Evidence for a Hard Ionizing Spectrum from a z = 6.11 Stellar Population

Mainali, Ramesh; Kollmeier, Juna A.; Stark, Daniel P.; Simcoe, Robert A.; Walth, Gregory; Newman, Andrew B.; Miller, Daniel R.

doi:10.3847/2041-8213/836/1/l14

Cited by 133 publications

(258 citation statements)

References 49 publications

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“…The detection of nebular high-ionization emission lines has underscored the considerable contribution of hot and massive stars to the transparency of the medium in low-luminosity (L L*  ) systems (Vanzella et al 2016a), as expected in scenarios in which stellar winds and supernova explosions blow cavities in the interstellar medium (e.g., Jaskot & Oey 2013;Micheva et al 2017). In fact, the rest-frame ultraviolet and optical line ratios observed in z 0  , z 2 3 = -and z 6 > galaxies suggest a possible evolution of the ionizing radiation field, such that the presence of hot stars seems more common at high redshift, with blackbody mean effective temperatures on the order of 50.000-60.000 K at z 2 3 = - (Fosbury et al 2003;Steidel et al 2014;Holden et al 2016), or even hotter at z 6 > (Stark et al 2015;Mainali et al 2016).…”

Section: Introductionmentioning

confidence: 98%

Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological Distances*

Vanzella

Castellano

Meneghetti

et al. 2017

ApJ

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Magnifying the Early Episodes of Star FormationVanzella, E.; Castellano, M.; Meneghetti, M.; Mercurio, A.; Caminha, G. B.; Cupani, G.; Calura, F.; Christensen, L.; Merlin, E.; Rosati, P. IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document VersionPublisher's PDF, also known as Version of record Publication date: 2017Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Vanzella, E., Castellano, M., Meneghetti, M., Mercurio, A., Caminha, G. B., Cupani, G., ... Tozzi, P. (2017 AbstractWe study the spectrophotometric properties of a highly magnified ( 40 70 m  -) pair of stellar systems identified at z=3.2222 behind the Hubble Frontier Field galaxy cluster MACSJ0416. Five multiple images (out of six) have been spectroscopically confirmed by means of VLT/MUSE and VLT/X-Shooter observations. Each image includes two faint (m 30.6 UV  ), young ( 100  Myr), low-mass ( 10 7 < M  ), low-metallicity (12+Log(O/H);7.7, or 1/10 solar), and compact (30 pc effective radius) stellar systems separated by 300  pc after correcting for lensing amplification. We measured several rest-frame ultraviolet and optical narrow ( 25 v  s kms −1 ) high-ionization lines. These features may be the signature of very hot (T 50,000 > K) stars within dense stellar clusters, whose dynamical mass is likely dominated by the stellar component. Remarkably, the ultraviolet metal lines are not accompanied by Lyα emission (e.g., C IV/Lyα 15 > ), despite the fact that the Lyα line flux is expected to be 150 times brighter (inferred from the Hβ flux). A spatially offset, strongly magnified ( 50 m > ) Lyα emission with a spatial extent 7.6  kpc 2 is instead identified 2kpc away from the system. The origin of such a faint emission could be the result of fluorescent Lyα induced by a transverse leakage of ionizing radiation emerging from the stellar systems and/or may be associated with an underlying and barely detected object (with m 34 UV > de-lensed). This is the first confirmed metal-line emitter at such low-luminosity and redshift without Lyα emission-suggesting that, at least in some cases, a non-uniform covering factor of the neutral gas might hamper the Lyα detection.

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Section: Introductionmentioning

confidence: 98%

Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological Distances*

Vanzella

Castellano

Meneghetti

et al. 2017

ApJ

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“…We will specifically address the first question in a companion paper, but in this study, we start by comparing galaxy and AGN emission in the UV, and we specifically focus on two energies, 54.4 eV and 47.9 eV (228 and 258 Å). Photons with these energies or higher are required to produce the He II and C IV lines that are now observed in high-z galaxy spectra (Stark et al 2015a(Stark et al , 2015bMainali et al 2017). In Figure 10 we calculate the median of the ratio of the monochromatic luminosity produced by the AGN and produced by the galaxy stellar population as a function of the BH mass.…”

Section: Galaxy Versus Agn: Uv Radiation Powering Emission Linesmentioning

confidence: 99%

“…In particular, Mainali et al (2017) showed that UV line ratios can be used to distinguish between AGNs and massive hot metal-poor stars as a powering mechanism using dedicated emission line models (Feltre et al 2016). Mainali et al (2017) argued that based on the presence of C IV and lack of He II, this source was likely to have a break in the ionizing spectrum between 47.9 and 54.4 eV, consistent with a stellar ionizing spectrum and inconsistent with an AGN power-law spectrum. The fact that they detect strong O III] provided further evidence in favor of metal-poor hot stars, as an AGN spectrum would likely have weaker O III] given that oxygen is triply ionized.…”

Section: Introductionmentioning

confidence: 99%

“…Stark et al (2015b) revealed the detection of C IV in 1 of 11 known Lyα emitters at z 7 > , while Sobral et al (2015) and Bowler et al (2017) discuss the detection of He II and O III] in a bright Lyα emitter at z=6.6. Mainali et al (2017) revealed C IV in a gravitationally lensed Lyα emitter at z 6 . In particular, Mainali et al (2017) showed that UV line ratios can be used to distinguish between AGNs and massive hot metal-poor stars as a powering mechanism using dedicated emission line models (Feltre et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Mainali et al (2017) revealed C IV in a gravitationally lensed Lyα emitter at z 6 . In particular, Mainali et al (2017) showed that UV line ratios can be used to distinguish between AGNs and massive hot metal-poor stars as a powering mechanism using dedicated emission line models (Feltre et al 2016). Mainali et al (2017) argued that based on the presence of C IV and lack of He II, this source was likely to have a break in the ionizing spectrum between 47.9 and 54.4 eV, consistent with a stellar ionizing spectrum and inconsistent with an AGN power-law spectrum.…”

Section: Introductionmentioning

confidence: 99%

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High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays

Volonteri

Reines

Atek

et al. 2017

ApJ

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The first billion years of the Universe has been a pivotal time: stars, black holes (BHs), and galaxies formed and assembled, sowing the seeds of galaxies as we know them today. Detecting, identifying, and understanding the first galaxies and BHs is one of the current observational and theoretical challenges in galaxy formation. In this paper we present a population synthesis model aimed at galaxies, BHs, and active galactic nuclei (AGNs) at high redshift. The model builds a population based on empirical relations. The spectral energy distribution of galaxies is determined by age and metallicity, and that of AGNs by BH mass and accretion rate. We validate the model against observations, and predict properties of galaxies and AGN in other wavelength and/or luminosity ranges, estimating the contamination of stellar populations (normal stars and high-mass X-ray binaries) for AGN searches from the infrared to X-rays, and vice versa for galaxy searches. For high-redshift galaxies with stellar ages 1 Gyr < , we find that disentangling stellar and AGN emission is challenging at restframe UV/optical wavelengths, while high-mass X-ray binaries become more important sources of confusion in X-rays. We propose a color-color selection in the James Webb Space Telescope bands to separate AGN versus star-dominated galaxies in photometric observations. We also estimate the AGN contribution, with respect to massive, hot, and metal-poor stars, at driving high-ionization lines, such as C IV and He II. Finally, we test the influence of the minimum BH mass and occupation fraction of BHs in low-mass galaxies on the restframe UV/near-IR and X-ray AGN luminosity function.

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Probing the high-redshift universe with SPICA: Toward the epoch of reionisation and beyond

Egami

Gallerani

Schneider

et al. 2018

Publ. Astron. Soc. Aust.

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With the recent discovery of a dozen dusty star-forming galaxies and around 30 quasars at z > 5 that are hyper-luminous in the infrared (µ L IR > 10 13 L , where µ is a lensing magnification factor), the possibility has opened up for SPICA, the proposed ESA M5 mid-/far-infrared mission, to extend its spectroscopic studies toward the epoch of reionization and beyond. In this paper, we examine the feasibility and scientific potential of such observations with SPICA's far-infrared spectrometer SAFARI, which will probe a spectral range (35-230 µm) that will be unexplored by ALMA and JWST. Our simulations show that SAFARI is capable of delivering good-quality spectra for hyper-luminous infrared galaxies (HyLIRGs) at z = 5-10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate a host of key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the properties of the molecular gas. From a broader perspective, SAFARI offers the potential to open up a new frontier in the study of the early Universe, providing access to uniquely powerful spectral features for probing first-generation objects, such as the key cooling lines of low-metallicity or metal-free forming galaxies (fine-structure and H2 lines) and emission features of solid compounds freshly synthesized by Population III supernovae. Ultimately, SAFARI's ability to explore the high-redshift Universe will be determined by the availability of sufficiently bright targets (whether intrinsically luminous or gravitationally lensed). With its launch expected around 2030, SPICA is ideally positioned to take full advantage of upcoming wide-field surveys such as LSST, SKA, Euclid, and WFIRST, which are likely to provide extraordinary targets for SAFARI.1 Some other SPICA papers refer to this POL field of view as 80 ×80 , but it is 160 ×160 according to the latest design.

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Evidence for a Hard Ionizing Spectrum from a z = 6.11 Stellar Population

Cited by 133 publications

References 49 publications

Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological Distances*

Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological Distances*

High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays

Probing the high-redshift universe with SPICA: Toward the epoch of reionisation and beyond

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