Browsing by Author "Malhotra, S."
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- ItemA 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.
- ItemA large, deep 3 deg2 survey of H α, [O iii], and [O ii] emitters from LAGER: constraining luminosity functions(OUP, 2020) Khostovan, A. A.; Malhotra, S.; Rhoads, J. E.; Jiang, C.; Wang, J.; Wold, I.; Zheng, Z. Y.; Barrientos, Luis Felipe; Coughlin, A.; Harish, S.; Hu, W.; Infante Lira, Leopoldo; Perez, L. A.; Pharo, J.; Valdes, F.; Walker, A. R.; Yan, H.We present our measurements of the H α, [O iii], and [O ii] luminosity functions as part of the Lyman Alpha Galaxies at Epoch of Reionization (LAGER) survey using our samples of 1577 z = 0.47 H α-, 3933 z = 0.93 [O iii]-, and 5367 z = 1.59 [O ii]-selected emission line galaxies in a 3 deg 2 single, CTIO/Blanco DECam pointing of the COSMOS field. Our observations reach 5σ depths of 8.2 × 10 −18 erg s −1 cm −2 and comoving volumes of (1−7) × 10 5 Mpc 3 making our survey one of the deepest narrow-band surveys. We select our emission line galaxies via spectroscopic confirmation, photometric redshifts, and colour–colour selections. We measure the observed luminosity functions for each sample and find best fits of ϕ⋆=10−3.16+0.09−0.09 Mpc −3 and L⋆=1041.72+0.09−0.09 erg s −1 for H α, ϕ⋆=10−2.16+0.10−0.12 Mpc −3 and L⋆=1041.38+0.07−0.06 erg s −1 for [O iii], and ϕ⋆=10−1.97+0.07−0.07 Mpc −3 and L⋆=1041.66+0.03−0.03 erg s −1 for [O ii], with α fixed to −1.75, −1.6, and −1.3, respectively. An excess of bright >10 42 erg s −1 [O iii] emitters is observed and may be due to active galactic nucleus (AGN) contamination. Corrections for dust attenuation are applied assuming A Hα = 1 mag. We also design our own empirical rest-frame g − r calibration using SDSS DR12 data, test it against our z = 0.47 H α emitters with zCOSMOS 1D spectra, and calibrate it for (g − r) between −0.8 and 1.3 mag. Dust and AGN-corrected star formation rate densities (SFRDs) are measured as log 10 ρ SFR /(M ⊙ yr −1 Mpc −3 ) = −1.63 ± 0.04, −1.07 ± 0.06, and −0.90 ± 0.10 for H α, [O iii], and [O ii], respectively. We find our [O iii] and [O ii] samples fully trace cosmic star formation activity at their respective redshifts in comparison to multiwavelength SFRDs, while the H α sample traces ∼70 per cent of the total z = 0.47 SFRD.
- ItemCorrelations between H α equivalent width and galaxy properties at z = 0.47: Physical or selection-driven?(2021) Khostovan, A. A.; Malhotra, S.; Rhoads, J. E.; Harish, S.; Jiang, C.; Wang, J.; Wold, I.; Zheng, Z. -Y.; Barrientos, L. F.; Coughlin, A.; Hu, W.; Infante, L.; Perez, L. A.; Pharo, J.; Valdes, F.; Walker, A. R.The H alpha equivalent width (EW) is an observational proxy for specific star formation rate (sSFR) and a tracer of episodic, bursty star-formation activity. Previous assessments show that the H alpha EW strongly anticorrelates with stellar mass as M-0.25 similar to the sSFR - stellar mass relation. However, such a correlation could be driven or even formed by selection effects. In this study, we investigate how H alpha EW distributions correlate with physical properties of galaxies and how selection biases could alter such correlations using a z = 0.47 narrow-band-selected sample of 1572 H alpha emitters from the Ly alpha Galaxies in the Epoch of Reionization (LAGER) survey as our observational case study. The sample covers a 3 deg(2) area of COSMOS with a survey comoving volume of 1.1 x 10(5) Mpc(3). We assume an intrinsic EW distribution to form mock samples of H alpha emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that H alpha EW intrinsically correlates with stellar mass as W-0 proportional to M-0.16 +/- 0.03 and decreases by a factor of similar to 3 from 10(7) M-circle dot to 10(10) M-circle dot, while not correcting for selection effects steepens the correlation as M-025 +/- 0.04, We find low-mass H alpha emitters to be similar to 320 times more likely to have rest-frame EW > 200 angstrom compared to high-mass H alpha emitters. Combining the intrinsic W-0-stellar mass correlation with an observed stellar mass function correctly reproduces the observed H alpha luminosity function, while not correcting for selection effects underestimates the number of bright emitters. This suggests that the W-0-stellar mass correlation when corrected for selection effects is physically significant and reproduces three statistical distributions of galaxy populations (line luminosity function, stellar mass function, EW distribution). At lower stellar masses, we find there are more high-EW outliers compared to high stellar masses, even after we take into account selection effects. Our results suggest that high sSFR outliers indicative of bursty star formation activity are intrinsically more prevalent in low-mass H alpha emitters and not a byproduct of selection effects.
- ItemFirst 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
- ItemLyα 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.
- ItemThe 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.