J/ApJ/920/105 117 star clusters in poststarburst galaxy S12 (Chandar+, 2021)
The Star Formation History of a Post-starburst Galaxy Determined from Its
Cluster Population.
Chandar R., Mok A., French K.D., Smercina A., Smith J.-D.T.
<Astrophys. J., 920, 105 (2021)>
=2021ApJ...920..105C 2021ApJ...920..105C
ADC_Keywords: Galaxies; Clusters, open; Photometry, UBVRI
Keywords: Galaxy formation
Abstract:
The recent star formation histories (SFHs) of post-starburst galaxies
have been determined almost exclusively from detailed modeling of
their composite starlight. This has provided important but limited
information on the number, strength, and duration of bursts of star
formation. In this work, we present a direct and independent measure
of the recent SFH of the post-starburst galaxy S12 (plate-mjd-fiber
for SDSS623-52051-207; designated EAS12 in Smercina et al.) from its
star cluster population. We detect clusters from high-resolution, UBR
optical images taken with the Hubble Space Telescope and compare their
luminosities and colors with stellar population models to estimate the
ages and masses of the clusters. No clusters younger than ∼70Myr are
found, indicating star formation shut off at this time. Clusters
formed ∼120Myr ago reach masses up to a ∼fewx107M☉, several times
higher than similar-age counterparts formed in actively merging
galaxies like the Antennae and NGC3256. We develop a new calibration
based on known properties for eight nearby galaxies to estimate the
star formation rate (SFR) of a galaxy from the mass of the most
massive cluster, Mmax. The cluster population indicates that S12
experienced an extremely intense but short-lived burst ∼120Myr ago,
with an estimated peak of 500-250+500M☉/yr and duration of
50±25Myr, one of the highest SFRs estimated for any galaxy in the
modern universe. The cluster population also allows us to fill in more
of the backstory of S12. Prior to the recent, intense burst, S12 was
forming stars at a moderate rate of ∼3-5M☉/yr, typical of spiral
galaxies, but the system experienced an earlier burst at some point,
approximately 1-3Gyr ago. While fairly uncertain, we estimate that the
SFR during this earlier burst was ∼20-30M☉/yr, similar to the
current SFR in the Antennae and NGC3256.
Description:
We downloaded the reduced WFC3/UVIS images in the U, B, and R bands
from the Hubble Legacy Archive, which corrects each exposure for dark
current and bias, then flat-fields and drizzles them together through
the standard WFC3 pipeline to a scale of 0.04"/pix.
Objects:
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RA (ICRS) DE Designation(s)
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16 13 32.22 +51 03 43.0 SDSS 6316-56483-722 = 2MASX J16133219+5103436
16 13 30.18 +51 03 35.6 SDSS 623-52051-207 = 2MASX J16133017+5103356
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 66 117 *Catalog of Star Clusters in Poststarburst Galaxy S12
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Note on table2.dat : plate-mjd-fiber for SDSS 623-52051-207 from
Smercina+, 2018ApJ...855...51S 2018ApJ...855...51S as designated EAS12 in Decker
French+, 2015ApJ...801....1D 2015ApJ...801....1D.
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)
J/AJ/140/75 : Antennae galaxies (NGC 4038/4039) revisited (Whitmore+, 2010)
J/ApJ/741/86 : XRBs and star clusters in NGC 4449 (Rangelov+, 2011)
J/ApJ/826/32 : HST observations of star clusters in NGC 3256 (Mulia+, 2016)
J/ApJ/862/2 : Post-starburst galaxy ages from SDSS (French+, 2018)
J/ApJ/889/154 : LEGUS & Ha-LEGUS obs of NGC4449 star clusters (Whitmore+, 2020)
http://hla.stsci.edu/ : Hubble Legacy Archive
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/117] Sequential Source ID
5- 14 F10.6 deg RAdeg [243/244] Right Ascension (J2000)
16- 25 F10.7 deg DEdeg [51/52] Declination (J2000)
27- 34 F8.3 mag Umag [20.2/30.6]?=-999.000 WFPC3 HST/UVIS F336W
Vega-calibrated magnitude (1)
36- 40 F5.3 mag e_Umag [0.01/0.7] Uncertainty in Umag
42- 47 F6.3 mag Bmag [20.7/30.4] WFPC3 HST/UVIS F438W
Vega-calibrated magnitude (1)
49- 53 F5.3 mag e_Bmag [0.01/0.2] Uncertainty in Bmag
55- 60 F6.3 mag Rmag [20.3/27.3] WFPC3 HST/UVIS F625W Vega-calibrated
magnitude (1)
62- 66 F5.3 mag e_Rmag [0.009/0.05] Uncertainty in Rmag
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Note (1): Instrumental magnitudes are converted to the VEGAMAG system by
applying the following zeropoints from the WFC3 data handbook to our
measured photometry: 23.46 (U), 24.98 (B), and 25.37 (R) mag.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 13-Feb-2024