Early Low-mass Galaxies and Star-cluster Candidates at z ∼ 6–9 Identified by the Gravitational-lensing Technique and Deep Optical/Near-infrared Imaging

Kikuchihara, Shotaro; Ouchi, Masami; Ono, Yoshiyasu; Mawatari, Ken; Chevallard, Jacopo; Harikane, Yuichi; Kojima, Takashi; Oguri, Masamune; Bruzual, G.; Charlot, S.

doi:10.3847/1538-4357/ab7dbe

Cited by 80 publications

(113 citation statements)

References 78 publications

(84 reference statements)

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“…• Dust: We tested the impact of dust attenuation on the results by allowing a wider range of dust attenuation optical depths in the V-band, τ𝑉 , compared to that allowed in the reference model (up to τ𝑉 = 3 or 𝐴 𝑉 = 3.25). This is similar to the range allowed in Song et al (2016); Bhatawdekar et al (2019); Kikuchihara et al (2020). Recent results have also indicated that a steeper dust attenuation law than the Calzetti law potentially fits better the SEDs of high-redshift galaxies (Capak et al 2015;Reddy et al 2015Reddy et al , 2018a.…”

Section: Sed-fitting Assumptionssupporting

confidence: 77%

“…Indeed, using the full HFF dataset to detect gravitationally magnified 𝑧 6 objects led to the discovery of the faintest high-redshift galaxies and extended their UV luminosity functions down to 𝑀 𝑈 𝑉 −13 AB (Livermore et al 2017;Bouwens et al 2017;Ishigaki et al 2018;Atek et al 2018). More recently, the first measurements of 𝑧 6 GSMFs using HFF HST and Spitzer data have extended the low-mass end of the high-redshift GSMF down to 𝑀 ★ > 10 6 M , confirming the steep low-mass end slopes found in blank field studies (Bhatawdekar et al 2019;Kikuchihara et al 2020).…”

Section: Introductionsupporting

confidence: 61%

“…Finally, in Fig. 5, we compare our 𝑀 ★ − 𝑀 𝑈 𝑉 -relations to the most recent results in the literature, namely Song et al (2016), Bhatawdekar et al (2019), andKikuchihara et al (2020). Our reference BEAGLE configuration has a similar relation to Bhatawdekar et al (2019) with slightly higher masses.…”

Section: Mass-luminosity Scaling Relationmentioning

confidence: 54%

“…This approach is commonly used in the study of high-redshift GSMFs because selection and completeness effects are well-studied for UV luminosity functions (e.g. González et al 2011;Song et al 2016;Kikuchihara et al 2020).…”

Section: High-redshift Galaxy Stellar Mass Functionsmentioning

confidence: 99%

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How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

Furtak

Atek

Lehnert

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer/IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to $M_{\star }\gt 10^{6}\, \text{M}_{\odot}$ and we find the z ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope $\alpha \simeq -1.96_{-0.08}^{+0.09}$ and a turnover at $\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$ with a curvature of $\beta \simeq 1.00_{-0.73}^{+0.87}$ for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV ≤ 0.2. We find that the z ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from $\alpha \simeq -1.82_{-0.07}^{+0.08}$ for an exponentially rising SFH to $\alpha \simeq -2.34_{-0.10}^{+0.11}$ when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF.

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Section: Sed-fitting Assumptionssupporting

confidence: 77%

Section: Introductionsupporting

confidence: 61%

Section: Mass-luminosity Scaling Relationmentioning

confidence: 54%

Section: High-redshift Galaxy Stellar Mass Functionsmentioning

confidence: 99%

See 2 more Smart Citations

How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

Furtak

Atek

Lehnert

et al. 2020

Monthly Notices of the Royal Astronomical Society

Self Cite

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“…Robertson et al 2015). As a consequence, it is popular to appeal to contributions from a larger number of sub-luminous sources, which can only be partially probed via current deep surveys (e.g., Bouwens et al 2015, Livermore et al 2017, Bhatawdekar et al 2019, Kikuchihara et al 2020. With current facilities, the only way to characterise the physical properties of this sub-luminous population is to use the magnification afforded by gravitational lensing (for a review see Kneib & Natarajan 2011).…”

Section: Introductionmentioning

confidence: 99%

ALMA Lensing Cluster Survey: a strongly lensed multiply imaged dusty system at z ≥ 6

Laporte

Zitrin

Ellis

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift z =6.07 viewed through the cluster MACSJ0600.1-2008 (z=0.46). A ≃ 4σ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large program, and the redshift is secured via [C II] 158 μm emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy’s spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification μ ≳30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionisation. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of $\rm {2.9^{+11.5}_{-2.3}\times 10^9}$ and $\rm {4.8^{+4.5}_{-3.4}\times 10^6}$ $\rm {M_{\odot }}$ respectively, a star formation rate of $\rm {9.7^{+22.0}_{-6.6} M_{\odot } yr^{-1}}$, an intrinsic size of $\rm {0.54^{+0.26}_{-0.14}}$ kpc, and a luminosity-weighted age of 200±100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation.

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The First Billion Years project: Finding infant globular clusters at z = 6

Phipps

Khochfar

Varri

et al. 2020

A&A

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Aims. We aim to conduct an assessment of the demographics of substructures in cosmological simulations to identify low-mass stellar systems at high redshift, with a particular focus on globular cluster (GC) candidates. Methods. We explored a suite of high-resolution cosmological simulations from the First Billion Years Project (FiBY) at z ≥ 6. All substructures within the simulations have been identified with the SUBFIND algorithm. From our analysis, two distinct groups of objects emerge. We hypothesise that the substructures in the first group, which appear to have a high baryon fraction (fb ≥ 0.95), are possible infant GC candidates. Objects belonging to the second group have a high stellar fraction (f* ≥ 0.95) and show a potential resemblance to infant ultra-faint dwarf galaxies. Results. The high baryon fraction objects identified in this study are characterised by a stellar content similar to the one observed in present-day GCs, but they still contain a high gas fraction (fgas ∼ 0.95) and a relatively low amount of dark matter. They are compact systems, with densities higher than the average population of FiBY systems at the same stellar mass. Their sizes are consistent with recent estimates based on the first observations of possible proto-GCs at high redshifts. These types of infant GC candidates appear to be more massive and more abundant in massive host galaxies, indicating that the assembly of galaxies via mergers may play an important role in building several GC-host scaling relations. Specifically, we express the relation between the mass of the most massive infant GC and its host stellar mass as log(Mcl) = (0.31 ± 0.15) log (M*, gal + (4.17 ± 1.06). We also report a new relation between the most massive infant GC and the parent specific star formation rate of the form log(Mcl) = (0.85 ± 0.30) log (sSFR)+α that describes the data at both low and high redshift. Finally, we assess the present-day GC mass (GC number) – halo mass relation offers a satisfactory description of the behaviour of our infant GC candidates at high redshift, suggesting that such a relation may be set at formation.

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Early Low-mass Galaxies and Star-cluster Candidates at z ∼ 6–9 Identified by the Gravitational-lensing Technique and Deep Optical/Near-infrared Imaging

Cited by 80 publications

References 78 publications

How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

ALMA Lensing Cluster Survey: a strongly lensed multiply imaged dusty system at z ≥ 6

The First Billion Years project: Finding infant globular clusters at z = 6

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