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. (2021). Correlations between Hα equivalent width and galaxy properties at z = 0.47: Physical or selection-driven? MNRAS, 503, 5115K.
The Hα 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 Hα 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 α 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 Hα emitters from the Lyα 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\times10^5 Mpc^3. We assume an intrinsic EW distribution to form mock samples of Hα emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that Hα EW intrinsically correlates with stellar mass as W_0 ∝M^-0.16\pm0.03 and decreases by a factor of \sim3 from 10^7 M_⊙ to 10^10 M_⊙, while not correcting for selection effects steepens the correlation as M^-0.25\pm0.04. We find low-mass Hα emitters to be \sim320 times more likely to have rest-frame EW>200 Å compared to high-mass Hα emitters. Combining the intrinsic W_0-stellar mass correlation with an observed stellar mass function correctly reproduces the observed Hα 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 Hα$ emitters and not a byproduct of selection effects.
Khostovan, A. A., Malhotra, S., Rhoads, J. E., Jiang, C., Wang, J., Wold, I., Zheng, Z.-Y., Barrientos, L. F., Coughlin, A., Harish, S., Hu, W., Infante, L., Perez, L. A., Pharo, J., Valdes, F., Walker, A. R., & Yang, H. (2020). A large, deep 3 deg^2 survey of Hα, [OIII], and [OII] emitters from LAGER: constraining luminosity functions. MNRAS, 493, 3966K.
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 deg2 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) × 105 Mpc3 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^⋆= 10^41.72^+0.09_-0.09 erg s-1 for H α, φ ^⋆= 10^-2.16^+0.10_-0.12 Mpc-3 and L^⋆= 10^41.38^+0.07_-0.06 erg s-1 for [O III], and φ ^⋆= 10^-1.97^+0.07_-0.07 Mpc-3 and L^⋆= 10^41.66^+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 >1042 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 AHα = 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 log10ρSFR/(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.
Khostovan, A. A., Sobral, D., Mobasher, B., Matthee, J., Cochrane, R. K., Chartab, N., Jafariyazani, M., Paulino-Afonso, A., Santos, S., & Calhau, J. (2019). The clustering of typical Lyα emitters from z ∼2.5-6: host halo masses depend on Lyαand UV luminosities. MNRAS, 489, 555K.
We investigate the clustering and halo properties of ∼5000 Ly α-selected emission-line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between z ∼ 2.5 and 6. We measure clustering lengths of r0 ∼ 3-6 h-1 Mpc and typical halo masses of ∼1011 M⊙ for our narrowband-selected LAEs with typical LLy α ∼ 1042-43 erg s-1. The intermediate-band-selected LAEs are observed to have r0 ∼ 3.5-15 h-1 Mpc with typical halo masses of ∼1011-12 M⊙ and typical LLy α ∼ 1043-43.6 erg s-1. We find a strong, redshift-independent correlation between halo mass and Ly α luminosity normalized by the characteristic Ly α luminosity, L⋆(z). The faintest LAEs (L ∼ 0.1 L⋆(z)) typically identified by deep narrowband surveys are found in 1010 M⊙ haloes and the brightest LAEs (L ∼ 7 L⋆(z)) are found in ∼5 × 1012 M⊙ haloes. A dependency on the rest-frame 1500 Å UV luminosity, MUV, is also observed where the halo masses increase from 1011 to 1013 M⊙ for MUV ∼ -19 to -23.5 mag. Halo mass is also observed to increase from 109.8 to 1012 M⊙ for dust-corrected UV star formation rates from ∼0.6 to 10 M⊙ yr-1 and continues to increase up to 1013 M⊙ in halo mass, where the majority of those sources are active galactic nuclei. All the trends we observe are found to be redshift independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe.
Khostovan, A. A., Sobral, D., Mobasher, B., Best, P. N., Smail, I., Matthee, J., Darvish, B., Nayyeri, H., Hemmati, S., & Stott, J. P. (2018). The clustering of Hβ+ [OIII] and [OII] emitters since z ∼5: dependencies with line luminosity and stellar mass. MNRAS, 478, 2999K.
We investigate the clustering properties of ∼7000 H β + [O III] and [O II] narrowband-selected emitters at z ∼ 0.8-4.7 from the High-z Emission Line Survey. We find clustering lengths, r0, of 1.5-4.0 h-1 Mpc and minimum dark matter halo masses of 1010.7-12.1 M⊙ for our z = 0.8-3.2 H β + [O III] emitters and r0 ∼ 2.0-8.3 h-1 Mpc and halo masses of 1011.5-12.6 M⊙ for our z = 1.5-4.7 [O II] emitters. We find r0 to strongly increase both with increasing line luminosity and redshift. By taking into account the evolution of the characteristic line luminosity, L⋆(z), and using our model predictions of halo mass given r0, we find a strong, redshift-independent increasing trend between L/L⋆(z) and minimum halo mass. The faintest H β + [O III] emitters are found to reside in 109.5 M⊙ haloes and the brightest emitters in 1013.0 M⊙ haloes. For [O II] emitters, the faintest emitters are found in 1010.5 M⊙ haloes and the brightest emitters in 1012.6 M⊙ haloes. A redshift-independent stellar mass dependency is also observed where the halo mass increases from 1011 to 1012.5 M⊙ for stellar masses of 108.5 to 1011.5 M⊙, respectively. We investigate the interdependencies of these trends by repeating our analysis in a Lline-Mstar grid space for our most populated samples (H β + [O III] z = 0.84 and [O II] z = 1.47) and find that the line luminosity dependency is stronger than the stellar mass dependency on halo mass. For L > L⋆ emitters at all epochs, we find a relatively flat trend with halo masses of 1012.5-13 M⊙, which may be due to quenching mechanisms in massive haloes that is consistent with a transitional halo mass predicted by models.
Khostovan, A. A., Sobral, D., Mobasher, B., Smail, I., Darvish, B., Nayyeri, H., Hemmati, S., & Stott, J. P. (2016). The nature of Hβ+[OIII] and [OII] emitters to z ∼5 with HiZELS: stellar mass functions and the evolution of EWs. MNRAS, 463, 2363K.
We investigate the properties of ∼7000 narrow-band selected galaxies with strong Hβ+[O III] and [O II] nebular emission lines from the High-z Emission-Line Survey between z ∼ 0.8 and 5.0. Our sample covers a wide range in stellar mass (Mstellar ∼ 107.5-12.0 M⊙), rest-frame equivalent widths (EWrest∼10-105 Å), and line luminosities (Lline ∼ 1040.5-43.2 erg s-1). We measure the Hβ+[O III]-selected stellar mass functions out to z ∼ 3.5 and find that both M⋆ and φ⋆ increases with cosmic time. The [O II]-selected stellar mass functions show a constant M⋆ ≈ 1011.6 M⊙ and a strong, increasing evolution with cosmic time in φ⋆ in line with Hα studies. We also investigate the evolution of the EWrest as a function of redshift with a fixed mass range (109.5-10.0 M⊙) and find an increasing trend best represented by (1 + z)3.81 ± 0.14 and (1 + z)2.72 ± 0.19 up to z ∼ 2 and ∼3 for Hβ+[O III] and [O II] emitters, respectively. This is the first time that the EWrest evolution has been directly measured for Hβ+[O III] and [O II] emitters up to these redshifts. There is evidence for a slower evolution for z > 2 in the Hβ+[O III] EWrest and a decreasing trend for z > 3 in the [O II] EWrest evolution, which would imply low [O II] EW at the highest redshifts and higher [O III]/[O II] line ratios. This suggests that the ionization parameter at higher redshift may be significantly higher than the local Universe. Our results set the stage for future near-IR space-based spectroscopic surveys to test our extrapolated predictions and also produce z > 5 measurements to constrain the high-z end of the EWrest and [O III]/[O II] evolution.
Khostovan, A. A., Sobral, D., Mobasher, B., Best, P. N., Smail, I., Stott, J. P., Hemmati, S., & Nayyeri, H. (2015). Evolution of the Hβ+ [OIII] and [OII] luminosity functions and the [OII] star formation history of the Universe up to z ∼5 from HiZELS. MNRAS, 452, 3948K.
We investigate the evolution of the H β + [O III] and [O II] luminosity functions from z ∼ 0.8 to ∼5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). This is the first time that the H β + [O III] and [O II] luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of [O II] and H β + [O III] emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ∼1 × 106 Mpc-3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour-colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L⋆ and a decrease in φ⋆ for both H β + [O III] and [O II] emitters. We derive the [O II] star formation history of the Universe since z ∼ 5 and find that the cosmic star formation rate density (SFRD) rises from z ∼ 5 to ∼3 and then drops towards z ∼ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ∼ 5 based only on a single tracer of star formation. When comparing the H β + [O III] SFRDs to the [O II] and H α SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the H β + [O III] sample is dominated by star-forming galaxies at high-z rather than AGNs.
