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Mean H{alpha}+[N II]+[S II] EW inferred for star-forming galaxies at z ~ 5.1-5.4 using high-quality Spitzer/IRAC photometry (2016)

Rasappu, N., Smit, R., Labbe, I., Bouwens, R. J., Stark, D. P., Ellis, R. S., Oesch, P. A.

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society

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Publication Date: 2016-07-25

Description: Recent Spitzer /InfraRed Array Camera (IRAC) photometric observations have revealed that rest-frame optical emission lines contribute significantly to the broad-band fluxes of high-redshift galaxies. Specifically, in the narrow redshift range z ~ 5.1–5.4 the [3.6]–[4.5] colour is expected to be very red, due to contamination of the 4.5 μm band by the dominant Hα line, while the 3.6 μm filter is free of nebular emission lines. We take advantage of new reductions of deep Spitzer /IRAC imaging over the Great Observatories Origins Deep Survey-North+South fields (Labbé et al. 2015 ) to obtain a clean measurement of the mean Hα equivalent width (EW) from the [3.6]–[4.5] colour in the redshift range z = 5.1–5.4. The selected sources either have measured spectroscopic redshifts (13 sources) or lie very confidently in the redshift range z = 5.1–5.4 based on the photometric redshift likelihood intervals (11 sources). Our z phot = 5.1–5.4 sample and z spec = 5.10–5.40 spectroscopic sample have a mean [3.6]–[4.5] colour of 0.31 ± 0.05 and 0.35 ± 0.07 mag, implying a rest-frame EW (Hα+[N ii ]+[S ii ]) of 665 ± 53 and 707 ± 74 Å, respectively, for sources in these samples. These values are consistent albeit slightly higher than derived by Stark et al. at z ~ 4, suggesting an evolution to higher values of the Hα+[N ii ]+[S ii ] EW at z 〉 2. Using the 3.6 μm band, which is free of emission line contamination, we perform robust spectral energy distribution fitting and find a median specific star formation rate of sSFR = $17_{-5}^{+2}$ Gyr –1 , $7_{-2}^{+1}\times$ higher than at z ~ 2. We find no strong correlation (〈2) between the Hα+[N ii ]+[S ii ] EW and the stellar mass of sources. Before the advent of JWST , improvements in these results will come through an expansion of current spectroscopic samples and deeper Spitzer /IRAC measurements.

Print ISSN: 0035-8711

Electronic ISSN: 1365-2966

Topics: Physics

Published by Oxford University Press

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Calcium regulation during stimulus-secretion coupling: continuous measurement of intracellular calcium activities (1980)

J. O'Doherty ; S. J. Youmans ; W. M. Armstrong ; [et al.]

American Association for the Advancement of Science (AAAS)

In: Science. 209(4455): 510-3.

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Publication Date: 1980-07-25

Description: Accurate measurements of intracellular calcium activities in salivary gland epithelial cells of the insect Phormia regina were obtained with microelectrodes in which N,N'-di(11-ethoxycarbonyl)undecyl-N,N'-4,5-tetramethyl-3,6-dioxaoctane diacid diamide wsa incorporated in a liquid membrane system. When calibrated in solutions approximating the ionic concentration of the cell interior, these microelectrodes gave rapid stable responses that were linear functions of the logarithm of calcium activities and were not affected by potassium, sodium and magnesium. Continuous monitoring of calcium activities during serotonin-induced saliva release provided direct evidence of hormonal influence on transmembrane calcium movement and spontaneous regulation of intracellular calcium by stimulated cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Doherty, J -- Youmans, S J -- Armstrong, W M -- Stark, R J -- New York, N.Y. -- Science. 1980 Jul 25;209(4455):510-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7394518" target="_blank"〉PubMed〈/a〉

Keywords: Animals ; Biological Transport/drug effects ; Calcium/*metabolism ; Diptera/*metabolism ; Epithelium/metabolism ; Kinetics ; Magnesium/pharmacology ; Microelectrodes ; Salivary Glands/drug effects/*metabolism ; Serotonin/pharmacology

Print ISSN: 0036-8075

Electronic ISSN: 1095-9203

Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics