monte Carlo simulations to determine the best-fit Schechter parameters. We are able to reliably constrain the LF down to an absolute magnitude of M UV = −15.25, which corresponds to 0.005 L å . More importantly, we find that the faint-end slope remains steep down to this magnitude limit with 2.04 . Our results confirm the most recent results in deep blank fields but extend the LF measurements more than two magnitudes deeper. The UV LF at z ∼ 8 is not very well constrained below M UV = −18 owing to the small number statistics and incompleteness uncertainties. To assess the contribution of galaxies to cosmic reionization, we derive the UV luminosity density at z ∼ 7 by integrating the UV LF down to an observational limit of M UV = −15. We show that our determination of log(ρ UV ) = 26.2 ± 0.13 (erg s −1 Hz −1 Mpc −3 ) can be sufficient to maintain reionization with an escape fraction of ionizing radiation of f esc = 10%-15%. Future Hubble Frontier Fields observations will certainly improve the constraints on the UV LF at the epoch of reionization, paving the way to more ambitious programs using cosmic telescopes with the next generation of large aperture telescopes such as the James Webb Space Telescope and the European Extremely Large Telescope.

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Narrowband selected high-redshift galaxy candidates contaminated by lower redshift [OIII] ultra-strong emitter line galaxies

Cited by 7 publications

References 50 publications

Emission-line-selected galaxies atz= 0.6–2 in GOODS South: Stellar masses, SFRs, and large-scale structure

Emission-line-selected galaxies atz= 0.6–2 in GOODS South: Stellar masses, SFRs, and large-scale structure

Frontier Fields: Combining HST, VLT, andSpitzerdata to explore thez~ 8 Universe behind the lensing cluster MACSJ0416.1−2403

ARE ULTRA-FAINT GALAXIES ATz= 6–8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS

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