In The Pipeline
Khostovan, A. A. et al. (2024). COSMOS Spectroscopic Compilation (working title).
Khostovan, A. A. et al. (2024). COSMOS Spectroscopic Archive I. Subaru/FMOS (working title).
Khostovan, A. A. et al. (2024). COSMOS Spectroscopic Archive II. Gemini/GMOS (working title).
Khostovan, A. A. et al. (2024). COSMOS Spectroscopic Archive III. Intense Extreme Emission Line Galaxy at z ∼0.8 : Analog of high-z star-forming galaxies (working title).
2023
Rezaee, S., Reddy, N. A., Topping, M. W., Shivaei, I., Shapley, A. E., Fetherolf, T., Kriek, M., Coil, A., Mobasher, B., Siana, B., Du, X., Khostovan, A. A., Weldon, A., Emami, N., & Chartab, N. (2023). Exploring the correlation between H\ensuremathα-to-UV ratio and burstiness for typical star-forming galaxies at z 2. MNRAS, 526(1), 1512–1527. https://doi.org/10.1093/mnras/stad2842
Casey, C. M., Kartaltepe, J. S., Drakos, N. E., Franco, M., Harish, S., Paquereau, L., Ilbert, O., Rose, C., Cox, I. G., Nightingale, J. W., Robertson, B. E., Silverman, J. D., Koekemoer, A. M., Massey, R., McCracken, H. J., Rhodes, J., Akins, H. B., Allen, N., Amvrosiadis, A., … Zavala, J. A. (2023). COSMOS-Web: An Overview of the JWST Cosmic Origins Survey. ApJ, 954(1), 31. https://doi.org/10.3847/1538-4357/acc2bc
2022
Harish, S., Wold, I. G. B., Malhotra, S., Rhoads, J. E., Hu, W., Wang, J., Zheng, Z.-ya, Barrientos, L. F., González-López, J., Perez, L. A., Khostovan, A. A., Infante, L., Jiang, C., Moya-Sierralta, C., Pharo, J., Valdes, F., & Yang, H. (2022). New Spectroscopic Confirmations of Ly\ensuremathα Emitters at Z 7 from the LAGER Survey. ApJ, 934(2), 167. https://doi.org/10.3847/1538-4357/ac7cf1
Wold, I. G. B., Malhotra, S., Rhoads, J., Wang, J., Hu, W., Perez, L. A., Zheng, Z.-Y., Khostovan, A. A., Walker, A. R., Barrientos, L. F., González-López, J., Harish, S., Infante, L., Jiang, C., Pharo, J., Moya-Sierralta, C., Bauer, F. E., Galaz, G., Valdes, F., & Yang, H. (2022). LAGER Ly\ensuremathα Luminosity Function at z 7: Implications for Reionization. ApJ, 927(1), 36. https://doi.org/10.3847/1538-4357/ac4997
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. (2021). Correlations between Hα equivalent width and galaxy properties at z = 0.47: Physical or selection-driven? MNRAS, 503, 5115K.
The Hα 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 Hα 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 α 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 Hα emitters from the Lyα 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\times10^5 Mpc^3. We assume an intrinsic EW distribution to form mock samples of Hα emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that Hα EW intrinsically correlates with stellar mass as W_0 ∝M^-0.16\pm0.03 and decreases by a factor of \sim3 from 10^7 M_⊙ to 10^10 M_⊙, while not correcting for selection effects steepens the correlation as M^-0.25\pm0.04. We find low-mass Hα emitters to be \sim320 times more likely to have rest-frame EW>200 Å compared to high-mass Hα emitters. Combining the intrinsic W_0-stellar mass correlation with an observed stellar mass function correctly reproduces the observed Hα 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 Hα$ emitters and not a byproduct of selection effects.
