J/ApJS/275/5 Scylla. I. HST obs. of ULLYSES fields in LMC & SMC (Murray+, 2024)
Scylla.
I. A pure-parallel, multiwavelength imaging survey of the ULLYSES fields
in the LMC and SMC.
Murray C.E., Lindberg C.W., Yanchulova Merica-Jones P., Williams B.F.,
Cohen R.E., Gordon K.D., McQuinn K.B.W., Choi Y., Burhenne C.,
Sandstrom K.M., Bot C., Johnson L.C., Goldman S.R., Clark C.J.R.,
Roman-Duval J.C., Gilbert K.M., Peek J.E.G., Hirschauer A.S., Boyer M.L.,
Dolphin A.E.
<Astrophys. J. Suppl. Ser., 275, 5 (2024)>
=2024ApJS..275....5M 2024ApJS..275....5M
ADC_Keywords: Magellanic Clouds; Photometry, HST; Surveys; Magnitudes;
Interstellar medium; Infrared; Ultraviolet; Optical
Keywords: Magellanic Clouds ; Hubble Space Telescope ; Surveys ; Catalogs ;
Star formation ; Interstellar medium
Abstract:
Scylla is a deep Hubble Space Telescope (HST) survey of the stellar
populations, interstellar medium, and star formation in the LMC and
SMC. As a pure-parallel complement to the Ultraviolet Legacy Library
of Young Stars as Essential Standards (ULLYSES) survey, Scylla
obtained 342 orbits of ultraviolet (UV) through near-IR imaging of the
LMC and SMC with Wide Field Camera 3. In this paper, we describe the
science objectives, observing strategy, data reduction procedure, and
initial results from our photometric analysis of 96 observed fields.
Although our observations were constrained by ULLYSES primary
exposures, we imaged all fields in at least two filters (F475W and
F814W) and 64% of fields in at least three and as many as seven WFC3
filters spanning the UV to IR. Overall, we reach average 50%
completeness of mF225W=26.0, mF275W=26.2, mF336W=26.9,
mF475W=27.8, mF814W=25.5, mF110W=24.7, and mF160W=24.0 Vega
mag in our photometric catalogs, which is faintward of the ancient
main-sequence turnoff in all filters. The primary science goals of
Scylla include characterizing the structure and properties of dust in
the MCs, as well as their spatially resolved star formation and
chemical enrichment histories. Our images and photometric catalogs,
which represent the widest-area coverage of MCs with HST photometry to
date, are available as a high-level science product at the Barbara A.
Mikulski Archive for Space Telescopes.
Description:
We observed each Ultraviolet Legacy Library of Young Stars as
Essential Standards (ULLYSES; Roman-Duval 2020RNAAS...4..205R 2020RNAAS...4..205R)
parallel field with HST WFC3 in filters spanning UV, optical, and NIR
wavelengths.
In Figure 3, we summarize the positions and wavelength coverage of
Scylla imaging from this release (observations through 2023 February)
in the LMC and SMC. Scylla increases the total spatial coverage of
UV-IR imaging from HST by factors of 2 and 8 in the LMC and SMC,
respectively.
Assuming average distances to the LMC and SMC of 50 and 62kpc,
respectively, and a field of view of WFC3 UVIS of 160", each field
covers an area of ∼39(48)pc on a side in the LMC (SMC).
The Scylla survey's deep, multiwavelength imaging and photometric
catalog data products are available as an High Level Science Product
(HLSP) at MAST via doi:10.17909/mk54-kg51.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 53 96 Number of orbits per field
table5.dat 95 810 Observing parameters
table6.dat 62 735 Summary of artificial star tests (ASTs) for source
density-dominated fields
table7.dat 65 504 Summary of ASTs for background density-dominated
fields
table8.dat 58 96 Completeness
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See also:
II/375 : VISTA Magellanic Survey (VMC) catalog (YJKs) DR6 (Cioni+, 2011)
II/351 : VISTA Magellanic Survey (VMC) catalog (Cioni+, 2011)
J/PASP/110/863 : A Stellar Spectral Flux Library: 1150 - 25000 A (Pickles 1998)
J/ApJS/197/16 : CO observations of LMC molecular clouds (MAGMA). (Wong+, 2011)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJS/222/11 : Hubble Tarantula Treasury Project (HTTP). III. (Sabbi+, 2016)
J/ApJ/816/49 : Spitzer/IRAC observations of SMC Cepheids (Scowcroft+, 2016)
J/AJ/154/199 : SMASH: the MAgellanic Stellar History survey (Nidever+, 2017)
J/ApJ/871/151 : METAL Hubble program. I. Initial results (Roman-Duval+, 2019)
J/AJ/161/74 : SMASH DR2. 197 SMASH fields (Nidever+, 2021)
J/ApJS/253/53 : PHATTER. I. HST obs. of stars in M33 (Williams+, 2021)
http://archive.stsci.edu/hlsp/scylla : Scylla homepage on MAST
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Short Field Name (G1)
8- 30 A23 --- Field Long Field Name (G1)
32- 38 F7.4 deg RAdeg [9.5/86.6] Average Right Ascension (J2000)
40- 47 F8.4 deg DEdeg [-73.5/-65.5] Average Declination (J2000)
49- 49 I1 --- Nfilt [2/7] Number of filters used in the
field's observations
51- 51 I1 --- Norb [2/5] Number of orbits per field
53- 53 A1 --- Comb Filter Combinations; Table 1 (1)
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Note (1): Filter combinations, from Table 1 as follows:
A = F225W, F275W, F336W, F475W, F814W, F110W, F160W;
B = F275W, F336W, F475W, F814W, F110W, F160W;
C = F225W, F275W, F336W, F475W, F814W, F160W;
D = F275W, F336W, F475W, F814W, F160W;
E = F225W, F275W, F336W, F475W, F814W;
F = F336W, F475W, F814W, F160W;
G = F275W, F336W, F475W, F814W;
H = F336W, F475W, F814W;
I = F475W, F814W;
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Short Field Name (G1)
8- 30 A23 --- Field Long Field Name (G1)
32- 40 A9 --- Root Exposure identifier in MAST
42- 51 F10.7 deg RAdeg [9.5/86.6] Observation Right Ascension (J2000)
53- 62 F10.6 deg DEdeg [-73.5/-65.5] Observation Declination (J2000)
64- 71 F8.4 deg PA [24.5/349.5] Position Angle
73- 78 A6 --- Det Detector Name
80- 84 A5 --- Filt Filter
86- 91 F6.1 s Texp [3/1720] Exposure time
93- 95 F3.1 s pflash [0/8.3]? Post-flash level for the exposure
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 1 A1 --- l_Dens Limit on Source Density
3- 7 F5.3 ct.arcsec-2 b_Dens [0/2] Lower bound on Source density
9- 13 F5.3 ct.arcsec-2 B_Dens [0.27/2]? Upper bound on Source density
15- 19 A5 --- Filt Filter
21- 25 F5.2 mag mag [18.25/28.25] Vega magnitude in Filter
27- 31 F5.3 --- Comp [0.001/1]? Completeness (1)
33- 37 F5.3 --- e_Comp [0.001/0.3]? Uncertainty in Comp (1)
39- 44 F6.3 mag Bias [-3.32/2.8]? Bias, Vega magnitude (1)
46- 50 F5.3 mag e_Bias [0.001/0.9]? Uncertainty in Bias (1)
52- 56 F5.3 mag Unc [0/2]? Uncertainty, Vega magnitude (1)
58- 62 F5.3 mag e_Unc [0.001/0.7]? Uncertainty in Unc (1)
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Note (1): Null values correspond to cases where no measurement was
made. E.g., if there was no observation within a source density
range for a given filter within a certain flux bin, there is no
measurement of completeness, bias or uncertainty
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.3 ct.arcsec-2 b_Dens [0.006/37.1] Lower bound on Source density,
sources per arcsec^2
8- 16 F9.3 ct.arcsec-2 B_Dens [5.38/13555] Upper bound on Source density,
sources per arcsec^2
18- 22 A5 --- Filt Filter
24- 28 F5.2 mag mag [18.25/28.25] Vega magnitude in Filter
30- 34 F5.3 --- Comp [0.002/1]? Completeness (1)
36- 40 F5.3 --- e_Comp [0.001/0.4]? Uncertainty in Comp (1)
42- 47 F6.3 mag Bias [-3.4/2]? Bias, Vega magnitude (1)
49- 53 F5.3 mag e_Bias [0.001/1.4]? Uncertainty in Bias (1)
55- 59 F5.3 mag Unc [0/2.1]? Uncertainty, Vega magnitude (1)
61- 65 F5.3 mag e_Unc [0.001/1.1]? Uncertainty in Unc (1)
--------------------------------------------------------------------------------
Note (1): Null values correspond to cases where no measurement was
made. E.g., if there was no observation within a source density
range for a given filter within a certain flux bin, there is no
measurement of completeness, bias or uncertainty
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Short Field Name (G1)
8- 14 F7.4 deg RAdeg [9.5/86.6] Average Catalog Right Ascension (J2000)
16- 23 F8.4 deg DEdeg [-73.5/-65.5] Average Catalog Declination (J2000)
25- 28 F4.1 mag F225W [25.3/26.4]? Completeness, F225W Vega magnitude (1)
30- 33 F4.1 mag F275W [25.1/26.8]? Completeness, F275W Vega magnitude (1)
35- 38 F4.1 mag F336W [25.1/27.9]? Completeness, F336W Vega magnitude (1)
40- 43 F4.1 mag F475W [26/28.6] Completeness, F475W Vega magnitude (1)
45- 48 F4.1 mag F814W [23.5/26] Completeness, F814W Vega magnitude (1)
50- 53 F4.1 mag F110W [23.1/25]? Completeness, F110W Vega magnitude (1)
55- 58 F4.1 mag F160W [22.6/29.4]? Completeness, F160W Vega magnitude (1)
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Note (1): 50% completeness limits.
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Global notes:
Note (G1): Each field obtains two names: one short and one long. The short
names are formatted as "L(S)MC_n", where n is a number corresponding
to the order in which the field was observed in the survey (e.g.,
SMC_15). All values of n are not present in the table, as some
observations overlapped with other fields, and therefore those
exposures were processed together. In addition, 13 fields suffered
from guide star failures or other imaging artifacts that made them
unusable for photometry. Overall, 109 fields were observed through
2023 February, and the 96 without observing failures are presented
here. The rest of the Scylla survey, comprising observations of
27 fields between 2023 February and August, will be presented in a
future release.
The long field names are formatted as "[PID]_[galaxy]-[distance from
galaxy center in arcsec][cardinal direction]-[telescope rotation angle
in deg (V3PA)]", where PID is the HST program ID under which the
observation was taken (e.g., 15891_SMC-4292sw-13841). The long-form
names are used for a qualitative assessment of the field location
within each galaxy, and therefore the lack of precision in the name
(i.e., using an integer value for the rotation angle) is not a
significant issue.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Aug-2025