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arXiv · 2503.00120

COSMOS Spectroscopic Redshift Compilation (First Data Release): 488k Redshifts Encompassing Two Decades of Spectroscopy

Ali Ahmad Khostovan·Jeyhan S. Kartaltepe·Mara Salvato·Olivier Ilbert·Caitlin M. Casey·Hiddo Algera·Jacqueline Antwi-Danso·Andrew Battisti·Malte Brinch·Marcella Brusa·Antonello Calabro·Peter L. Capak·Nima Chartab·Olivia R. Cooper·Isa G. Cox·Behnam Darvish·Nicole E. Drakos·Andreas L. Faisst·Matthew R. George·Ghassem Gozaliasl·Santosh Harish·Gunther Hasinger·Hossein Hatamnia·Angela Iovino·Shuowen Jin·Daichi Kashino·Anton M. Koekemoer·Ronaldo Laishram·Khee-Gan Lee·Jitrapon Lertprasertpong·Simon J. Lilly·Daizhong Liu·Daniel C. Masters·Bahram Mobasher·Tohru Nagao·Masato Onodera·Yingjie Peng·David B. Sanders·Ryan L. Sanders·Zahra Sattari·Nick Scoville·Ekta A. Shah·John D. Silverman·Nao Suzuki·Sina Taamoli·Masayuki Tanaka·Lidia A. M. Tasca·Sune Toft·Greta Toni·Benny Trakhtenbrot·Jonathan R. Trump·Mattia Vaccari·Francesco Valentino·Brittany N. Vanderhoof·John R. Weaver·Min S. Yun·Jorge A. Zavala
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Abstract

We present the COSMOS Spectroscopic Redshift Compilation encompassing ~ 20 years of spectroscopic redshifts within a 10 deg$^2$ area centered on the 2 deg$^2$ COSMOS legacy field. This compilation contains 487,666 redshifts of 266,284 unique objects from 138 individual observing programs up to $z \sim 8$ with median stellar mass $\sim 10^{8.4}$ to $10^{10}$ M$_\odot$ (redshift dependent). Rest-frame $NUVrJ$ colors and SFR -- stellar mass correlations show the compilation primarily contains low- to intermediate-mass star-forming and massive, quiescent galaxies at $z < 1.25$ and mostly low-mass bursty star-forming galaxies at $z > 2$. Sources in the compilation cover a diverse range of environments, including protoclusters such as ``Hyperion''. The full compilation is 50\% spectroscopically complete by $i \sim 23.4$ and $K_s \sim 21.6$ mag; however, this is redshift dependent. Spatially, the compilation is $>50$\% ($>30$\%) complete within the central (outer) region limited to $i < 24$ mag and $K_s < 22.5$ mag, separately. We demonstrate how the compilation can be used to validate photometric redshifts and investigate calibration metrics. By training self-organizing maps on COSMOS2020/Classic and projecting the compilation onto it, we find key galaxy subpopulations that currently lack spectroscopic coverage including $z < 1$ intermediate-mass quiescent galaxies and low-/intermediate-mass bursty star-forming galaxies, $z \sim 2$ massive quiescent galaxies, and $z > 3$ massive star-forming galaxies. This highlights how combining self-organizing maps with our compilation can provide guidance for future spectroscopic observations to get a complete spectroscopic view of galaxy populations. Lastly, the compilation will undergo periodic data releases that incorporate new spectroscopic redshift measurements, providing a lasting legacy resource for the community.

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Ali Ahmad Khostovan, Jeyhan S. Kartaltepe, Mara Salvato, Olivier Ilbert, Caitlin M. Casey, Hiddo Algera, Jacqueline Antwi-Danso, Andrew Battisti, Malte Brinch, Marcella Brusa, Antonello Calabro, Peter L. Capak, Nima Chartab, Olivia R. Cooper, Isa G. Cox, Behnam Darvish, Nicole E. Drakos, Andreas L. Faisst, Matthew R. George, Ghassem Gozaliasl, Santosh Harish, Gunther Hasinger, Hossein Hatamnia, Angela Iovino, Shuowen Jin, Daichi Kashino, Anton M. Koekemoer, Ronaldo Laishram, Khee-Gan Lee, Jitrapon Lertprasertpong, Simon J. Lilly, Daizhong Liu, Daniel C. Masters, Bahram Mobasher, Tohru Nagao, Masato Onodera, Yingjie Peng, David B. Sanders, Ryan L. Sanders, Zahra Sattari, Nick Scoville, Ekta A. Shah, John D. Silverman, Nao Suzuki, Sina Taamoli, Masayuki Tanaka, Lidia A. M. Tasca, Sune Toft, Greta Toni, Benny Trakhtenbrot, Jonathan R. Trump, Mattia Vaccari, Francesco Valentino, Brittany N. Vanderhoof, John R. Weaver, Min S. Yun, Jorge A. Zavala. 2025-10-29. COSMOS Spectroscopic Redshift Compilation (First Data Release): 488k Redshifts Encompassing Two Decades of Spectroscopy. https://arxiv.org/abs/2503.00120

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