scholarly journals Rest-frame UV spectroscopy of extreme [OIII] emitters at 1.3 < z < 3.7: Toward a high-redshift UV reference sample for JWST

2020 ◽  
Author(s):  
Mengtao Tang ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot ◽  
Ryan Endsley ◽  
...  
Keyword(s):  
Rest Frame ◽  
Uv Spectroscopy ◽  
High Redshift ◽  
Reference Sample ◽  
Line Emission ◽  
Uv Emission ◽  
Consistent Picture ◽  
Low Metallicity ◽  
Extreme Sensitivity ◽  
Galaxy Population

Abstract Deep spectroscopy of galaxies in the reionization era has revealed intense C III] and C IV line emission (EW &gt;15 − 20 Å). In order to interpret the nebular emission emerging at z &gt; 6, we have begun targeting rest-frame UV emission lines in galaxies with large specific star formation rates (sSFRs) at 1.3 &lt; z &lt; 3.7. We find that C III] reaches the EWs seen at z &gt; 6 only in large sSFR galaxies with [O III]+Hβ EW &gt;1500 Å. In contrast to previous studies, we find that many galaxies with intense [O III] have weak C III] emission (EW =5 − 8 Å), suggesting that the radiation field associated with young stellar populations is not sufficient to power strong C III]. Photoionization models demonstrate that the spread in C III] among systems with large sSFRs ([O III]+Hβ EW &gt;1500 Å) is driven by variations in metallicity, a result of the extreme sensitivity of C III] to electron temperature. We find that the strong C III] emission seen at z &gt; 6 (EW &gt;15 Å) requires metal poor gas (≃ 0.1 Z⊙) whereas the weaker C III] emission in our sample tends to be found at moderate metallicities (≃ 0.3 Z⊙). The luminosity distribution of the C III] emitters in our z ≃ 1 − 3 sample presents a consistent picture, with stronger emission generally linked to low luminosity systems (MUV &gt; −19.5) where low metallicities are more likely. We quantify the fraction of strong C III] and C IV emitters at z ≃ 1 − 3, providing a baseline for comparison against z &gt; 6 samples. We suggest that the first UV line detections at z &gt; 6 can be explained if a significant fraction of the early galaxy population is found at large sSFR (&gt;200 Gyr−1) and low metallicity (&lt;0.1 Z⊙).

scholarly journals The WISSH quasars project

2020 ◽  
Vol 635 ◽  
pp. A157 ◽  
Author(s):  
A. Travascio ◽  
L. Zappacosta ◽  
S. Cantalupo ◽  
E. Piconcelli ◽  
F. Arrigoni Battaia ◽  
...  
Keyword(s):  
Average Velocity ◽  
Rest Frame ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Emission Lines ◽  
Host Galaxy ◽  
Uv Emission ◽  
Broad Emission ◽  
Highly Sensitive ◽  
Integral Field

Context. In recent years, Lyα nebulae have been routinely detected around high redshift, radio-quiet quasars thanks to the advent of the highly sensitive integral field spectrographs. Constraining the physical properties of the Lyα nebulae is crucial for a full understanding of the circum-galactic medium (CGM). The CGM acts both as a repository for intergalactic and galactic baryons as well as a venue of feeding and feedback processes. The most luminous quasars are privileged test-beds to study these processes, given their large ionising fluxes and dense CGM environments in which they are expected to be embedded. Aims. We aim to characterise the rest-frame ultraviolet (UV) emission lines in the CGM around a hyper-luminous, broad emission line, radio-quiet quasar at z ∼ 3.6, which exhibits powerful outflows at both nuclear and host galaxy scales. Methods. We analyse VLT/MUSE observations of the quasar J1538+08 (Lbol = 6 × 1047 erg s−1), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content. Results. We report the discovery of a very luminous (∼2 × 1044 erg s−1), giant Lyα nebula and a likely associated extended (75 kpc) CIV nebula. The Lyα nebula emission exhibits moderate blueshift (∼440 km s−1) compared to the quasar systemic redshift and a large average velocity dispersion (σ¯v ∼ 700 km s−1) across the nebula, while the CIV nebula shows average velocity dispersion of σ¯v ∼ 350 km s−1. The Lyα line profile exhibits a significant asymmetry towards negative velocity values at 20−30 kpc south of the quasar and is well parametrised by the following two Gaussian components: a narrow (σ ∼ 470 km s−1) systemic one plus a broad (σ ∼ 1200 km s−1), blueshifted (∼1500 km s−1) one. Conclusions. Our analysis of the MUSE observation of J1538+08 reveals metal-enriched CGM around this hyper-luminous quasar. Furthermore, our detection of blueshifted emission in the emission profile of the Lyα nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs.