Rezaee, S., Reddy, N., Shivaei, I., Fetherolf, T., Emami, N., & Khostovan, A. A. (2021). Variation of the nebular dust attenuation curve with the properties of local star-forming galaxies. MNRAS, 506(3), 3588–3595. https://doi.org/10.1093/mnras/stab1885
Santos, S., Sobral, D., Butterworth, J., Paulino-Afonso, A., Ribeiro, B., da Cunha, E., Calhau, J., Khostovan, A. A., Matthee, J., & Arrabal Haro, P. (2021). The evolution of the UV luminosity and stellar mass functions of Lyman-\ensuremathα emitters from z 2 to z 6. MNRAS, 505(1), 1117–1134. https://doi.org/10.1093/mnras/stab1218
Hu, W., Wang, J., Infante, L., Rhoads, J. E., Zheng, Z.-Y., Yang, H., Malhotra, S., Barrientos, L. F., Jiang, C., González-López, J., Prieto, G., Perez, L. A., Hibon, P., Galaz, G., Coughlin, A., Harish, S., Kong, X., Kang, W., Khostovan, A. A., … Zheng, X. Z. (2021). A Lyman-\ensuremathα protocluster at redshift 6.9. Nature Astronomy, 5, 485–490. https://doi.org/10.1038/s41550-020-01291-y
2020
Khostovan, A. A., Malhotra, S., Rhoads, J. E., Jiang, C., Wang, J., Wold, I., Zheng, Z.-Y., Barrientos, L. F., Coughlin, A., Harish, S., Hu, W., Infante, L., Perez, L. A., Pharo, J., Valdes, F., Walker, A. R., & Yang, H. (2020). A large, deep 3 deg^2 survey of Hα, [OIII], and [OII] emitters from LAGER: constraining luminosity functions. MNRAS, 493, 3966K.
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 deg2 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) × 105 Mpc3 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^⋆= 10^41.72^+0.09_-0.09 erg s-1 for H α, φ ^⋆= 10^-2.16^+0.10_-0.12 Mpc-3 and L^⋆= 10^41.38^+0.07_-0.06 erg s-1 for [O III], and φ ^⋆= 10^-1.97^+0.07_-0.07 Mpc-3 and L^⋆= 10^41.66^+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 >1042 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 AHα = 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 log10ρSFR/(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.
Harish, S., Coughlin, A., Rhoads, J. E., Malhotra, S., Finkelstein, S. L., Stevans, M., Tilvi, V. S., Khostovan, A. A., Veilleux, S., Wang, J., Hibon, P., Zabl, J., Joshi, B., Pharo, J., Wold, I., Perez, L. A., Zheng, Z.-Y., Probst, R., Swaters, R., … Yang, H. (2020). A Comprehensive Study of H\ensuremathα Emitters at z \ensuremath∼ 0.62 in the DAWN Survey: The Need for Deep and Wide Regions. ApJ, 892(1), 30. https://doi.org/10.3847/1538-4357/ab7015
2019
Khostovan, A. A., Sobral, D., Mobasher, B., Matthee, J., Cochrane, R. K., Chartab, N., Jafariyazani, M., Paulino-Afonso, A., Santos, S., & Calhau, J. (2019). The clustering of typical Lyα emitters from z ∼2.5-6: host halo masses depend on Lyαand UV luminosities. MNRAS, 489, 555K.
We investigate the clustering and halo properties of ∼5000 Ly α-selected emission-line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between z ∼ 2.5 and 6. We measure clustering lengths of r0 ∼ 3-6 h-1 Mpc and typical halo masses of ∼1011 M⊙ for our narrowband-selected LAEs with typical LLy α ∼ 1042-43 erg s-1. The intermediate-band-selected LAEs are observed to have r0 ∼ 3.5-15 h-1 Mpc with typical halo masses of ∼1011-12 M⊙ and typical LLy α ∼ 1043-43.6 erg s-1. We find a strong, redshift-independent correlation between halo mass and Ly α luminosity normalized by the characteristic Ly α luminosity, L⋆(z). The faintest LAEs (L ∼ 0.1 L⋆(z)) typically identified by deep narrowband surveys are found in 1010 M⊙ haloes and the brightest LAEs (L ∼ 7 L⋆(z)) are found in ∼5 × 1012 M⊙ haloes. A dependency on the rest-frame 1500 Å UV luminosity, MUV, is also observed where the halo masses increase from 1011 to 1013 M⊙ for MUV ∼ -19 to -23.5 mag. Halo mass is also observed to increase from 109.8 to 1012 M⊙ for dust-corrected UV star formation rates from ∼0.6 to 10 M⊙ yr-1 and continues to increase up to 1013 M⊙ in halo mass, where the majority of those sources are active galactic nuclei. All the trends we observe are found to be redshift independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe.
