CR7 is the brightest z = 6.6 Ly ... emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation ...using cosmological hydrodynamical simulations. Several simulated galaxies show the same 'Pop III wave' pattern observed in CR7. However, to reproduce the extreme CR7 Ly.../He ii1640 line luminosities ($L_...\rm \alpha /He\,\small ...II...$) a top-heavy initial mass function and a massive ( ... 10... M...) Pop III burst with age ... 2 Myr are required. Assuming that the observed properties of Ly ... and He ii emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with L... > 10... erg s... should also host Pop III stars producing an observable $L_...\rm He\,\small ...II...\gtrsim 10 greater than or equal to ..42.7...\,...\rm erg...\,...\rm s... greater than or equal to ..-1...$. As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts L..., $L_...\rm He\,\small ...II...$, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios. (ProQuest: ... denotes formulae/symbols omitted.)
CR7 is the brightest z = 6.6 Ly ... emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation ...using cosmological hydrodynamical simulations. Several simulated galaxies show the same 'Pop III wave' pattern observed in CR7. However, to reproduce the extreme CR7 Ly.../He ii1640 line luminosities ($L_...\rm \alpha /He\,\small ...II...$) a top-heavy initial mass function and a massive ( ... 10... M...) Pop III burst with age ... 2 Myr are required. Assuming that the observed properties of Ly ... and He ii emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with L... > 10... erg s... should also host Pop III stars producing an observable $L_...\rm He\,\small ...II...\gtrsim 10^...42.7...\,...\rm erg...\,...\rm s...^...-1...$. As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts L..., $L_...\rm He\,\small ...II...$, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios. (ProQuest: ... denotes formulae/symbols omitted.)
The ultraviolet continuum traces young stars while the near-infrared unveils older stellar populations and dust-obscured regions. Balmer emission lines provide insights on gas properties and young ...stellar objects but are highly affected by dust attenuation. The near-infrared Paschen lines suffer less dust attenuation and can be used to measure star formation rates (SFRs) in star-forming regions obscured by dust clouds. We select 13 sources between redshifts 1 and 3 observed with HST, JWST/NIRCam and NIRSpec based on the availability of at least one Balmer and one Paschen line with S/N > 5. With a newly-developed version of CIGALE, we fit their hydrogen line equivalent widths (EWs) and photometric data. We assess the impacts of the removal of spectroscopic data by comparing the quality of the fits of the spectro-photometric data to those with photometric data only. We compare the single (BC03) vs binary (BPASS) stellar populations models in the fitting process of spectro-photometric data. We derive the differential attenuation and explore different attenuation recipes by fitting spectro-photometric data with BC03. For each stellar model and for each input dataset (with and without EWs), we quantify the deviation on the SFRs and stellar masses from the "standard" choice. On average, the SFRs are overestimated and the stellar masses are underestimated when EWs are not included as input data. We find a major contribution of the H\({\alpha}\) emission line to the broadband photometric measurements of our sources, and a trend of increasing contribution with specific SFR. Using the BPASS models has a significant impact on the derived SFRs and stellar masses. We show that a flexible attenuation recipe provides more accurate estimates of the dust attenuation parameters, especially the differential attenuation which agrees with the original value of Charlot & Fall (2000).
The galaxy integrated star-formation rate (SFR) surface density (\(\Sigma_{\rm SFR}\)) has been proposed as a valuable diagnostic of the mass accumulation in galaxies as being more tightly related to ...the physics of star-formation (SF) and stellar feedback than other SF indicators. In this paper, we assemble a statistical sample of 230 galaxies observed with JWST in the GLASS and CEERS spectroscopic surveys to estimate Balmer line based dust attenuations and SFRs, and UV rest-frame effective radii. We study the evolution of galaxy SFR and \(\Sigma_{\rm SFR}\) in the first 1.5 Billion years of our Universe, finding that \(\Sigma_{\rm SFR}\) is mildly increasing with redshift with a linear slope of \(0.16 \pm 0.06\). We also explore the dependence of SFR and \(\Sigma_{\rm SFR}\) on stellar mass, showing that a SF 'Main-Sequence' and a \(\Sigma_{\rm SFR}\) `Main-Sequence' are in place out to z=10, with a similar slope compared to the same relations at lower redshifts. We find that the specific SFR (sSFR) and \(\Sigma_{\rm SFR}\) are correlated with the OIII5007/OII3727 ratio and with indirect estimates of the escape fraction of Lyman continuum photons, hence they likely play an important role in the evolution of ionization conditions and in the escape of ionizing radiation. We also search for spectral outflow signatures in a subset of galaxies observed at high resolution, finding an outflow incidence of \(2/11\) (\(=20\%^{32\%}_{9\%}\)) at \(z<6\), but no evidence at \(z>6\) (\(<26\%\)). Finally, we find a positive correlation between A\(_V\) and \(\Sigma_{\rm SFR}\), and a flat trend as a function of sSFR, indicating that there is no evidence of a drop of A\(_V\) in extremely star-forming galaxies between z=4 and 10. This might be at odds with a dust-clearing outflow scenario, which might instead take place at redshifts \(z\geq 10\), as suggested by some theoretical models.
