What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST
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What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST. / Faisst, Andreas L. L.; Chary, Ranga Ram; Brammer, Gabriel; Toft, Sune.
In: Astrophysical Journal Letters, Vol. 941, No. 1, L11, 10.12.2022.Research output: Contribution to journal › Letter › Research › peer-review
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TY - JOUR
T1 - What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST
AU - Faisst, Andreas L. L.
AU - Chary, Ranga Ram
AU - Brammer, Gabriel
AU - Toft, Sune
PY - 2022/12/10
Y1 - 2022/12/10
N2 - We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1-5 mu m to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3-7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are > 3 mag fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50 pc. This is significantly smaller than star-forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2-0.3 Z(? )and ages of 1.5(-0.5)(+0.5)Gyr Z(?) and solar/supersolar at 4 sigma significance. Assuming mass-to-light ratios obtained from the best-fit SSP, we estimate stellar masses of 2.4(-1.5)(+3.0)x10(6)M(? )z = 0.5-0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.
AB - We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1-5 mu m to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3-7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are > 3 mag fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50 pc. This is significantly smaller than star-forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2-0.3 Z(? )and ages of 1.5(-0.5)(+0.5)Gyr Z(?) and solar/supersolar at 4 sigma significance. Assuming mass-to-light ratios obtained from the best-fit SSP, we estimate stellar masses of 2.4(-1.5)(+3.0)x10(6)M(? )z = 0.5-0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.
KW - STELLAR POPULATION SYNTHESIS
KW - GLOBULAR-CLUSTERS
KW - EVOLUTIONARY SYNTHESIS
KW - FORMATION EFFICIENCIES
KW - ILLUSTRIS PROJECT
KW - ASSEMBLY HISTORY
KW - DWARF GALAXIES
KW - COSMOS FIELD
KW - MASS
KW - SYSTEMS
U2 - 10.3847/2041-8213/aca1bf
DO - 10.3847/2041-8213/aca1bf
M3 - Letter
VL - 941
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
SN - 2041-8205
IS - 1
M1 - L11
ER -
ID: 330778244