Release Note – Early Data Release: S14A_0b
version 2015.2.4 15:05 JST
Masayuki Tanaka, Masao, Hayashi, Tadafumi Takata, Sogo Mineo, Michitaro Koike, Yuichi Higuchi,
Hisanori Furusawa, Robert Lupton, Paul Price, Jim Bosch, Steve Bickerton, and HSC-SSP Data
Release Team
Critical Issues
1.
In the last release S14A_0, aperture magnitudes (especially with diameter >~ 2arcsec) had
significant offsets from the reference catalog magntiudes, by 0.08 to 0.4 mag dependent on filters.
This magnitude offsets are reduced down to <~0.05 mag in S14A_0b. The DR team thinks that
the aperture magnitudes in this release is more reliable than the last release.
2.
Notice for HSC-1054 to be put: It is found that weighting in the coadd process is not properly
done either in S14A_0 and S14A_0b. This improper handling has led to nonoptimized
signal-to-noise ratios in the resultant coadded images, and discrepancy between PSFs in the
actual coadded images and those (coaddPSFs) used in the pipeline’s measurements. It is
recommended that users should use the PSF and CModel fluxes and shape parameters based on
the PSF determination that are affected. Aperture and Kron measurements should be much
less or not at all affected by this issue.
3.
Calibration of magnitude zeropoint has systematic errors dependent on the sky positions, of
order <~ 0.1 mag, which is due to magnitude errors in the PS1 catalog used for photometric
calibration. The variation in colors of point sources is clearly seen in the r-i vs i-z or g-i vs i-z
colors in the UD-COSMOS field.
1.
Item:

Summary:

Related Issue: DR-XX

Tested Data:

Description:
Astrometric Tests
1.
Comparison of Sky Coordinates of Mosaic Forced-Sources with Reference Catalogs

Summary:
1.
The central patches in a Tract have a scatter of 0.06-0.07 arcsec between (RA, Dec)
determined by astrometry with those in PS1 reference catalogs.
2.
The edge patches may have offsets of 0.05 (UD-COSMOS or SXDS) to 0.1 arcsec
(Wide-XMM).

Related Issue: DR-58

Tested Data:

1.
UD-COSMOS and SXDS (‘5,5’, ‘2,2’, ‘2,8’, ‘8,2’, ‘8,8’)
2.
Wide-XMM (tract: 5322, patch: ‘4,4’,’2,2’,’2,7’,’7,2’,’7,7’)
Description:
We compare the sky coordinates of sources detected on a coadd patch with those in reference
catalogs (PS1_pv1.2c) by using all the sources included in the srcMatch files. No significant
offsets are seen between the measured and reference coordinates in relatively central part of
Tracts in each field, while some visible offsets of 0.05 to 0.1 arcsec are found at the edge patches.
Figure. 1-1. Scatter of residuals of measured RADEC from the reference on all tracts in
UD-COSMOS (Left) and UD-SXDS (Right).
Figure 1-2. Same as Figure 1-1, but for Wide-XMM, Tract=8522, Patch=4,4 (Left), and 2,2
(Right).
2.
Compare the Positions of Objects in HSC Wide Survey and CFHTLS.

Summary:
1. The positions of objects are systematically shifted about 0.25 arcsec along RA direction
and 0.1 arcsec along Dec direction. The shifts along RA direction depend on the positions of
patches in a tract. On the other hand, the value of offset along Dec direction is almost
constant.
2. The values of astrometric offsets increase as objects become dark.

Related Issue: DR-63

Tested Data:
1. HSC Wide (tract: 8522, patch ‘0,0’, ‘4,4’, ‘8,8’)
2. CFHTLS catalog (i-band selected objects: W.I.cat)

Description:
We retrieve i-band selected object in the CFHT catalog and search the most nearest object within 3
arcsec in the HSC catalog. Objects, which match objects in CFHTLS catalog more than two times and
over, are excluded in the analysis.
Figure 2.1-3 show the difference of astrometric positions between the two catalogs along RA and
Dec directions for each patch. The positions of the objects are systematically shifted about 0.1 arcsec
along Dec direction and about 0.25 arcsec along RA direction. The difference of the position along Dec
is constant between patches. On the other hand, the position errors along RA direction are different
for each patch.
Figure 2.4-6 show the position error of the objects for each patch as a function of magnitude in the
HSC catalog. We find that the astrometric errors increase as the magnitude decreases.
Figure 2.1. The astrometric difference between two catalogs. X-axis shows the difference of the
positions of objects for RA between HSC wide survey and CFHTLS. Y-axis shows for Dec. The
analysis is carried out to Patch=0,0.
Figure2.2. Similar to Figure 1. But for patch 4,4.
Figure 2.3. Similar to Figure 1. But for patch 8,8.
Figure 2.4. Position error as a function of object magnitude. X-axis shows the i-band magnitude in
the HSC survey. Y-axis shows the difference of the position. Points (black) show the result for each
object. Points with error bars (red) show the average values in each bin. The error bars show σ/√N,
where N is the number of objects in each bin. The analysis is carried out to Patch=0,0.
Figure 2.5. Similar to Figure 4. But for patch=4,4.
Figure 2.6. Similar to Figure 4. But for patch=8,8.
Photometric Tests
3.
Comparison between forced Kron and CModel Magnitudes (DR-11)

