Finding the UV–Visible Path Forward: Proceedings of the Community Workshop to Plan the Future of UV/Visible Space Astrophysics

Scowen, Paul A.; Tripp, Todd M.; Beasley, Matt; Ardila, D. R.; Andersson, B. G.; Apellániz, J. Maíz; Barstow, M. A.; Bianchi, Luciana; Calzetti, Daniela; Clampin, Mark; Evans, Christopher J.; García, Miriam García; Castro, Ana Gomez De; Harris, W. M.; Hartigan, Patrick; Howk, J. C.; Hutchings, J. B.; Larruquert, Juan I.; Lillie, Charles F.; Matthews, Gary; McCandliss, Stephan R.; Polidan, R.; Pérez, M. R.; Rafelski, Marc; Roederer, Ian U.; Sana, H.; Sanders, W. T.; Schiminovich, David; Thronson, H. A.; Tumlinson, Jason; Vallerga, J. V.; Wofford, Aida

doi:10.1088/1538-3873/129/977/076001

Cited by 14 publications

(6 citation statements)

References 115 publications

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“…What is truly needed are much more stringent escape fraction measurements for fainter/lower-mass galaxies. This would require a leap in our space-based ultraviolet imaging or spectroscopic capabilities, which is the focus of several concepts for future space missions (Scowen et al 2017;McCandliss & O'Meara 2017). However, fainter galaxies have begun to be probed.…”

Section: Comparison To Observationsmentioning

confidence: 99%

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Finkelstein

D’Aloisio

Paardekooper

et al. 2019

ApJ

345

296

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We explore scenarios for reionizing the intergalactic medium with low galaxy ionizing photon escape fractions. We combine simulation-based halo-mass dependent escape fractions with an extrapolation of the observed galaxy rest-ultraviolet luminosity functions to solve for the reionization history from z = 20 → 4. We explore the posterior distributions for key unknown quantities, including the limiting halo mass for star-formation, the ionizing photon production efficiency, and a potential contribution from active galactic nuclei (AGN). We marginalize over the allowable parameter space using a Markov Chain Monte Carlo method, finding a solution which satisfies the most model-independent constraints on reionization. Our fiducial model can match observational constraints with an average escape fraction of <5% throughout the bulk of the epoch of reionization if: i ) galaxies form stars down to the atomic cooling limit before reionization and a photosuppression mass of log (M h /M ) ∼ 9 during/after reionization (−13 < M UV,lim < −11); ii ) galaxies become more efficient producers of ionizing photons at higher redshifts and fainter magnitudes, and iii ) there is a significant, but sub-dominant, contribution by AGN at z 7. In this model the faintest galaxies (M UV > −15) dominate the ionizing emissivity, leading to an earlier start to reionization and a smoother evolution of the ionized volume filling fraction than models which assume a single escape fraction at all redshifts and luminosities. The ionizing emissivity from this model is consistent with observations at z=4-5 (and below, when extrapolated), in contrast to some models which assume a single escape fraction. Our predicted ionized volume filling fraction at z = 7 of Q H II = 78% (± 8%) is in modest (∼1-2σ) tension with observations of Lyα emitters at z ∼ 7 and the damping wing analyses of the two known z > 7 quasars, which prefer Q H II ,z=7 ∼ 40-50%.

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Section: Comparison To Observationsmentioning

confidence: 99%

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Finkelstein

D’Aloisio

Paardekooper

et al. 2019

ApJ

345

296

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“…The next challenges of the astrophysics community require more efficient optical coatings, particularly in the far UV (FUV, λ: 100-200 nm) [1][2][3][4]. Aluminum is the single material choice to efficiently reflect a broad spectrum ranging from the FUV to the infrared and beyond.…”

Section: Introductionmentioning

confidence: 99%

Optimization of MgF₂-deposition temperature for far UV Al mirrors

et al. 2018

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Progress towards far UV (FUV) coatings with enhanced reflectance is invaluable for future space missions, such as LUVOIR. This research starts with the procedure developed to enhance MgF-protected Al reflectance through depositing MgF on a heated aluminized substrate [Quijada et al., Proc. SPIE 8450, 84502H (2012)] and it establishes the optimum deposition temperature of the MgF protective film for Al mirrors with a reflectance as high as ~90% at 121.6 nm. Al films were deposited at room temperature and protected with a MgF film deposited at various temperatures ranging from room temperature to 350°C. It has been found that mirror reflectance in the short FUV range continuously increases with MgF deposition temperature up to 250°C, whereas reflectance decreases at temperatures of 300°C and up. The short-FUV reflectance of mirrors deposited at 250°C only slightly decreased over time by less than 1%, compared to a larger decay for standard coatings prepared at room temperature. Al mirrors protected with MgF deposited at room temperature that were later annealed displayed a similar reflectance enhancement that mirrors protected at high temperatures. MgF and Al roughness as well as MgF density were analyzed by x-ray grazing incidence reflectometry. A noticeable reduction in both Al and MgF roughness, as well as an increase of MgF density, were measured for films deposited at high temperatures. On the other hand, it was found a strong correlation between the protective-layer deposition temperature (or post-deposition annealing temperature) and the pinhole open area in Al films, which could be prevented with a somewhat thicker Al film.

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“…Figure 6 displays XRR data and fits for some samples. In the fits, the density of Al was set at 2.7 g/cm 3 .…”

Section: Structural Propertiesmentioning

confidence: 99%

“…Fluoride films are known to grow with a reduced packing density due to the presence of pores, which originates in the low mobility of condensing molecules at film growth on a low-temperature substrate. Evolution of AlF3 density with deposition temperature can be interpreted as an increase of packing density, with the film approaching bulk density of ~2.88 g/cm 3 .…”

Section: Structural Propertiesmentioning

confidence: 99%

“…The far ultraviolet (FUV; here it refers to the 100-200-nm spectral range) encloses spectral lines of many fundamental atom and ion species of H, C, N, O, etc. ; observation at such spectral lines is key for the communities of astronomy and astrophysics [1][2][3][4][5], solar physics [6], as well as atmosphere physics. Aluminum is the material with the largest reflectance down to the FUV [7].…”

Section: Introductionmentioning

confidence: 99%

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Temperature Dependence of AlF3 Protection on Far-UV Al Mirrors

et al. 2019

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More efficient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, and morphology of AlF3-protected Al mirrors have been investigated as a function of deposition temperature of the AlF3 film. In this work, it is shown how AlF3 deposition temperature is an important parameter whose optimization ultimately yields valuable throughput enhancement and improved endurance to large storage periods. Al films were deposited at room temperature (RT) and AlF3 protective layers were deposited at temperatures ranging from RT to 350 °C. It was found that the optimum AlF3 deposition temperature was between 200 and 250 °C, yielding the largest FUV reflectance and a better stability of the mirrors, which had been stored in a desiccator environment. Increasing AlF3 deposition temperature resulted in an increase in film density, approaching bulk density at 250 °C. The morphology of Al and AlF3 films as a function of AlF3 deposition temperature was also investigated. The increase in the AlF3 deposition temperature resulted in a decrease of both Al and AlF3 surface roughness and in the growth of the grain width at the AlF3 outer surface. It also resulted in a trend for the prevalent (111) planes of Al nanocrystals to orient parallel to the coating surface.

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Finding the UV–Visible Path Forward: Proceedings of the Community Workshop to Plan the Future of UV/Visible Space Astrophysics

Cited by 14 publications

References 115 publications

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Optimization of MgF₂-deposition temperature for far UV Al mirrors

Temperature Dependence of AlF3 Protection on Far-UV Al Mirrors

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Finding the UV–Visible Path Forward: Proceedings of the Community Workshop to Plan the Future of UV/Visible Space Astrophysics

Cited by 14 publications

References 115 publications

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction

Optimization of MgF2-deposition temperature for far UV Al mirrors

Temperature Dependence of AlF3 Protection on Far-UV Al Mirrors

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Product

Resources

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Optimization of MgF₂-deposition temperature for far UV Al mirrors