scholarly journals A search for dust and molecular gas in enormous Lyα nebulae at z ≈ 2

2020 ◽  
Vol 645 ◽  
pp. L3
Author(s):  
Roberto Decarli ◽  
Fabrizio Arrigoni-Battaia ◽  
Joseph F. Hennawi ◽  
Fabian Walter ◽  
Jason X. Prochaska ◽  
...  
Keyword(s):  
Rest Frame ◽  
High Redshift ◽  
Cluster Formation ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Molecular Gas ◽  
Gas Reservoirs ◽  
Time Investment ◽  
Significant Step ◽  
Radio Power

Enormous Lyα nebulae, extending over 300−500 kpc around quasars, represent the pinnacle of galaxy and cluster formation. Here we present IRAM Plateau de Bure Interferometer observations of the enormous Lyα nebulae “Slug” (z = 2.282) and “Jackpot” (z = 2.041). Our data reveal bright, synchrotron emission associated with the two radio-loud active galactic nuclei embedded in the targeted nebulae as well as molecular gas, as traced via the CO(3−2) line, in three galaxies (two sources in Slug, and one in Jackpot). All of the CO emission is associated with galaxies detected in their rest-frame UV stellar emission. The total mass in molecular gas of these three galaxies [∼(3 − 5) × 1010 M⊙] is comparable with the total ionized gas mass responsible for the diffuse nebular emission. Our observations place limits on the molecular gas emission in the nebulae: the molecular gas surface density is ΣH2 <  12 − 25 M⊙ pc−2 for the Slug nebula and ΣH2 <  34 − 68 M⊙ pc−2 for the Jackpot nebula. These are consistent with the expected molecular gas surface densities, as predicted via photoionization models of the rest-frame UV line emission in the nebulae, and via Lyα absorption in the Jackpot nebula. Compared to other radio-loud quasars at z >  1 and high-redshift radio-loud galaxies, we do not find any strong trends relating the molecular gas reservoirs, the radio power, and the Lyα luminosities of these systems. The significant step in sensitivity required to achieve a detection of the molecular gas from the nebulae, if present, will require a substantial time investment with JVLA, NOEMA, or ALMA.

scholarly journals Intense C III] λλ1907,1909 emission from a strong Lyman continuum emitting galaxy

2018 ◽  
Vol 616 ◽  
pp. L14 ◽  
Author(s):  
D. Schaerer ◽  
Y. I. Izotov ◽  
K. Nakajima ◽  
G. Worseck ◽  
J. Chisholm ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Production Efficiency ◽  
Rest Frame ◽  
Stellar Population ◽  
Uv Spectrum ◽  
Star Forming ◽  
Uv Emission ◽  
Lyman Continuum ◽  
Low Metallicity ◽  
Imaging Spectrograph

We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum (LyC) emitter at low redshift – the compact, low-metallicity, star-forming galaxy J1154+2443 – with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Lyα and C III] λ1909 emission, as well as O III] λ1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(C III]) = 11.7 ± 2.9 Å rest-frame), although their equivalent widths should be reduced due to the loss of ionizing photons. The intrinsic ionizing photon production efficiency of J1154+2443 is high, log(ξ0ion = 25.56 erg−1 Hz), comparable to that of other recently discovered z ~ 0.3−0.4 LyC emitters. Combining our measurements and earlier determinations from the literature, we find a trend of increasing ξ0ion with increasing C III] λ1909 equivalent width, which can be understood by a combination of decreasing stellar population age and metallicity. Simple ionization and density-bounded photoionization models can explain the main observational features including the UV spectrum of J1154+2443.

scholarly journals A physical model for [C ii] line emission from galaxies

2019 ◽  
Vol 489 (1) ◽  
pp. 1-12 ◽  
Author(s):  
A Ferrara ◽  
L Vallini ◽  
A Pallottini ◽  
S Gallerani ◽  
S Carniani ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Star Formation Rate ◽  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Emission Lines ◽  
Additional Information ◽  
Low Metallicity ◽  
Local Relation

ABSTRACT A tight relation between the [C ii] 158 $\mu$m line luminosity and star formation rate is measured in local galaxies. At high redshift (z > 5), though, a much larger scatter is observed, with a considerable (15–20 per cent) fraction of the outliers being [C ii]-deficient. Moreover, the [C ii] surface brightness ($\Sigma_{\rm [C\, \small {II}]}$) of these sources is systematically lower than expected from the local relation. To clarify the origin of such [C ii]-deficiency, we have developed an analytical model that fits local [C ii] data and has been validated against radiative transfer simulations performed with cloudy. The model predicts an overall increase of $\Sigma_{\rm [C\, \small {II}]}$ with ΣSFR. However, for ΣSFR ${\gtrsim} 1 \, \mathrm{M}_\odot \,{\rm yr}^{-1}\,{\rm kpc}^{-2}$, $\Sigma_{\rm [C\, \small {II}]}$ saturates. We conclude that underluminous [C ii] systems can result from a combination of three factors: (a) large upward deviations from the Kennicutt–Schmidt relation (κs ≫ 1), parametrized by the ‘burstiness’ parameter κs; (b) low metallicity; (c) low gas density, at least for the most extreme sources (e.g. CR7). Observations of [C ii] emission alone cannot break the degeneracy among the above three parameters; this requires additional information coming from other emission lines (e.g. [O iii]88 $\mu$m, C iii]1909 Å, CO lines). Simple formulae are given to interpret available data for low- and high-z galaxies.

scholarly journals Interpreting the Spitzer/IRAC colours of 7 ≤ z ≤ 9 galaxies: distinguishing between line emission and starlight using ALMA

2020 ◽  
Vol 497 (3) ◽  
pp. 3440-3450 ◽  
Author(s):  
G W Roberts-Borsani ◽  
R S Ellis ◽  
N Laporte
Keyword(s):  
Optical Properties ◽  
Rest Frame ◽  
High Redshift ◽  
Line Emission ◽  
Intense Line ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
History Of ◽  
Dependent Behaviour ◽  
Lower Redshift

ABSTRACT Prior to the launch of JWST, Spitzer/IRAC photometry offers the only means of studying the rest-frame optical properties of z &gt;7 galaxies. Many such high-redshift galaxies display a red [3.6]−[4.5] micron colour, often referred to as the ‘IRAC excess’, which has conventionally been interpreted as arising from intense [O iii]+H β emission within the [4.5] micron bandpass. An appealing aspect of this interpretation is similarly intense line emission seen in star-forming galaxies at lower redshift as well as the redshift-dependent behaviour of the IRAC colours beyond z ∼ 7 modelled as the various nebular lines move through the two bandpasses. In this paper, we demonstrate that, given the photometric uncertainties, established stellar populations with Balmer (4000 Å rest frame) breaks, such as those inferred at z &gt; 9 where line emission does not contaminate the IRAC bands, can equally well explain the redshift-dependent behaviour of the IRAC colours in 7 ≲ z ≲ 9 galaxies. We discuss possible ways of distinguishing between the two hypotheses using ALMA measures of [O iii] λ88 micron and dust continuum fluxes. Prior to further studies with JWST, we show that the distinction is important in determining the assembly history of galaxies in the first 500 Myr.

scholarly journals Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z ~ 2–4 as probed by multi-J CO lines

2017 ◽  
Vol 608 ◽  
pp. A144 ◽  
Author(s):  
C. Yang ◽  
A. Omont ◽  
A. Beelen ◽  
Y. Gao ◽  
P. van der Werf ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Line Emission ◽  
Far Infrared ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Large Area ◽  
Line Energy ◽  
Submillimeter Galaxies ◽  
Dust Mass

We present the IRAM-30 m observations of multiple-J CO (Jup mostly from 3 up to 8) and [C I](3P2 → 3P1) ([C I](2–1) hereafter) line emission in a sample of redshift ~2–4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest-lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Forty-seven CO lines and 7 [C I](2–1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, and hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around Jup ~ 5–7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density nH2 ~ 102.5–104.1 cm-3 and the kinetic temperature Tk  ~ 20–750 K. The gas thermal pressure Pth ranging from~105 K cm-3 to 106 K cm-3 is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with nH2 ~ 102.8–104.6 cm-3 and Tk  ~ 20–30 K, which is less correlated with star formation, and a high-excitation one (nH2 ~ 102.7–104.2 cm-3, Tk  ~ 60–400 K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the Jup ≥ 5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [C I](2–1) lines follow the tight linear correlation between the luminosities of the [C I](2–1) and the CO(1–0) line found in local starbursts, indicating that [C I] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well. The total mass of the molecular gas reservoir, (1–30) × 1010M⊙, derived based on the CO(3–2) fluxes and αCO(1–0) = 0.8 M⊙ ( K km s-1 pc2)-1, suggests a typical molecular gas depletion time tdep ~ 20–100 Myr and a gas to dust mass ratio δGDR ~ 30–100 with ~20%–60% uncertainty for the SMGs. The ratio between CO line luminosity and the dust mass L′CO/Mdust appears to be slowly increasing with redshift for high-redshift SMGs, which need to be further confirmed by a more complete SMG sample at various redshifts. Finally, through comparing the linewidth of CO and H2O lines, we find that they agree well in almost all our SMGs, confirming that the emitting regions of the CO and H2O lines are co-spatially located.