Summary:
There is a filter-dependent offset between forced Kron and CModel, but it can plausibly be
explained by the seeing variation.

Related Issue: DR-12

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d and v3.4.1

Description:
Applied the following flag cuts to select objects with clean photometry:
centroid_sdss_flags = 0
flags_pixel_edge = 0
flags_pixel_interpolated_any = 0
flags_pixel_saturated_any = 0
flags_pixel_cr_any = 0
flags_pixel_bad = 0
flux_kron_flags = 0
cmodel_flux_flags = 0
deblend_nchild = 0 & parent = 0 for non-forced
object_deblend_nchild = 0 & object_parent = 0 for forced
A few comparison figures are shown below (they are for the i-band). Please refer to JIRA for the
other filters. There are filter-dependent offsets, which can be mostly explained by the seeing
varisions. Note that Kron uses the aperture of the same size regardless of the seeing. Rough
seeing sizes in the COSMOS coadds are
g: 0.75 arcsec
r: 0.60 arcsec
i: 0.80 arcsec
z: 0.90 arcsec
y: 0.95 arcsec
There is an offset of 0.03mag between Kron and CModel in the i-band in v2.12.4d, while the
offset is basically zero in v3.4.1. The same trend can be seen in DR-12 (Kron vs CModel in
unforced mode).
4.
Comparison between Unforced Kron and CModel Magnitudes (DR-12)

Summary:
In v2.12.4d, CModel is brighter than Kron by 0.03 mag in all the filters. No tests are
performed for v3.4.1.

Related Issue: DR-11, DR-13

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d

Description:
The same data as in DR-11 are used and the same cuts are applied to ensure clean photometry.
Note that, due to a sky subtraction bug in unforced photometry in v3.4.1, we perform this test
only for v2.12.4d. A comparison between unforced Kron and CModel photometry is shown
below. This is for the i-band, and the other filters can be found on JIRA. We find that CModel
is brighter than Kron by 0.03mag in all the filters. The same trend was observed in the
previous data release (which is not surprising because we use the same version of the code).
5.
Comparison of various photometry between forced and unforced modes (DR-13)

Summary:
The forced and unforced photometry in v2.12.4d is mostly consistent, except for CModel
mags in the r-band, which shows a ~0.035mag offset. The same offset was also observed in
the previous data release, but we do not know what the offset is due to.

Related Issue: DR-12

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d

Description:
Same flag cuts as in DR-11 are applied in order to select objects with clean photometry.
Due to a sky subtraction bug in unforced photometry in v3.4.1, we perform this test only for
v2.12.4d. A few sample figures for the i-band are shown below. Refer to JIRA for more
plots. Our findings are:
Aperture: no offset between forced and unforced photometry
Kron: there are filter-dependent offsets, but they can be explained plausibly by the seeing
variations.
CModel: Mostly consistent except for the r-band, which shows an offset of 0.035mag. The
same offset was seen in the previous data release. We do not know what this offset is due to.
6.
Comparison between HSC Kron and SExtractor’s Kron (DR-14)

Summary:
The agreement is reasonable, although there is a small tilt there.

Related Issue: DR-15

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d

Description:
The same flag cuts as in DR-11 are applied in order to select objects with clean photometry.
Source Extractor v2.19.5 is ran on calexp*fits. Only the i-band images are tested here. Some
of the relevant parameters are:
DETECT_MINAREA 10 # min. # of pixels above threshold
DETECT_THRESH 1.0 # <sigmas> or <threshold>,<ZP> in mag.arcsec-2
ANALYSIS_THRESH 1.0 # <sigmas> or <threshold>,<ZP> in mag.arcsec-2
We confirmed that the result here is not strongly dependent on these parameters. Note that
we do not let SExtractor subtract the sky. The agreement between SExtractor’s Kron and
HSC Kron is good, although there is a small tilt there. The attached figure is for v2.12.4d.
Tests on v3.4.1 are yet to be done (see JIRA for updates).
7.
Comparison between HSC Aperture Mags and SExtractor’s Aperture Mags (DR-15)

Summary:
There is 0.03mag offset in the smallest aperture, but no clear offsets are observed in larger
apertures.

