Browsing by Author "Malhotra, S."

Now showing 1 - 5 of 5
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    A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies
    (IOP PUBLISHING LTD, 2017) Diaz Santos, T.; Armus, L.; Charmandaris, V.; Lu, N.; Stierwalt, S.; Stacey, G.; Malhotra, S.; van der Werf, P. P.; Howell, J. H.; Privon, G. C.; Mazzarella, J. M.; Goldsmith, P. F.; Murphy, E. J.; Barcos Munoz, L.; Linden, S. T.; Inami, H.; Larson, L.; Evans, A. S.; Appleton, P.; Iwasawa, K.; Lord, S.; Sanders, D. B.; Surace, J. A.
    We present an analysis of [O I](63), [O III](88), [N II](122), and [C II](158) far-infrared (FIR) fine-structure line observations obtained with Herschel/PACS, for similar to 240 local luminous infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey. We find pronounced declines ("deficits") of line-to-FIR continuum emission for [N II](122), [O I](63), and [C II](158) as a function of FIR color and infrared luminosity surface density, Sigma(IR). The median electron density of the ionized gas in LIRGs, based on the [N II](122)/[N II](205) ratio, is n(e) = 41 cm(-3). We find that the dispersion in the [C II](158) deficit of LIRGs is attributed to a varying fractional contribution of photodissociation regions (PDRs) to the observed [C II](158) emission, f ([C II](158)(PDR)) = [C II](158)(PDR)/C II](158), which increases from similar to 60% to similar to 95% in the warmest LIRGs. The [O I](63)/[C II](158)(PDR) ratio is tightly correlated with the PDR gas kinetic temperaturein sources where [O I] 63 is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, n(H), and intensity of the interstellar radiation field, G, in units of G(0) and find G/n(H) ratios of similar to 0.1-50 G(0) cm(3), with ULIRGs populating the upper end of the distribution. There is a relation between G/n(H) and Sigma(IR), showing a critical break at Sigma(IR)* similar or equal to 5 x 10(10) L-circle dot kpc(-2). Below Sigma(IR)*, G/n(H) remains constant, similar or equal to 0.32G(0) cm(3), and variations in Sigma(IR) are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. Above Sigma(IR)*, G/n(H) increases rapidly with Sigma(IR), signaling a departure from the typical PDR conditions found in normal star-forming galaxies toward more intense/harder radiation fields and compact geometries typical of starbursting sources.
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    A resolved Lyman α profile with doubly peaked emission at z∼7
    (EDP Sciences, 2024) Moya Sierralta, Cristobal; González López, Jorge; Infante Lira Leopoldo; Barrientos Parra, Luis Felipe; Hu, W.; Malhotra, S.; Rhoads, J.; Wang, J.; Wold, I.; Zheng, Z.
    © The Authors 2024.Context. The epoch of reionization is a landmark in structure formation and galaxy evolution. How it happened is still not clear, especially regarding which population of objects was responsible for contributing the bulk of ionizing photons to this process. Doubly peaked Lyman-alpha profiles in this epoch are of particular interest since they hold information about the escape of ionizing radiation and the environment surrounding the source. Aims. We wish to understand the escape mechanisms of ionizing radiation in Lyα emitters during this time and the origin of a doubly peaked Lyman-alpha profile. We also wish to estimate the size of a potential ionized bubble. Methods. Using radiative transfer models, we fit the line profile of a bright Lyα emitter at z-≈-6.9 using various gas geometries. The line modeling reveals significant radiation escape from this system. Results. The studied source shows significant escape (fesc(Lyα) ≈ 0.8, as predicted by the best fitting radiative transfer model) and appears to inhabit an ionized bubble of radius Rb-0.8-0.3+0.5-pMpc(tage/108)1/3. Radiative transfer modeling predicts the line to be completely redward of the systemic redshift. We suggest the line morphology is produced by inflows, by multiple components emitting Lyα, or by an absorbing component in the red wing. Conclusions. We propose that CDFS-1-s profile has two red peaks produced by winds within the system. Its high fesc(Lyα) and the low-velocity offset from the systemic redshift suggest that the source is an active ionizing agent. Future observations will reveal whether a peak is present blueward of the systemic redshift or if multiple components produce the profile.
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    First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z similar to 7
    (2017) Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, L. F.; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe
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    Lyα galaxies in the epoch of reionization (LAGER): spectroscopic confirmation of two redshift similar to ∼7.0 galaxies
    (2019) Yang, H.; Infante Lira, Leopoldo; Rhoads, J.E.; Hu, W.D.; Zheng, Z.Y.; Malhotra, S.; Wang, J.X.; Barrientos, Luis Felipe; Kang, W.Y.; Jiang, C.Y.
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    The Lyα Luminosity Function and Cosmic Reionization at z ∼ 7.0: A Tale of Two LAGER Fields
    (2019) Hu, W.D.; Wang, J.X.; Zheng, Z.Y.; Malhotra, S.; Rhoads, J.E.; Infante Lira, Leopoldo; Barrientos, Luis Felipe; Yang, H.; Jiang, C.Y.; Kang, W.Y.