scholarly journals Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters

2020 ◽  
Vol 493 (4) ◽  
pp. 5120-5130 ◽  
Author(s):  
Michael V Maseda ◽  
Roland Bacon ◽  
Daniel Lam ◽  
Jorryt Matthee ◽  
Jarle Brinchmann ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Equivalent Width ◽  
Production Efficiency ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Photon Production ◽  
Efficient Production ◽  
Number Counts ◽  
Lower Luminosity

ABSTRACT While low-luminosity galaxies dominate number counts at all redshifts, their contribution to cosmic reionization is poorly understood due to a lack of knowledge of their physical properties. We isolate a sample of 35 z ≈ 4–5 continuum-faint Lyman-α emitters from deep VLT/MUSE spectroscopy and directly measure their H α emission using stacked Spitzer/IRAC Ch. 1 photometry. Based on Hubble Space Telescope imaging, we determine that the average UV continuum magnitude is fainter than −16 (≈ 0.01 L⋆), implying a median Lyman-α equivalent width of 259 Å. By combining the H α measurement with the UV magnitude, we determine the ionizing photon production efficiency, ξion, a first for such faint galaxies. The measurement of log10 (ξion [Hz erg−1]) = 26.28 ($^{+0.28}_{-0.40}$) is in excess of literature measurements of both continuum- and emission line-selected samples, implying a more efficient production of ionizing photons in these lower luminosity, Lyman-α-selected systems. We conclude that this elevated efficiency can be explained by stellar populations with metallicities between 4 × 10−4 and 0.008, with light-weighted ages less than 3 Myr.

scholarly journals Diverse properties of Ly α emission in low-redshift compact star-forming galaxies with extremely high [O iii]/[O ii] ratios

2019 ◽  
Vol 491 (1) ◽  
pp. 468-482 ◽  
Author(s):  
Y I Izotov ◽  
D Schaerer ◽  
G Worseck ◽  
A Verhamme ◽  
N G Guseva ◽  
...  
Keyword(s):  
Emission Line ◽  
Equivalent Width ◽  
Hubble Space Telescope ◽  
Compact Star ◽  
Neutral Hydrogen ◽  
Low Oxygen ◽  
Indirect Measure ◽  
Star Forming ◽  
Peak Separation ◽  
High Emission

ABSTRACT We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of eight compact star-forming galaxies at redshifts z = 0.02811–0.06540, with low oxygen abundances 12 + log(O/H) = 7.43–7.82 and extremely high emission-line flux ratios O32 = [O iii] λ5007/[O ii] λ3727 ∼ 22–39, aiming to study the properties of Ly α emission in such conditions. We find a diversity in Ly α properties. In five galaxies Ly α emission line is strong, with equivalent width (EW) in the range 45–190 Å. In the remaining galaxies, weak Ly α emission with EW(Ly α) ∼ 2–7 Å is superposed on a broad Ly α absorption line, indicating a high neutral hydrogen column density N(H i) ∼ (1 – 3)× 1021 cm−2. We examine the relation between the Ly α escape fraction fesc(Ly α) and the Lyman continuum escape fraction fesc(LyC), using direct measures of the latter in eleven low-redshift LyC leakers, to verify whether fesc(Ly α) can be an indirect measure of escaping LyC radiation. The usefulness of O32, of the Ly α equivalent width EW(Ly α), and of the Ly α peak separation Vsep as indirect indicators of Ly α leakage is also discussed. It is shown that there is no correlation between O32 and fesc(Ly α). We find an increase of fesc(Ly α) with increasing EW(Ly α) for EW(Ly α) <100 Å, but for higher EW(Ly$\alpha)\gtrsim$150 Å the fesc(Ly α) is nearly constant attaining the value of ∼0.25. We find an anticorrelation between fesc(Ly α) and Vsep, though not as tight as the one found earlier between fesc(LyC) and Vsep. This finding makes Vsep a promising indirect indicator of both the Ly α and ionizing radiation leakage.