scholarly journals Submillimeter line emission from LMC 30 Doradus: The impact of a starburst on a low-metallicity environment

2012 ◽  
Vol 544 ◽  
pp. A84 ◽  
Author(s):  
J. L. Pineda ◽  
N. Mizuno ◽  
M. Röllig ◽  
J. Stutzki ◽  
C. Kramer ◽  
...  
Keyword(s):  
Line Emission ◽  
Low Metallicity ◽  
The Impact ◽  
30 Doradus

scholarly journals Accurately predicting the escape fraction of ionizing photons using rest-frame ultraviolet absorption lines

2018 ◽  
Vol 616 ◽  
pp. A30 ◽  
Author(s):  
J. Chisholm ◽  
S. Gazagnes ◽  
D. Schaerer ◽  
A. Verhamme ◽  
J. R. Rigby ◽  
...  
Keyword(s):  
Early Universe ◽  
Rest Frame ◽  
High Redshift ◽  
Flux Ratio ◽  
Companion Paper ◽  
Absorption Lines ◽  
Indirect Methods ◽  
High Redshift Galaxies ◽  
Lyman Continuum ◽  
Redshift Galaxies

The fraction of ionizing photons that escape high-redshift galaxies sensitively determines whether galaxies reionized the early Universe. However, this escape fraction cannot be measured from high-redshift galaxies because the opacity of the intergalactic medium is large at high redshifts. Without methods to measure the escape fraction of high-redshift galaxies indirectly, it is unlikely that we will know what reionized the Universe. Here, we analyze the far-ultraviolet (UV) H I (Lyman series) and low-ionization metal absorption lines of nine low-redshift, confirmed Lyman continuum emitting galaxies. We use the H I covering fractions, column densities, and dust attenuations measured in a companion paper to predict the escape fraction of ionizing photons. We find good agreement between the predicted and observed Lyman continuum escape fractions (within 1.4σ) using both the H I and ISM absorption lines. The ionizing photons escape through holes in the H I, but we show that dust attenuation reduces the fraction of photons that escape galaxies. This means that the average high-redshift galaxy likely emits more ionizing photons than low-redshift galaxies. Two other indirect methods accurately predict the escape fractions: the Lyα escape fraction and the optical [O III]/[O II] flux ratio. We use these indirect methods to predict the escape fraction of a sample of 21 galaxies with rest-frame UV spectra but without Lyman continuum observations. Many of these galaxies have low escape fractions (fesc ≤ 1%), but 11 have escape fractions >1%. Future studies will use these methods to measure the escape fractions of high-redshift galaxies, enabling upcoming telescopes to determine whether star-forming galaxies reionized the early Universe.

scholarly journals Local star-forming dwarf galaxies as windows on reionization-era stellar populations

2019 ◽  
Vol 15 (S352) ◽  
pp. 316-316
Author(s):  
Peter Senchyna
Keyword(s):  
Line Emission ◽  
Stellar Populations ◽  
Star Forming ◽  
Star Models ◽  
Relative Paucity ◽  
High Ionization ◽  
Low Metallicity ◽  
Nearby Galaxies ◽  
A New Technique

AbstractThe recent detections of high-ionization nebular line emission from species including CIV in a number of z > 6 galaxies have highlighted substantial deficiencies in our understanding of metal poor stars. Prominent nebular CIV has never been detected in purely star-forming systems locally, and the massive star models used to model this emission in photoionization codes have not been empirically calibrated below the metallicity of the SMC (20% solar). As a result, we are presently entirely unprepared to correctly interpret nebular emission from metal-poor stars observed with JWST and ALMA in the reionization era. We present results from a multi-pronged ongoing local ultraviolet/optical observation campaign with HST/COS, Keck/ESI, and MMT designed to address this issue by locating and characterizing stellar populations capable of powering such high-ionization emission. This work has already demonstrated that strong nebular CIV can be powered by extremely metal-poor (< 10% solar) massive stars, indicating that we may already have evidence of such low-metallicity populations in the reionization era. However, CIV at the equivalent widths detected at z > 6 remains elusive locally, potentially in part due to the relative paucity of known nearby galaxies at these metallicities with massive stellar populations comparable to those in z > 6 systems. We present a new technique to locate such nearby galaxies, and results from optical follow-up which indicate that a substantial population of highly star- forming metal-poor galaxies likely resides just below the detection limits of previous large spectroscopic surveys.

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