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Searching for the lowest metallicity galaxies in the local universe (2018)
Journal Article
Hsyu, T., Cooke, R. J., Prochaska, J. X., & Bolte, M. (2018). Searching for the lowest metallicity galaxies in the local universe. Astrophysical Journal, 863(2), Article 134. https://doi.org/10.3847/1538-4357/aad18a

We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3 m Lick Observatory and 10 m W.M. Keck Observatory optical spectroscopic observations o... Read More about Searching for the lowest metallicity galaxies in the local universe.

One Percent Determination of the Primordial Deuterium Abundance (2018)
Journal Article
Cooke, R. J., Pettini, M., & Steidel, C. C. (2018). One Percent Determination of the Primordial Deuterium Abundance. Astrophysical Journal, 855(2), Article 102. https://doi.org/10.3847/1538-4357/aaab53

We report a reanalysis of a near-pristine absorption system, located at a redshift ${z}_{\mathrm{abs}}=2.52564$ toward the quasar Q1243+307, based on the combination of archival and new data obtained with the HIRES echelle spectrograph on the Keck te... Read More about One Percent Determination of the Primordial Deuterium Abundance.

Origins of carbon-enhanced metal-poor stars (2017)
Journal Article
Sharma, M., Theuns, T., Frenk, C. S., & Cooke, R. J. (2018). Origins of carbon-enhanced metal-poor stars. Monthly Notices of the Royal Astronomical Society, 473(1), 984-995. https://doi.org/10.1093/mnras/stx2392

We investigate the nature of carbon-enhanced metal-poor (CEMP) stars in Milky Way (MW) analogues selected from the EAGLE cosmological hydrodynamical simulation. The stellar evolution model in EAGLE includes the physics of enrichment by asymptotic gia... Read More about Origins of carbon-enhanced metal-poor stars.

The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe (2017)
Journal Article
Hsyu, T., Cooke, R. J., Prochaska, J. X., & Bolte, M. (2017). The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe. Astrophysical Journal, 845(2), Article L22. https://doi.org/10.3847/2041-8213/aa821f

We report the discovery of the Little Cub, an extremely metal-poor star-forming galaxy in the local universe, found in the constellation Ursa Major (a.k.a. the Great Bear). We first identified the Little Cub as a candidate metal-poor galaxy based on... Read More about The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe.

Discovery of the most metal-poor damped Lyman-α system (2017)
Journal Article
Cooke, R. J., Pettini, M., & Steidel, C. C. (2017). Discovery of the most metal-poor damped Lyman-α system. Monthly Notices of the Royal Astronomical Society, 467(1), 802-811. https://doi.org/10.1093/mnras/stx037

We report the discovery and analysis of the most metal-poor damped Lyman α (DLA) system currently known, based on observations made with the Keck HIRES spectrograph. The metal paucity of this system has only permitted the determination of three eleme... Read More about Discovery of the most metal-poor damped Lyman-α system.

The primordial abundance of deuterium: ionization correction (2016)
Journal Article
Cooke, R., & Pettini, M. (2016). The primordial abundance of deuterium: ionization correction. Monthly Notices of the Royal Astronomical Society, 455(2), 1512-1521. https://doi.org/10.1093/mnras/stv2343

We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman α (DLA) and sub-DLA systems using a detailed suite of photoionization simulations. We model metal-poor DLAs as clouds of gas in pressure equilibrium with a... Read More about The primordial abundance of deuterium: ionization correction.

The Primordial Deuterium Abundance of the Most Metal-poor Damped Lyman-alpha System (2016)
Journal Article
Cooke, R., Pettini, M., Nollett, K., & Jorgenson, R. (2016). The Primordial Deuterium Abundance of the Most Metal-poor Damped Lyman-alpha System. Astrophysical Journal, 830(2), Article 148. https://doi.org/10.3847/0004-637x/830/2/148

We report the discovery and analysis of the most metal-poor damped Lyman-alpha (DLA) system currently known, which also displays the Lyman series absorption lines of neutral deuterium. The average [O/H] abundance of this system is [O/H] = -2.804 +/-... Read More about The Primordial Deuterium Abundance of the Most Metal-poor Damped Lyman-alpha System.

Discovery of a Damped Ly-alpha Absorber at z = 3.3 along a Galaxy Sight-line in the SSA22 Field (2016)
Journal Article
Mawatari, K., Inoue, A., Kousai, K., Hayashino, T., Cooke, R., Prochaska, J., …Matsuda, Y. (2016). Discovery of a Damped Ly-alpha Absorber at z = 3.3 along a Galaxy Sight-line in the SSA22 Field. Astrophysical Journal, 817(2), Article 161. https://doi.org/10.3847/0004-637x/817/2/161

Using galaxies as background light sources to map the Lya absorption lines is a novel approach to study Damped Lya Absorbers (DLAs). We report the discovery of an intervening z = 3.335 +- 0.007 DLA along a galaxy sight-line identified among 80 Lyman... Read More about Discovery of a Damped Ly-alpha Absorber at z = 3.3 along a Galaxy Sight-line in the SSA22 Field.

Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-Ray Bursts (2015)
Journal Article
Cucchiara, A., Fumagalli, M., Rafelski, M., Kocevski, D., Prochaska, J., Cooke, R., & Becker, G. (2015). Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-Ray Bursts. Astrophysical Journal, 804(1), https://doi.org/10.1088/0004-637x/804/1/51

We present the largest, publicly available sample of damped Lyα systems (DLAs) along the lines of sight of Swift-discovered gamma-ray bursts (GRBs) in order to investigate the environmental properties of long GRB hosts in the z = 1.8–6 redshift range... Read More about Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-Ray Bursts.

The most metal-poor damped Lyα systems: An insight into dwarf galaxies at high redshift (2015)
Journal Article
Cooke, R., Pettini, M., & Jorgenson, R. (2015). The most metal-poor damped Lyα systems: An insight into dwarf galaxies at high redshift. Astrophysical Journal, 800(1), Article 12. https://doi.org/10.1088/0004-637x/800/1/12

In this paper we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyα systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a... Read More about The most metal-poor damped Lyα systems: An insight into dwarf galaxies at high redshift.

The cold veil of the Milky Way stellar halo (2012)
Journal Article
Deason, A., Belokurov, V., Evans, N., Koposov, S., Cooke, R., Peñarrubia, J., …Olszewski, E. (2012). The cold veil of the Milky Way stellar halo. Monthly Notices of the Royal Astronomical Society, 425(4), 2840-2853. https://doi.org/10.1111/j.1365-2966.2012.21639.x

We build a sample of distant (D > 80 kpc) stellar halo stars with measured radial velocities. Faint (20 < g < 22) candidate blue horizontal branch (BHB) stars were selected using the deep, but wide, multi-epoch Sloan Digital Sky Survey photometry. Fo... Read More about The cold veil of the Milky Way stellar halo.

The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime (2011)
Journal Article
Cooke, R., Pettini, M., Steidel, C., Rudie, G., & Nissen, P. (2011). The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime. Monthly Notices of the Royal Astronomical Society, 417(2), 1534-1558. https://doi.org/10.1111/j.1365-2966.2011.19365.x

We present a high spectral resolution survey of the most metal-poor damped Lyα absorption systems (DLAs) aimed at probing the nature and nucleosynthesis of the earliest generations of stars. Our survey comprises 22 systems with iron abundance less th... Read More about The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime.