The stellar halo of isolated
central galaxies in the Hyper
Suprime-Cam
imaging Survey
Wenting Wang
Kavli-IPMU
Galaxy evolution workshop 2019
ArXiv 1811.04714
published on line by MNRASCollaborators and coauthors:
Jiaxin Han, Alessandro Sonnenfeld, Naoki Yasuda, Xiangchong Li, Yipeng Jing,Surhud More,Paul A. Price, Robert Lupton, Eli Rykoff, David V. Stark, Ting-Wen Lan,
Masahiro Takada, Song Huang, Wentao Luo, Neta A. Bahcall, Yutaka Komiyama

(ArXiv 1811.04714)

Hyper Suprime-Cam●●●HSC is a gigantic digitalstill camera for 8.2 m
Subaru telescope built by
NAOJ in collaboration withinternational academic
and industrial partners.
104 science CCDs, 1.5
deg FOV in diameter, pixel
size of ~0.168 arcsec.
The HSC pipeline is anenhanced version of theLSST.

(ArXiv 1811.04714)

Hyper Suprime-Cam●●●

HSC is a gigantic digitalstill camera for 8.2 m
Subaru telescope built by
NAOJ in collaboration withinternational academic
and industrial partners.
104 science CCDs, 1.5
deg FOV in diameter, pixel
size of ~0.168 arcsec.
The HSC pipeline is anenhanced version of theLSST.

Use coadd image products- sky background and instrumental features removed by the pipeline(ArXiv 1811.04714)

Isolated central galaxies
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Parent sample: SDSS DR7
spectroscopic Main galaxies
Brightest within the halo virial radius inprojection.

Central fraction

Brightest within three times the virial
velocity along the line-of-sight.
Not within the virial radius of anotherlarger object.
Virial radius and velocity obtained
through abundance matching.
Using photoz probability distribution
to compensate fiber collisions.
Redshift range: 0.05-0.16

completenessBased on a mock galaxy
catalog of semi-analyticalgalaxy formation model(Guo et al., 2011)

(ArXiv 1811.04714)

Isolated central galaxies
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Parent sample: SDSS DR7
spectroscopic Main galaxies
Brightest within the halo virial radius inprojection.

Central fraction

Brightest within three times the virial
velocity along the line-of-sight.
Not within the virial radius of anotherlarger object.
Virial radius and velocity obtained
through abundance matching.
Using photoz probability distribution
to compensate fiber collisions.
Redshift range: 0.05-0.16Galaxy images are stacked!

completenessBased on a mock galaxy
catalog of semi-analyticalgalaxy formation model(Guo et al., 2011)

(ArXiv 1811.04714)

Methodology●Image cutouts●

Cosmic dimming correction●

Source masking by creating g,r and i band stacked
images at first and run Sextractor with different detection
thresholds●

Image resampling to the same WCS: pixel size~0.8 kpc●

Clipping and stacking●

Random sample correction for residual background(ArXiv 1811.04714)

Random stacks●

Random stacks cannot account for incompletemasking of satellite galaxies!

(ArXiv 1811.04714)

Surface Brightness

HSC g,r,i-bands mapped to RGB(Lupton et al. 2004)

HSC r-band

10^9.2-9.9 solar mass
120 kpc
Random stacks are ideally flat.

(ArXiv 1811.04714)

PSF effect
Extended PSF wings

We can go down to 30 mag/arcsec^2, out of which the PSF-free stellar halocontributes 31 mag/arcsec^2 (3-sigma significance).

(ArXiv 1811.04714)

Low and high concentration●Low and high concentration galaxies show
distinct features in their outer stellar halos.

(ArXiv 1811.04714)

Universality of the stellar halo

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Universality of the stellar halo

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Color profiles
Low and high concentration galaxies with 0.05<z<1g-r

g-r

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Color profiles
Low and high concentration galaxies with 0.05<z<1g-r

g-r

Dashed – PSF-free color profiles
The extended PSF wings slightly flattens the color profiles.

(ArXiv 1811.04714)

Systematics in color profiles
Galaxies with 0.05<z<1 - to minimize K-corrections

20 kpc10 kpcg-r
30 kpc(ArXiv 1811.04714)

Systematics in color profiles
Galaxies with 0.05<z<1 - to minimize K-corrections

20 kpc10 kpcg-r
30 kpc●Positive color gradients are sensitive to how
satellite galaxies are masked!

Lowereddetection
thresholds

(ArXiv 1811.04714)

Summary
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The surface brightness profiles centered on isolated central galaxies can berobustly measured up to 120~kpc, and down to 30mag/arcsec^2 (31mag/arcsec^2
for the PSF-free stellar halo with 3-sigma significance).
Our measurements cover a wide stellar mass range for galaxies(9.2<logM*/Msun<11.4).
Stellar halos. are close to universal after scaling the projected radius by the halovirial radius.
The extended PSF wings significantly contaminate the outer stellar halo forsmaller and late-type galaxies!
The red halo effect is less severe for HSC, which uses thicker CCDs. PSF onlytends to slightly flatten the color profiles.
The latest data release of HSC is at least 20 times smaller than SDSS, but wecan push to similar scales + magnitudes and smaller galaxies than previousstudies!
This study can be further extended with data from the future LSST survey.

Thank you!