The Milky Way and Resolved galaxies with China Space Station Optical Survey Chao Liu (NAOC) Team members: Jian Gao (BNU), Xiangxiang Xue (NAOC), Jing Zhong (SHAO), Zhou Fan (NAOC), Kefeng Tan (NAOC), Haining Li (NAOC) et al.
Advantages for MW and resolved galaxies • High spatial resolution (0.075”/pixel) good for crowd fields • Potential for proper motions • 3 epochs only with CSS-OS: <1mas@r=24mag (c.f. Z-X. Qi) • Or 2 epochs from CSS-OS+Euclid(+LSST) • Large sky area coverage (MW is located everywhere) • Deep photometry (r~25 mag) • Slitless spectroscopy (better stellar parameters)
Virial radius of MW LMC Virgo NGC891 M101 M81 M31
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Parts of the ladder of the universe a few-10 pc 10-100 kpc 1 Mpc 10 Mpc • Stars • Star clusters • Dwarf galaxies • Milky Way • Local group • Resolved galaxies
Stellar physics • Binaries, pulsators, and peculiar stars • Evolution of the binary systems is big challenge, which is related to many interesting topics, e.g. SNIa progenitors, formation history of galaxies, sources of gravitational wave etc. • Pulsators (Cepheid, RRLy etc.) can be used as standard candles • Peculiar stars, especially rare stars in the evolutionary track due to extremely short time scales are critical to understand the full process of the stellar evolution, especially in the very beginning and near-end phases
Belokurov et al. 2016 Scatters of magnitudes in di ff erent epochs
Normal stars RRLy Ivezic et al. 2000
Goals of stellar physics • Identify variables from magnitude di ff erences between 2 epochs • e.g. RRLy within 1Mpc (inc. M31) • Color index can help to distinguish the types of the variables • Eclipse binaries can be identified • Accurate distribution of the stellar loci distribution in color-color space helps to give fraction of binaries • Identify rare objects from color-color diagrams • e.g. WDs within several 10kpc (inc.LMC/SMC)
Star clusters • see Jing Zhong’s talk
The Milky Way • The halo (Xiangxiang,Xue’s talk) • The disk: 3D extinction and extinction law at various sightlines, global structure (size, structural parameters, flare, warp, oscillations (wobbly disk)), kinematics (with PMs only), chemo-kinematics (photometric metallicity or metallicity from slitless spectra) • The bulge: Global structure, stellar populations traced by di ff erent types of stars, kinematics and dynamics with PMs
Proposed survey strategy
Proposed survey strategy
Proposed survey strategy
Proposed survey strategy
Proposed survey strategy
Stellar parameters • Basic parameters obtained from photometry and slitless spectra • E ff ective temperature, metallicity, surface gravity (Te ff , [Fe/H], logg). Accuracy: ∆ Te ff ~150K, ∆ [fe/H]~0.2-0.3 dex, ∆ logg~0.3-0.5 dex for AFGK stars • Photometric parallax from multi-band colors calibrated with Gaia (Absolute magnitudes: M NUV , M u , M g , M r , M i , M z , M y ). Meanwhile, extinctions from relative reddening • Proper motions from multi-epoch data (CSS-OS only or synergy with Euclid and LSST) ( 𝝂 _ α cos 𝜺 , 𝝂 _ 𝜺 ). Accuracy <1mas@r=24mag
Keller et al. 2007
Keller et al. 2007 v band filter is not only sensitive to metallicity but also to surface gravity!
