TY - JOUR

T1 - REQUIEM-2D

T2 - A Diversity of Formation Pathways in a Sample of Spatially Resolved Massive Quiescent Galaxies at z similar to 2

AU - Akhshik, Mohammad

AU - Whitaker, Katherine E.

AU - Leja, Joel

AU - Richard, Johan

AU - Spilker, Justin S.

AU - Song, Mimi

AU - Brammer, Gabriel

AU - Bezanson, Rachel

AU - Ebeling, Harald

AU - Gallazzi, Anna R.

AU - Mahler, Guillaume

AU - Mowla, Lamiya A.

AU - Nelson, Erica J.

AU - Pacifici, Camilla

AU - Sharon, Keren

AU - Toft, Sune

AU - Williams, Christina C.

AU - Wright, Lillian

AU - Zabl, Johannes

PY - 2023/2/1

Y1 - 2023/2/1

N2 - REQUIEM-2D (Resolving Quiescent Magnified Galaxies with 2D Grism Spectroscopy) comprises a sample of eight massive (log(M-* /M-circle dot) > 10.6) strongly lensed quiescent galaxies at z similar to 2. REQUIEM-2D combines the natural magnification from strong gravitational lensing with the high-spatial-resolution grism spectroscopy of the Hubble Space Telescope through a spectrophotometric fit to study spatially resolved stellar populations. We show that quiescent galaxies in the REQUIEM-2D survey have diverse formation histories with age gradients at the 1 sigma- 3 sigma level, including examples of (1) a younger central region supporting outside-in formation, (2) flat age gradients that show evidence for both spatially uniform early formation and inside-out quenching, and (3) regions at a fixed radial distance having different ages (such asymmetries cannot be recovered when averaging stellar population measurements azimuthally). The typical dust attenuation curve for the REQUIEM-2D galaxies is constrained to be steeper than Calzetti's law in the UV and generally consistent with A(V) < 1. Combined together and accounting for the different physical radial distances and formation timescales, we find that the REQUIEM-2D galaxies that formed earlier in the universe exhibit slow and uniform growth in their inner core, whereas the galaxies that formed later have rapid inner growth in their inner core with younger ages than the outskirts. These results challenge the currently accepted paradigm of how massive quiescent galaxies form, where the earliest galaxies are thought to form most rapidly. Significantly larger samples close to the epoch of formation with similar data quality and higher spectral resolution are required to validate this finding.

AB - REQUIEM-2D (Resolving Quiescent Magnified Galaxies with 2D Grism Spectroscopy) comprises a sample of eight massive (log(M-* /M-circle dot) > 10.6) strongly lensed quiescent galaxies at z similar to 2. REQUIEM-2D combines the natural magnification from strong gravitational lensing with the high-spatial-resolution grism spectroscopy of the Hubble Space Telescope through a spectrophotometric fit to study spatially resolved stellar populations. We show that quiescent galaxies in the REQUIEM-2D survey have diverse formation histories with age gradients at the 1 sigma- 3 sigma level, including examples of (1) a younger central region supporting outside-in formation, (2) flat age gradients that show evidence for both spatially uniform early formation and inside-out quenching, and (3) regions at a fixed radial distance having different ages (such asymmetries cannot be recovered when averaging stellar population measurements azimuthally). The typical dust attenuation curve for the REQUIEM-2D galaxies is constrained to be steeper than Calzetti's law in the UV and generally consistent with A(V) < 1. Combined together and accounting for the different physical radial distances and formation timescales, we find that the REQUIEM-2D galaxies that formed earlier in the universe exhibit slow and uniform growth in their inner core, whereas the galaxies that formed later have rapid inner growth in their inner core with younger ages than the outskirts. These results challenge the currently accepted paradigm of how massive quiescent galaxies form, where the earliest galaxies are thought to form most rapidly. Significantly larger samples close to the epoch of formation with similar data quality and higher spectral resolution are required to validate this finding.

KW - STAR-FORMATION HISTORIES

KW - MOLECULAR GAS CONTENT

KW - STELLAR POPULATIONS

KW - PHOTOMETRIC CATALOGS

KW - PHYSICAL-PROPERTIES

KW - ILLUSTRIS PROJECT

KW - FORMING GALAXIES

KW - DEAD GALAXIES

KW - SPECTROSCOPY

KW - EVOLUTION

U2 - 10.3847/1538-4357/aca677

DO - 10.3847/1538-4357/aca677

M3 - Journal article

VL - 943

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 179

ER -