Related Issue: DR-14

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d

Description:
Same test as DR-14 but for aperture mags. There is an offset of 0.03mag in the smallest
aperture. In larger apertures, the offset is gone. This is at least qualitatively consistent
with Bickerton & Lupton 2013, which shows the HSC is more precise than SExtractor in
very small apertures.
8.
Comparison between HSC and Ilbert et al’s COSMOS Catalog (DR-16)

Summary:
V2.12.4d is consistent with the external catalog (except for offsets, which we should not be
worried about). V3.4.1 shows a tilt at faint magnitudes.

Related Issue:

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d and v3.4.1

Description:
First of all, it should be emphasized that the COSMOS catalog from Ilbert et al. 2009 is not
calibrated well and we should not look at any systematic offsets between Ilbert and HSC.
Plotted are Kron from HSC (forced photometry) and Kron from Ilbert et al. These are just
sample plots and please refer to JIRA for more.
v2.12.4d: no clear trend other than the offsets (which we should not be worried about).
v3.4.1: there seems to be a tilt at faint mags. This is also seen in DR-51 which compares
v2.12.4d photometry with v3.4.1 photometry.
9.
Compare Magnitude of Objects in HSC Wide Survey with Magnitude in the CFHTLS Catalog.

Summary:
1. The difference of magnitude between HSC wide survey and CFHTLS is less than 0.1 for
bright objects..
2. While the magnitude difference depends on color of object, the difference of magnitude is
less than 0.2 for objects with r-i>0.

Related Issue: DR-62

Tested Data:
3.
HSC Wide (tract: 8522, patch ‘0,0’, ‘4,4’, ‘8,8’)
4.
CFHTLS catalog (i-band selected objects: W.I.cat)
Description:
We retrieve i-band selected object in the CFHT catalog and search the most nearest object
within 3 arcsec in the HSC catalog. Objects, which match object in CFHTLS catalog more than
two times and over, are excluded in the analysis. We use 3” radius aperture magnitude for the
analysis. We do not consider the effect of Color term.
Figure 3.1 shows the difference of aperture magnitude between HSC and CFHT as a
function of magnitude in HSC wide survey. The average value of the difference is less than
0.1 for bright objects.
Figure 3.2 shows the difference of magnitude as a function of color. The average value of
difference of magnitude is less than 0.2 for r-i>0.
Figure 3.1. Magnitude - difference of magnitude between HSC wide survey and CFHTLS. X-axis is
magnitude in HSC Wide survey. Y-axis is difference of i-band magnitude between CFHT and HSC.
Points (black) show the difference of magnitude for each object. Points with error bars (red) show the
average values in each bin. Error bars show the σ/√N, where N is the number of object in each bin.
Figure 3.2. color - difference of magnitude between HSC wide survey and CFHTLS. X-axis is color
estimated with the magnitude in the CFHTLS catalog. Y-axis is the difference of magnitude. Points
(black) show the difference of i-band magnitude for each object. Points with error bars (red) show the
average values in each bin. Error bars show the σ/√N, where N is the number of object in each bin.
10. Comparison of Color-Color Plots between Sources and SG/SED-Model Stars

Summary:
Colors of point sources are consistent with those estimated from stellar SED templates.
There seems to be no variation in all of the stellar colors between each patch but i-z color in
patch 8,8 in Wide-XMM. In the only patch, the difference of ~0.1 mag is seen (see Figure
DR42-1).

Related Issue: DR-42

Tested Data:
1.
UD-SXDS (v2.12.4d_hsc)
patch: ‘3,3’,’3.5’,’3,7’,’5,3’,’5,5’,’5,7’,’7,3’,’7,5’,’7,7’
catalog: forced-src for each i,z,y-select catalog
2.
Wide-XMM (v3.4.1)
tract: 8522
patch: ‘0,0’,’0,8’,’2,4’,’4,2’,’4,4’ ,’4,6’,’6,4’,’8,0’,’8,8’
catalog: forced-src