The Galactic structure learnt from LAMOST survey
The Galactic structure learnt from LAMOST survey Dark halo Stellar halo Tidal streams Thick disk Thin disk Bulge/Bar Satellites
The Galactic structure learnt from LAMOST survey Dark halo Stellar halo Oblate-spherical halo Tidal streams New tidal streams Age variation in warp Thick disk Thin disk Flare with young pop. Larger disk Bulge/Bar Satellites
� ∝r -5.0 The halo 5000+ RGB stars from DR3 with [Fe/H]<-1dex q and MK<-4 q is variable with r r ln ν Liu et al. 2017 ln r Xu, LC et al. 2017
The disk The disc is more extended • At R=19kpc, the fraction of disc • pop. is still ~10% No truncation, break, bend-up • feature is found in the outer disc It simply follow an exp. profile and • smoothly transition to the halo Liu et al. 2017
Xu et al. 2015
The Bulge Lecureur et al 2007 Howes et al. 2015 Ness et al. 2016
The Bulge Cao et al. 2013 Vasquez et al. 2013
Goals of the Milky Way science • Detect the border of the Milky Way • Multiple populations halo/disk • Map the shape of the halo • With PMs • Global structures, • Dynamical mass of the Galaxy substructures and the disk mass of the MW • Derive the 3D structural • chemo-dynamical evolution of parameters of the Galactic disk the Milky Way • Scale heights, scale length • Tidal substructures in the halo • oscillations, flare, warp • kinematics/dynamics of the bulge/bar • The shape of the bulge
Resolved galaxies • Well discriminate individual stars from globular clusters in very nearby galaxies (LMC/SMC/M31 etc) • Wide fields allow an e ffi cient imaging for the whole nearby galaxies, including disks, bulges, and stellar halos (outskirts) • Multi-band photometry good for trace di ff erent populations
Studies on Globular clusters in the Local Group(M31/M33, M81/M82, etc.) • 1. Discover more GCs 2. Multiple population studies of GCs • Multiple population in GCs have been widely studied in Discovering more GCs, especially in the halo of galaxies, the Milky Way, LMC and SMC. Detailed studies on can provide important clues on the accretion histories of M31/M33 GCs could enhance our understanding of the the host galaxies. The recent large project PHAT done by Hubble telescope only covers the inner disk of M31. chemical enrichment and formation histories of these clusters. NG NGC2808 PAndAS (CFHT) Y~0.38 Y~0.24 Y~0.28 Piotto et al. (2007)
Studies on Globular clusters in the Local Group • 3. Stellar population studies of GCs 4. Structural studies of GCs • Spatial structures and dynamics of GCs is of great Stellar population, including age and metallicity, can importance for understanding their formation be effectively used to constrain the formation and condition, dynamical evolution, and discruption within evolution histories of the host galaxies. The most reliable method is fitting the isochrones to the CMDs of the environment of their galaxies. This work has been GCs, but only few GCs in M31/M33 have observations done for few GCs in M31 (< 100) and M33 (< 10) . well enough to do such work. K66, W, S represent different dynamical models; F555W/F814W are filters in HST . Williams & Hodge (2001) Wang et al. (2013)
Stellar Astrophysics in M31 [Fe/H], Age and Mass Tanaka et al. (2010)
Stars in nearby galaxies Karachentsev et al. 2013
A deep census of the satellite galaxies of the MW and M31 Vast polar structure (VPOS)? • Missing satellite problem or not? • Constrain the nature of the dark matter particle •
2 epochs HST obs. between 5-7.5 yr Sohn et al. 2012
The proper motion of M31 • 800kpc, 200km/s==>0.05mas/yr • 10/20/30 years ： 0.5/1.0/1.6mas • It is possible to be detected by combining with HST(~0.02”/pixel), Euclid and PAndAS （ 0.187”/ pixel+0.7”seeing ） • Proper motions of the globular clusters in M31 can also be derived by combining with HST archive data
Goals of resolved galaxies • Systematic survey for globular clusters in nearby galaxies, better address the multi-population issue in GCs • Formation and evolution of the nearby galaxies will be studied in the similar way to the MW, i.e. by using individual stars • Proper motions help to reveal the kinematic/dynamic features of the local group
Interstellar dust/extinction • Di ff used region : extinction law covering from NUV to near infrared in di ff erent systems (MW, LMC/SMC, M31, and nearby resolved galaxies) • Dark clouds : combine with infrared photometric data (WISE etc.) in the bulge direction, LMC/SMC etc. • Goals : extinction laws in di ff erent environments: di ff used/dark regions, MW, LMC/SMC/other galaxies
Drain 2003
Toward the bulge (Baade window) Nataf et al. 2013
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