Properties of LBGs with [OIII] detection at z > 3: The importance of including nebular emission data in SED fitting

2019 ◽  
Vol 15 (S341) ◽  
pp. 201-205
Author(s):  
Fang-Ting Yuan ◽  
Denis Burgarella ◽  
David Corre ◽  
Veronique Buat ◽  
Médéric Boquien ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Equivalent Width ◽  
Spectroscopic Data ◽  
Rest Frame ◽  
High Redshift ◽  
Emission Lines ◽  
Emission Data ◽  
Strong Emission ◽  
The Difference

AbstractAt high redshift, the contribution of strong emission lines to the broadband photometry can cause large uncertainties when estimating galaxy physical properties. To examine this effect, we investigate a sample of 54 LBGs at 3 < zspec < 3.8 with detected [OIII] line emissions. We use CIGALE to fit simultaneously the rest-frame UV-to-NIR SEDs of these galaxies and their emission line data. By comparing the results with and without emission line data, we show that spectroscopic data are necessary to constrain the nebular model. We examine the K-band excess, which is usually used to estimate the emissions of [OIII]+Hβ lines when there is no spectral data, and find that the difference between the estimation and observation can reach up to > 1 dex for some galaxies, showing the importance of obtaining spectroscopic measurements of these lines. We also estimate the equivalent width of the Hβ absorption and find it negligible compared to the Hβ emission.

scholarly journals Hubble Space Telescope Observations of [O III] Emission in Nearby QSO2s: Physical Properties of the Ionised Outflows

2020 ◽  
Author(s):  
Anna Trindade Falcão ◽  
S B Kraemer ◽  
T C Fischer ◽  
D M Crenshaw ◽  
M Revalski ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Hubble Space Telescope ◽  
Radial Distance ◽  
Flow Rates ◽  
Space Telescope ◽  
Bolometric Luminosity ◽  
Mass Outflow ◽  
Peak Outflow ◽  
Imaging Spectrograph

Abstract We use Hubble Space Telescope (HST)/ Space Telescope Imaging Spectrograph (STIS) long-slit G430M and G750M spectra to analyse the extended [O III] λ5007 emission in a sample of twelve nearby (z &gt;0.12) luminous (Lbol &gt; 1.6 × 1045 erg s−1) QSO2s. The purpose of the study is to determine the properties of the mass outflows of ionised gas and their role in AGN feedback. We measure fluxes and velocities as functions of radial distances. Using Cloudy models and ionising luminosities derived from [O III] λ5007, we are able to estimate the densities for the emission-line gas. From these results, we derive masses of [O III]-emitting gas, mass outflow rates, kinetic energies, kinetic luminosities, momenta and momentum flow rates as a function of radial distance for each of the targets. For the sample, masses are several times 103M⊙ − 107M⊙ and peak outflow rates are 9.3 × 10−3M⊙ yr−1 to 10.3 M⊙ yr−1. The peak kinetic luminosities are 3.4 × 10−8 to 4.9 × 10−4 of the bolometric luminosity, which does not approach the 5.0 × 10−3 - 5.0 × 10−2 range required by some models for efficient feedback. For Mrk 34, which has the largest kinetic luminosity of our sample, in order to produce efficient feedback there would have to be 10 times more [O III]-emitting gas than we detected at its position of maximum kinetic luminosity. Three targets show extended [O III] emission, but compact outflow regions. This may be due to different mass profiles or different evolutionary histories.

scholarly journals Physical Properties of Nearby Dwarf Elliptical Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 69-69
Author(s):  
M. R. Seo ◽  
H. B. Ann
Keyword(s):  
Physical Properties ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
High Density ◽  
Emission Lines ◽  
Dwarf Elliptical Galaxies ◽  
Nuclear Regions

AbstractMost dwarf elliptical galaxies except for ‘dE, N’ galaxies which are characterized by young stellar populations in the nuclear regions are located in the high density environment. The colors and spectra of ‘dE, N’ galaxies are different from other types, in the sense that they have redder colors with little emission lines. The majority of dwarf elliptical galaxies are younger than 7 Gyr with metallicity larger than [z/H]=−0.5.

Spitzer and Hubble Space Telescope Constraints on the Physical Properties of the z  ~ 7 Galaxy Strongly Lensed by A2218

2004 ◽  
Vol 618 (1) ◽  
pp. L5-L8 ◽  
Author(s):  
E. Egami ◽  
J.-P. Kneib ◽  
G. H. Rieke ◽  
R. S. Ellis ◽  
J. Richard ◽  
...  
Keyword(s):  
Physical Properties ◽  
Hubble Space Telescope ◽  
Space Telescope

scholarly journals Pigment Production under Cold Stress in the Green Microalga Chlamydomonas reinhardtii

Agriculture ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 564
Author(s):  
Supakorn Potijun ◽  
Chonlada Yaisamlee ◽  
Anchalee Sirikhachornkit
Keyword(s):  
Cold Stress ◽  
Chlamydomonas Reinhardtii ◽  
Production Efficiency ◽  
Cell Physiology ◽  
Efficient Production ◽  
Increase Production Efficiency ◽  
Whole Cells ◽  
Stress Acclimation ◽  
Chlorophyll Accumulation ◽  
In The Wild