Jafariyazani, M., Mobasher, B., Hemmati, S., Fetherolf, T., Khostovan, A. A., & Chartab, N. (2019). Spatially Resolved Properties of Galaxies from CANDELS+MUSE: Radial Extinction Profile and Insights on Quenching. ApJ, 887(2), 204. https://doi.org/10.3847/1538-4357/ab5526
Hu, W., Wang, J., Zheng, Z.-Y., Malhotra, S., Rhoads, J. E., Infante, L., Barrientos, L. F., Yang, H., Jiang, C., Kang, W., Perez, L. A., Wold, I., Hibon, P., Jiang, L., Khostovan, A. A., Valdes, F., Walker, A. R., Galaz, G., Coughlin, A., … Zheng, X. Z. (2019). The Ly\ensuremathα Luminosity Function and Cosmic Reionization at z \ensuremath∼ 7.0: A Tale of Two LAGER Fields. ApJ, 886(2), 90. https://doi.org/10.3847/1538-4357/ab4cf4
Zheng, Z.-Y., Rhoads, J. E., Wang, J.-X., Malhotra, S., Walker, A., Mooney, T., Jiang, C., Hu, W., Hibon, P., Jiang, L., Infante, L., Barrientos, L. F., Galaz, G., Valdes, F., Wester, W., Yang, H., Coughlin, A., Harish, S., Kang, W., … Zheng, X. Z. (2019). Design for the First Narrowband Filter for the Dark Energy Camera: Optimizing the LAGER Survey for z \ensuremath∼ 7 Galaxies. PASP, 131(1001), 074502. https://doi.org/10.1088/1538-3873/ab1c32
2018
Khostovan, A. A., Sobral, D., Mobasher, B., Best, P. N., Smail, I., Matthee, J., Darvish, B., Nayyeri, H., Hemmati, S., & Stott, J. P. (2018). The clustering of Hβ+ [OIII] and [OII] emitters since z ∼5: dependencies with line luminosity and stellar mass. MNRAS, 478, 2999K.
We investigate the clustering properties of ∼7000 H β + [O III] and [O II] narrowband-selected emitters at z ∼ 0.8-4.7 from the High-z Emission Line Survey. We find clustering lengths, r0, of 1.5-4.0 h-1 Mpc and minimum dark matter halo masses of 1010.7-12.1 M⊙ for our z = 0.8-3.2 H β + [O III] emitters and r0 ∼ 2.0-8.3 h-1 Mpc and halo masses of 1011.5-12.6 M⊙ for our z = 1.5-4.7 [O II] emitters. We find r0 to strongly increase both with increasing line luminosity and redshift. By taking into account the evolution of the characteristic line luminosity, L⋆(z), and using our model predictions of halo mass given r0, we find a strong, redshift-independent increasing trend between L/L⋆(z) and minimum halo mass. The faintest H β + [O III] emitters are found to reside in 109.5 M⊙ haloes and the brightest emitters in 1013.0 M⊙ haloes. For [O II] emitters, the faintest emitters are found in 1010.5 M⊙ haloes and the brightest emitters in 1012.6 M⊙ haloes. A redshift-independent stellar mass dependency is also observed where the halo mass increases from 1011 to 1012.5 M⊙ for stellar masses of 108.5 to 1011.5 M⊙, respectively. We investigate the interdependencies of these trends by repeating our analysis in a Lline-Mstar grid space for our most populated samples (H β + [O III] z = 0.84 and [O II] z = 1.47) and find that the line luminosity dependency is stronger than the stellar mass dependency on halo mass. For L > L⋆ emitters at all epochs, we find a relatively flat trend with halo masses of 1012.5-13 M⊙, which may be due to quenching mechanisms in massive haloes that is consistent with a transitional halo mass predicted by models.
Sobral, D., Santos, S., Matthee, J., Paulino-Afonso, A., Ribeiro, B., Calhau, J., & Khostovan, A. A. (2018). Slicing COSMOS with SC4K: the evolution of typical Ly \ensuremathα emitters and the Ly \ensuremathα escape fraction from z \ensuremath∼ 2 to 6. MNRAS, 476(4), 4725–4752. https://doi.org/10.1093/mnras/sty378
2017
Suzuki, T. L., Kodama, T., Onodera, M., Shimakawa, R., Hayashi, M., Tadaki, K.-ichi, Koyama, Y., Tanaka, I., Sobral, D., Smail, I., Best, P. N., Khostovan, A. A., Minowa, Y., & Yamamoto, M. (2017). The Interstellar Medium in [O III]-selected Star-forming Galaxies at z \ensuremath∼ 3.2. ApJ, 849(1), 39. https://doi.org/10.3847/1538-4357/aa8df3
Matthee, J., Sobral, D., Best, P., Khostovan, A. A., Oteo, I., Bouwens, R., & Röttgering, H. (2017). The production and escape of Lyman-Continuum radiation from star-forming galaxies at z \ensuremath∼ 2 and their redshift evolution. MNRAS, 465(3), 3637–3655. https://doi.org/10.1093/mnras/stw2973
Nayyeri, H., Hemmati, S., Mobasher, B., Ferguson, H. C., Cooray, A., Barro, G., Faber, S. M., Dickinson, M., Koekemoer, A. M., Peth, M., Salvato, M., Ashby, M. L. N., Darvish, B., Donley, J., Durbin, M., Finkelstein, S., Fontana, A., Grogin, N. A., Gruetzbauch, R., … Yan, H. (2017). CANDELS Multi-wavelength Catalogs: Source Identification and Photometry in the CANDELS COSMOS Survey Field. ApJS, 228(1), 7. https://doi.org/10.3847/1538-4365/228/1/7
2016
Khostovan, A. A., Sobral, D., Mobasher, B., Smail, I., Darvish, B., Nayyeri, H., Hemmati, S., & Stott, J. P. (2016). The nature of Hβ+[OIII] and [OII] emitters to z ∼5 with HiZELS: stellar mass functions and the evolution of EWs. MNRAS, 463, 2363K.
We investigate the properties of ∼7000 narrow-band selected galaxies with strong Hβ+[O III] and [O II] nebular emission lines from the High-z Emission-Line Survey between z ∼ 0.8 and 5.0. Our sample covers a wide range in stellar mass (Mstellar ∼ 107.5-12.0 M⊙), rest-frame equivalent widths (EWrest∼10-105 Å), and line luminosities (Lline ∼ 1040.5-43.2 erg s-1). We measure the Hβ+[O III]-selected stellar mass functions out to z ∼ 3.5 and find that both M⋆ and φ⋆ increases with cosmic time. The [O II]-selected stellar mass functions show a constant M⋆ ≈ 1011.6 M⊙ and a strong, increasing evolution with cosmic time in φ⋆ in line with Hα studies. We also investigate the evolution of the EWrest as a function of redshift with a fixed mass range (109.5-10.0 M⊙) and find an increasing trend best represented by (1 + z)3.81 ± 0.14 and (1 + z)2.72 ± 0.19 up to z ∼ 2 and ∼3 for Hβ+[O III] and [O II] emitters, respectively. This is the first time that the EWrest evolution has been directly measured for Hβ+[O III] and [O II] emitters up to these redshifts. There is evidence for a slower evolution for z > 2 in the Hβ+[O III] EWrest and a decreasing trend for z > 3 in the [O II] EWrest evolution, which would imply low [O II] EW at the highest redshifts and higher [O III]/[O II] line ratios. This suggests that the ionization parameter at higher redshift may be significantly higher than the local Universe. Our results set the stage for future near-IR space-based spectroscopic surveys to test our extrapolated predictions and also produce z > 5 measurements to constrain the high-z end of the EWrest and [O III]/[O II] evolution.
Suzuki, T. L., Kodama, T., Sobral, D., Khostovan, A. A., Hayashi, M., Shimakawa, R., Koyama, Y., Tadaki, K.-i., Tanaka, I., Minowa, Y., Yamamoto, M., Smail, I., & Best, P. N. (2016). [O III] emission line as a tracer of star-forming galaxies at high redshifts: comparison between H\ensuremathα and [O III] emitters at z=2.23 in HiZELS. MNRAS, 462(1), 181–189. https://doi.org/10.1093/mnras/stw1655
2015
Khostovan, A. A., Sobral, D., Mobasher, B., Best, P. N., Smail, I., Stott, J. P., Hemmati, S., & Nayyeri, H. (2015). Evolution of the Hβ+ [OIII] and [OII] luminosity functions and the [OII] star formation history of the Universe up to z ∼5 from HiZELS. MNRAS, 452, 3948K.