Description:
1.
flag cut
centroid_sdss_flags=0,
flags_pixel_edge=0,
flags_pixel_saturated_any=0,
flags_pixel_cr_any=0,
flags_pixel_interpolated_any=0,
flags_pixel_bad=0,
parent=0,
object_deblend_nchild/deblend_nchild=0, detect_is-patch-inner=1 (Wide-XMM)
2.
object selection
classification_extendedness=0, mag_psf,g,r,i,z,y<23.5
3.
analysis
Colors of the point sources are compared with those calculated from the stellar SED
given by Gunn-Stryker (1983). Transmission curves of the HSC filters are taken from
Subaru webpage, and quantum efficiency of FDCCD is taken into account in the
calculation of stellar colors from the SED templates. We use “mag_psf”.
Figure DR42-1. Color-color, g-i versus i-z, diagram in each patch. The colors of point sources in each
patch are compared with those in the central patch (5,5 for UDeep and 4,4 for Wide) and those from
the Gunn-Stryker SED.
Figure DR42-2. Same as Figure DR42-1, but for color-color of r-i versus i-y.
11. Comparison between Measured and Reference Catalog (PS1) Magnitudes

Summary:
1.
Aperture magnitudes have significant offsets from reference magnitudes in each band

Related Issue: DR-67 (former DR-51)

Tested Data:
1.
UD-COSMOS over the Tract in DB mosaic_matchlist (S14A_0 and S14A_0b)
2.
Description:
Measured (non-forced) magnitude and reference magnitudes of the same sources on coadd are
compared over the UD-COSMOS Tract, and compared between the two processing versions (S14A_0
and S14A_0b).
Figure DR51-1a, DR51-1b: mag vs (mag-ref ). in HSC-I, UD-COSMOS, Aperture05 (D=4”). (Left)
S14A_0, (Right) S14A_0b.
Figure. Same as Figure DR51-1{a,b}, but for CModel magnitudes in HSC-I. Again (Left) S14A_0 and
(Right) S14A_0b. Here, only compact sources whose adaptive moments is small enough < 1 (in
HSC-i).
In the HSC-i band, the previous release S14A_0’s aperture05 (4-arcsec) magnitudes had offsets from
the reference mag of ~-0.085, with a mild slope in the magnitude difference where source is getting
brighter than reference at the FOV edges by ~2%. The offsets varied depending on bands (0.1 to 0. 4
mag).
In S14A_0b, we see that the magnitude offset and the slope are much reduced.
The difference (improvement) is due to the too small Sinc radii (for flux scale determination in
PhotoCal and MosaicTask): 7 pix in S14A_0 and 12 pix in S14A_0b.
This effect still exists but smaller with smaller apertures (0.05 to 0.18 mag). The user should be
aware of this systematics.
The offsets in other non-fixed-aperture measurements (PSF, CModel, Kron) were relatively small
since the aperture correction in the pipeline cancel out the influence by the too-small Sinc radii in
S14A_0.
The magnitude offsets (mag_src- mag_ref), tested in the same manners as in the above figures, are
listed. Note that S14A_0 have an additional few percent slope.
aperture05 (D=4"):
S14A_0: g=-0.4, r=-0.1, i=-0.08, z=-0.17, y=-0.4
S14A_0b: g=-0.03, r=-0.02, i=0, z=-0.04, y=-0.05
aperture03 (D=2")
S14A_0: g=-0.18, r=-0.05, i=-0.05, z=-0.07, y=-0.18
S14A_0b: g=+0.03, r=+0.03, i=+0.03, z=+0.05, y=+0.05
Kron:
S14A_0: g=-0.02, r=+0.02, i=+0.03, z=+0.02, y=-0.08
S14A_0b: g=+0.03, r=+0.05, i=+0.04, z=+0.04, y=+0.04
CModel:
S14A_0: g=-0.04, r=0, i=+0.04, z=0, y=-0.1
S14A_0b: g=-0.01, r=+0.03, i=+0.03, z=0, y=0
The
same
test
is
performed
with
the
‘Forced-mode’
magnitudes,
on
the
i-selected
deepCoadd_forced_src fluxes of the sources which are listed in srcMatch, by joining in catalog
database over the UD-COSMOS tract.
The trends in most of combinations of the processing version & measurement kind are close to those
with the non-forced measurements, except the Kron fluxes. The forced-mode Kron fluxes seem to
have large offsets from the reference magnitudes in S14A_0 (HSC-g and HSC-Y), and S14A_0b
(HSC-Y).
The magnitude offsets in the forced-mode measurements (mag_forced_src- mag_ref) for the i-select
sources:
aperture05 (D4"):
S14A_0: g=-0.42, r=-0.1, i=-0.1, z=-0.16, y=-0.4
S14A_0b: g=-0.03, r=-0.02, i=-0.03, z=-0.04, y=-0.05
aperture03 (D=2"):
S14A_0: g=-0.18, r=-0.03, i=-0.05, z=-0.07, y=-0.18
S14A_0b: g=+0.03, r=+0.03, i=+0.03, z=+0.05, y=+0.06
Kron:
S14A_0: g=+0.25, r=-0.01, i=+0.03, z=+0.06, y=+0.15
S14A_0b: g=+0.03, r=+0.02, i=+0.03, z=+0.07, y=+0.12
CModel:
S14A_0: g=+0.01, r=+0.02, i=-0.01 z=+0.02, y=+0.07
S14A_0b: g=-0.01, r=+0.03, i=0.0, z=+0.02, y=+0.02
Tests on Detection and Completeness
12. Item: Number Counts of Sources and Comparison with Published Results

