AN INTENSELY STAR-FORMING GALAXY AT z ∼ 7 WITH LOW DUST AND METAL CONTENT REVEALED BY DEEP ALMA AND HST OBSERVATIONS

By Masami Ouchi, Richard S. Ellis, Yoshiaki Ono, K. Nakanishi, K. Kohno, R. Momose, Y. Kurono, M. Ashby, K. Shimasaku, S. Willner and 3 more. 2013

150 citations recorded by the source corpus.

We report deep ALMA observations complemented by associated Hubble Space Telescope (HST) imaging for a luminous (mUV = 25) galaxy, “Himiko,” at a redshift of z = 6.595. The galaxy is remarkable for its high star formation rate, 100 M☉ yr−1, which has been securely estimated from our deep HST and Spitzer photometry, and the absence of any evidence for strong active galactic nucleus activity or gravitational lensing magnification. Our ALMA observations probe an order of magnitude deeper than previous IRAM observations, yet fail to detect a 1.2 mm dust continuum, indicating a flux of <52 μJy, which is comparable to or weaker than that of local dwarf irregulars with much lower star formation rates. We likewise provide a strong upper limit for the flux of [C ii] 158 μm, , which is a diagnostic of the hot interstellar gas that is often described as a valuable probe for early galaxies. In fact, our observations indicate that Himiko lies off the local –star formation rate scaling relation by a factor of more than 30. Both aspects of our ALMA observations suggest that Himiko is a unique object with a very low dust content and perhaps nearly primordial interstellar gas. Our HST images provide unique insight into the morphology of this remarkable source, highlighting an extremely blue core of activity and two less extreme associated clumps. Himiko is undergoing a triple major merger event whose extensive ionized nebula of Lyα emitting gas, discovered in our earlier work with Subaru, is powered by star formation and the dense circumgalactic gas. We are likely witnessing an early massive galaxy during a key period of its mass assembly close to the end of the reionization era.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/dc359c4852515590177ae7b30671e5622e736793

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Citations in the corpus

Dusty Star Forming Galaxies at High Redshift (2014, methodology): “Similarly, Ouchi et al. (2013) utilized ALMA to search for [CII] from Himiko, a luminous galaxy at z ∼ 6.5 that forms stars at ∼100 M⊙ yr−1.”
ALMA IMAGING OF GAS AND DUST IN A GALAXY PROTOCLUSTER AT REDSHIFT 5.3: [C ii] EMISSION IN “TYPICAL” GALAXIES AND DUSTY STARBURSTS ≈1 BILLION YEARS AFTER THE BIG BANG (2014, background): “Recent searches for [CII] emission in z>6.5 Lyman-α emitters (LAEs) and Lyman-α blobs (LABs) have been unsuccessful, even with ALMA (e.g., Walter et al. 2012b; Ouchi et al. 2013; GonzalezLopez et al. 2014).”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, methodology): “However, what is already clear is that MASOSA provides a new example of a relatively compact Lyα emitter with a similar luminosity to Himiko (Ouchi et al. 2009, 2013), but with a much more extreme EW, revealing that such high luminosity sources present diverse properties and may have a diverse natur”
ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS (2016, background): “…first results from these facilities indicated that there was no detectable dustenshrouded star formation in normal or even extremely bright UV -selected z > 5 galaxies (Walter et al. 2012; Ouchi et al. 2013; Ota et al. 2014; González-López et al. 2014; Riechers et al. 2014; Maiolino et al. 2015).”
A deep ALMA image of the Hubble Ultra Deep Field (2016, background): “Most early ALMA programmes have focused (sensibly) on pointed observations of known objects (e.g. Hodge et al. 2013; Karim et al. 2013; Ouchi et al. 2013; Bussmann et al. 2015; Capak et al. 2015; Maiolino et al. 2015; Simpson et al. 2015a, 2015b; Scoville et al. 2016), including gravitationally…”
Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA (2018, methodology): “In addition, the sample includes objects with deep 3σ upper limits on the IRX obtained with ALMA: Himiko (Ouchi et al. 2013; Schaerer et al. 2015), IOK-1 (Ota et al. 2014; Schaerer et al. 2015), SXDF-NB1006-2 (Inoue et al. 2016), COS-301855981, COS-29870300247 (Smit et al. 2018), and MACS1149-JD1 (H”
The bright end of the galaxy luminosity function at z≃7: before the onset of mass quenching? (2013, methodology): “Although an extreme galaxy, Himiko illustrates the potential for detailed study of rare and bright z ' 7 galaxies that can only be efficiently detected in ground-based narrow- or broad-band survey fields.”
GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4 (2014, background): “This effect, which seems to nicely fit andexplain some recent observations of metallicity and gas masses at high redshift (see, e.g., Ouchi et al. 2013; Tan et al. 2013; Troncoso et al. 2014), should be carefully taken into account when dealing with high redshift sources and deriving more general…”
Lyα EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION (2015, background): “The second question is whether these rarer luminous sources (c.f. Matthee et al. 2015; Ouchi et al. 2013) are physically distinct from the fainter population.”
SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “A number of observational and theoretical studies have aimed to uncover the physical origins of these bright LAEs (e.g., Ouchi et al. 2013 and Zabl et al. 2015 for Himiko; Bowler et al. 2017b, Pacucci et al. 2017, and Shibuya et al. 2017b for CR7).”
The assembly of ‘normal’ galaxies at z ∼ 7 probed by ALMA (2015, background): “Low metallicity of high-z galaxies has been a possible interpretation for the lack of [CII] detection in some star forming galaxies at z∼6.5 (Ouchi et al. 2013; Vallini et al. 2013).”
The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “…with high EW: these galaxies will contain less dust (as ALMA and Plateau de Bure Interferometer (PdBI) re- sults are suggesting, Walter et al. 2012; Ouchi et al. 2013; Ota et al. 2014; Schaerer et al. 2015; Maiolino et al. 2015; Capak et al. 2015; Bouwens et al. 2016b; Pentericci et al. 2016)…”
Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ∼2000 Lyα emitters at z = 6–7 over the 0.3–0.5 Gpc2 survey area (2017, background): “Because LAEs are low stellar mass galaxies with strong Lyα indicative of a starburst with young massive stars producing a large amount of ionizing photons (Ouchi et al. 2013; Sobral et al. 2015; Stark et al. 2015), LAEs are used as probes of young galaxies.”