We investigate the evolution of the H β + [O III] and [O II] luminosity functions from z ∼ 0.8 to ∼5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). This is the first time that the H β + [O III] and [O II] luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of [O II] and H β + [O III] emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ∼1 × 106 Mpc-3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour-colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L⋆ and a decrease in φ⋆ for both H β + [O III] and [O II] emitters. We derive the [O II] star formation history of the Universe since z ∼ 5 and find that the cosmic star formation rate density (SFRD) rises from z ∼ 5 to ∼3 and then drops towards z ∼ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ∼ 5 based only on a single tracer of star formation. When comparing the H β + [O III] SFRDs to the [O II] and H α SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the H β + [O III] sample is dominated by star-forming galaxies at high-z rather than AGNs.
Sobral, D., Matthee, J., Best, P. N., Smail, I., Khostovan, A. A., Milvang-Jensen, B., Kim, J.-W., Stott, J., Calhau, J., Nayyeri, H., & Mobasher, B. (2015). CF-HiZELS, an \ensuremath∼10 deg^2 emission-line survey with spectroscopic follow-up: H\ensuremathα, [O III] + H\ensuremathβ and [O II] luminosity functions at z = 0.8, 1.4 and 2.2. MNRAS, 451(3), 2303–2323. https://doi.org/10.1093/mnras/stv1076
2014
2013
2012
Kim, S., Wardlow, J. L., Cooray, A., Fleuren, S., Sutherland, W., Khostovan, A. A., Auld, R., Baes, M., Bussmann, R. S., Buttiglione, S., Cava, A., Clements, D., Dariush, A., De Zotti, G., Dunne, L., Dye, S., Eales, S., Fritz, J., Hopwood, R., … van der Werf, P. (2012). SPITZER-IRAC Identification of HERSCHEL-ATLAS SPIRE Sources. ApJ, 756(1), 28. https://doi.org/10.1088/0004-637X/756/1/28
2011
Koekemoer, A. M., Faber, S. M., Ferguson, H. C., Grogin, N. A., Kocevski, D. D., Koo, D. C., Lai, K., Lotz, J. M., Lucas, R. A., McGrath, E. J., Ogaz, S., Rajan, A., Riess, A. G., Rodney, S. A., Strolger, L., Casertano, S., Castellano, M., Dahlen, T., Dickinson, M., … Yun, M. S. (2011). CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey—The Hubble Space Telescope Observations, Imaging Data Products, and Mosaics. ApJS, 197(2), 36. https://doi.org/10.1088/0067-0049/197/2/36
Amblard, A., Cooray, A., Serra, P., Altieri, B., Arumugam, V., Aussel, H., Blain, A., Bock, J., Boselli, A., Buat, V., Castro-Rodrı́guez N., Cava, A., Chanial, P., Chapin, E., Clements, D. L., Conley, A., Conversi, L., Dowell, C. D., Dwek, E., … Zemcov, M. (2011). Submillimetre galaxies reside in dark matter haloes with masses greater than 3\texttimes10^11 solar masses. Nature, 470(7335), 510–512. https://doi.org/10.1038/nature09771
Hopwood, R., Wardlow, J., Cooray, A., Khostovan, A. A., Kim, S., Negrello, M., da Cunha, E., Burgarella, D., Aretxaga, I., Auld, R., Baes, M., Barton, E., Bertoldi, F., Bonfield, D. G., Blundell, R., Buttiglione, S., Cava, A., Clements, D. L., Cooke, J., … Vieira, J. D. (2011). Spitzer Imaging of Herschel-atlas Gravitationally Lensed Submillimeter Sources. ApJL, 728(1), L4. https://doi.org/10.1088/2041-8205/728/1/L4
2010
Cooray, A., Amblard, A., Wang, L., Arumugam, V., Auld, R., Aussel, H., Babbedge, T., Blain, A., Bock, J., Boselli, A., Buat, V., Burgarella, D., Castro-Rodriguez, N., Cava, A., Chanial, P., Clements, D. L., Conley, A., Conversi, L., Dowell, C. D., … Zemcov, M. (2010). HerMES: Halo occupation number and bias properties of dusty galaxies from angular clustering measurements. A&A, 518, L22. https://doi.org/10.1051/0004-6361/201014597
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