Summary:
Number counts of point sources imply that the measurement of extendedness works for
objects down to m~23.5-24.0. In magnitudes fainter than that, the number counts rapidly
increase and the situation looks unrealistic.
The number counts of extended sources seem to be consistent with the published results
from other surveys. Comparison with the other surveys suggests that the 50% completeness
limits for extended sources are m_i~26.0, m_z~25.0 in UDeep-COSMOS, m_i~26.0,
m_z~25.0 in UDeep-SXDS, and m_r~25.5, m_i~25.5, m_z~25.0 in Wide-XMM.

Related Issue: DR-43

Tested Data:
1.
UDeep-COSMOS (v2.12.4d_hsc)
patch: 25 patches of ‘3,3’..’7,7’
catalog: src for each i,z,y-select catalog
2.
UDeep-SXDS (v2.12.4d_hsc)
patch: 25 patches of ‘3,3’..’7,7’
catalog: src for each i,z,y-select catalog
3.
Wide-XMM (v3.4.1)
tract: 8522
patch: 81 patches of ‘0,0’..’8,8’
catalog: forced-src

Description:
1.
flag cut
flags_pixel_edge=0,
flags_pixel_saturated_any=0,
flags_pixel_cr_any=0,
flags_pixel_bad=0, deblend_nchild=0, detect_is-patch-inner=1
2.
object selection
Objects with classification_extendedness=0 are regarded as point sources, while objects
with classification_extendedness=1 are regarded as extended sources.
3.
Analysis
Number counts in each patch and its average are derived from the catalogs. We use
“mag_psf” for point sources and “mag_aperture” measured with 3”-diameter aperture
for extended sources. We then compare the number counts of extended sources with
published results from other surveys, if possible. Note that the number counts are NOT
corrected for completeness. A ~50% completeness limit is roughly estimated by
comparing with the published results which is corrected for completeness.
■ UDeep-COSMOS
Figure DR43-1. Number
counts for point sources
in U-Deep COSMOS field. Red circles show the average number counts per patch, and the errors are
the standard deviation of the number counts in each patch.
Figure DR43-2. Same as
for extended sources in U-Deep COSMOS field.
■ UDeep-SXDS
for Figure DR43-1, but
Figure DR43-3. Same
as for Figure DR43-1,
but for point sources
in U-Deep SXDS field.
Figure
DR43-4.
DR43-1, but for extended sources in U-Deep SXDS field.
Same as for Figure
■ Wide-XMM
Figure DR43-5. Same as for Figure DR43-1, but for point sources in Wide XMM, tract 8522 field.
Figure DR43-6. Same as for Figure DR43-1, but for extended sources in Wide XMM, tract 8522 field.
Tests on Source Classification
13. Star-galaxy Separation (DR-46)

Summary:
Star-galaxy separation based on classification_extendedness is fairly good at i<~23. But,
both completeness and contamination get worse at fainter mags.

Related Issue:

Tested Data: UD-COSMOS (‘4,4’, ‘4,6’, ‘6,4’, ‘6,6’) reduced with v2.12.4d and v3.4.1

Description:
As in DR-11, flag cuts are applied to ensure good photometry and shape measurements.
Then, this HSC catalog is cross-matched with COSMOS ACS catalog by position. Assuming
that the star/galaxy classifier in the ACS catalog is the truth table, the completeness and
contamination rates (defined below) are computed as a function of i-band mags.
completeness: fraction of ACS point sources that are properly classified as stars by HSC
(classification_extendedness = 0)
contamination: fraction of HSC point sources that are actually extended in ACS
Because only 4 patches are used, the statistics are poor, but the following plots will give us a
sense of how well classification_extendedness works. To the first order, the two versions
deliver similar accuracy (maybe v.3.4.1 is slightly better at faint mags). We should keep in
mind that the classification accuracy is dependent on the seeing and so it varies from field to
field.
EOF