ASTRO2020 A major scientific goal of JWST is to probe the epoch of re-ionization of the
Universe at z above 6, and up to 20 and beyond. At these redshifts, galaxies
are just beginning to form and the ...observable objects are early black holes,
supernovae, and cosmic infrared background. The JWST has the necessary
sensitivity to observe these targets individually, but a public deep and wide
science enabling survey in the wavelength range from 2-5 $\mu$m is needed to
discover these black holes and supernovae and to cover the area large enough
for cosmic infrared background to be reliably studied. This enabling survey
will also discover a large number of other transients and enable sciences such
as supernova cosmology up to z $\sim$ 5, star formation history at high
redshift through supernova explosions, faint stellar objects in the Milky Way,
and galaxy evolution up to z approaching 10. The results of this survey will
also serve as an invaluable target feeder for the upcoming era of ELT and SKA.
CR7 is the brightest $z=6.6 \, {\rm Ly}\alpha$ emitter (LAE) known to date,
and spectroscopic follow-up by Sobral et al. (2015) suggests that CR7 might
host Population (Pop) III stars. We examine ...this interpretation using
cosmological hydrodynamical simulations. Several simulated galaxies show the
same "Pop III wave" pattern observed in CR7. However, to reproduce the extreme
CR7 ${\rm Ly}\alpha$/HeII1640 line luminosities ($L_{\rm \alpha/He II}$) a
top-heavy IMF and a massive ($>10^{7}{\rm M}_{\odot}$) PopIII burst with age
$<2$ Myr are required. Assuming that the observed properties of ${\rm
Ly}\alpha$ and HeII emission are typical for Pop III, we predict that in the
COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at $z=6.6$ with $L_{\alpha}
>10^{43.3}{\rm erg}\,{\rm s}^{-1}$ should also host Pop III stars producing an
observable $L_{\rm He II}>10^{42.7}{\rm erg}\,{\rm s}^{-1}$. As an alternate
explanation, we explore the possibility that CR7 is instead powered by
accretion onto a Direct Collapse Black Hole (DCBH). Our model predicts
$L_{\alpha}$, $L_{\rm He II}$, and X-ray luminosities that are in agreement
with the observations. In any case, the observed properties of CR7 indicate
that this galaxy is most likely powered by sources formed from pristine gas. We
propose that further X-ray observations can distinguish between the two above
scenarios.
JWST was conceived and built to answer one of the most fundamental questions that humans can address empirically: "How did the Universe make its first stars?". Our First Lights At REionization ...(FLARE) project transforms the quest for the epoch of reionization from the static to the time domain. It targets the complementary question: "What happened to those first stars?". It will be answered by observations of the most luminous events: supernovae and accretion on to black holes formed by direct collapse from the primordial gas clouds. These transients provide direct constraints on star-formation rates (SFRs) and the truly initial Initial Mass Function (IMF), and they may identify possible stellar seeds of supermassive black holes (SMBHs). Furthermore, our knowledge of the physics of these events at ultra-low metallicity will be much expanded. JWST's unique capabilities will detect these most luminous and earliest cosmic messengers easily in fairly shallow observations. However, these events are very rare at the dawn of cosmic structure formation and so require large area coverage. Time domain astronomy can be advanced to an unprecedented depth by means of a shallow field of JWST reaching 27 mag AB in 2 and 4.4 microns over a field as large as 0.1 square degree visited multiple times each year. Such a survey may set strong constraints or detect massive Pop III SNe at redshifts beyond 10, pinpointing the redshift of the first stars, or at least their death. Based on our current knowledge of superluminous supernovae (SLSNe), such a survey will find one or more SLSNe at redshifts above 6 in five years and possibly several direct collapse black holes. Although JWST is not designed as a wide field survey telescope, we show that such a wide field survey is possible with JWST and is critical in addressing several of its key scientific goals.
A major scientific goal of JWST is to probe the epoch of re-ionization of the Universe at z above 6, and up to 20 and beyond. At these redshifts, galaxies are just beginning to form and the ...observable objects are early black holes, supernovae, and cosmic infrared background. The JWST has the necessary sensitivity to observe these targets individually, but a public deep and wide science enabling survey in the wavelength range from 2-5 \(\mu\)m is needed to discover these black holes and supernovae and to cover the area large enough for cosmic infrared background to be reliably studied. This enabling survey will also discover a large number of other transients and enable sciences such as supernova cosmology up to z \(\sim\) 5, star formation history at high redshift through supernova explosions, faint stellar objects in the Milky Way, and galaxy evolution up to z approaching 10. The results of this survey will also serve as an invaluable target feeder for the upcoming era of ELT and SKA.
CR7 is the brightest \(z=6.6 \, {\rm Ly}\alpha\) emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. (2015) suggests that CR7 might host Population (Pop) III stars. We examine ...this interpretation using cosmological hydrodynamical simulations. Several simulated galaxies show the same "Pop III wave" pattern observed in CR7. However, to reproduce the extreme CR7 \({\rm Ly}\alpha\)/HeII1640 line luminosities (\(L_{\rm \alpha/He II}\)) a top-heavy IMF and a massive (\(>10^{7}{\rm M}_{\odot}\)) PopIII burst with age \(<2\) Myr are required. Assuming that the observed properties of \({\rm Ly}\alpha\) and HeII emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at \(z=6.6\) with \(L_{\alpha} >10^{43.3}{\rm erg}\,{\rm s}^{-1}\) should also host Pop III stars producing an observable \(L_{\rm He II}>10^{42.7}{\rm erg}\,{\rm s}^{-1}\). As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion onto a Direct Collapse Black Hole (DCBH). Our model predicts \(L_{\alpha}\), \(L_{\rm He II}\), and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios.
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