Microalgae have long been used for the commercial production of natural colorants such as carotenoids and chlorophyll. Due to the rising demand for carotenoids and other natural products from microalgae, strategies to increase production efficiency are urgently needed. The production of microalgal biorefineries has been limited to countries with moderate climates. For countries with cooler climates and less daylight, methodologies for the efficient production of microalgal biorefineries need to be investigated. Algal strains that can be safely consumed as whole cells are also attractive alternatives for developing as carotenoid supplements, which can also contain other compounds with health benefits. Using such strains helps to eliminate the need for hazardous solvents for extraction and several other complicated steps. In this study, the mesophilic green alga Chlamydomonas reinhardtii was employed to study the effects of cold stress on cell physiology and the production of pigments and storage compounds. The results showed that temperatures between 10 and 20 °C induced carotenoid and chlorophyll accumulation in the wild-type strain of C. reinhardtii. Interestingly, the increased level of carotenoids suggested that they might play a crucial role in cold stress acclimation. A temperature of 15 °C resulted in the highest carotenoid and chlorophyll productivity. At this temperature, carotenoid and chlorophyll productivity was 2 times and 1.3 times higher than at 25 °C, respectively. Subjecting a mutant defective in lutein and zeaxanthin accumulation to cold stress revealed that these two carotenoids are not essential for cold stress survival. Therefore, cold temperature could be used as a strategy to induce and increase the productivity of pigments in C. reinhardtii.

REQUIEM-2D Methodology: Spatially Resolved Stellar Populations of Massive Lensed Quiescent Galaxies from Hubble Space Telescope 2D Grism Spectroscopy

2020 ◽  
Vol 900 (2) ◽  
pp. 184 ◽  
Author(s):  
Mohammad Akhshik ◽  
Katherine E. Whitaker ◽  
Gabriel Brammer ◽  
Guillaume Mahler ◽  
Keren Sharon ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Space Telescope ◽  
Spatially Resolved

scholarly journals Do quasars evolve over cosmological time scales?

1986 ◽  
Vol 119 ◽  
pp. 439-445
Author(s):  
E.J. Wampler ◽  
D. Ponz
Keyword(s):  
Emission Line ◽  
Time Scales ◽  
Line Strength ◽  
Schmidt Telescope ◽  
Spectral Evolution ◽  
General Correlation ◽  
Cosmological Time ◽  
Systematic Biases ◽  
Evolution Laws ◽  
Lower Luminosity

Systematic biases that are redshift dependent can influence the optical discovery of quasars and the evolution laws derived from counts of quasars. New data and their interpretation for quasars brighter than MB = −24 in the Palomar Bright Quasar Survey (BQS) (Schmidt and Green, 1983) are consistent with no evolution. A comparison of BQS quasars with the brightest quasars from the CTIO Schmidt Telescope Survey (Osmer and Smith, 1980) shows that if qo is near zero, the co-moving density of bright quasars in a Friedmann cosmology is about 15 times higher for the CTIO survey quasars (mean z ≈ 2.8) than for the BQS quasars (mean z ≈ 1.8). In this case spectral evolution is also required since the CTIO quasars have stronger CIV λ1548 lines than the BQS quasars of similar luminosity. Alternatively, if qO is taken to be near 1, the CTIO survey quasars would then have lower luminosity than the BQS quasars and these data would be consistent with no evolution. Strong CIV λ1548 lines for the CTIO quasars would then fit the general correlation between absolute quasar luminosity and emission line strength (Wampler, Gaskell, Burke and Baldwin, 1984).

scholarly journals Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 19-28
Author(s):  
Puragra Guhathakurta ◽  
Brian Yanny ◽  
Donald P. Schneider ◽  
John N. Bahcall
Keyword(s):  
Density Profile ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Core Collapse ◽  
Red Giants ◽  
Space Telescope ◽  
Blue Straggler ◽  
Central Regions ◽  
Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

scholarly journals The Ionizing Photon Production Efficiency (ξ ion) of Lensed Dwarf Galaxies at z ∼ 2

2020 ◽  
Vol 895 (2) ◽  
pp. 116 ◽  
Author(s):  
Najmeh Emami ◽  
Brian Siana ◽  
Anahita Alavi ◽  
Timothy Gburek ◽  
William R. Freeman ◽  
...  
Keyword(s):  
Production Efficiency ◽  
Dwarf Galaxies ◽  
Photon Production
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