Pulsating Stars in the Milky Way: From the IRSF and more · IRSF surveys toward the GC and Bulge Region range #(FOVs) Area Obs. Duration #(Obs) Centre ℓ=0 12 0.17 deg2 2001—2008

Pulsating Stars in the Milky Way:From the IRSF and more

Noriyuki Matsunaga(The University of Tokyo)

Manchester, 25 June 2004

IRSF + SIRIUS1.4-m telescope in Sutherland (SAAO)SIRIUS: FOV: about 7.7’ x 7.7’ Pixel Scale: 0.453”/pix, Simultaneous JHKs images.

It has been steadily working for over 17 years since 2000, during which 170+ papers were published.24+ PhD theses (20 in JP, 3 in SA)

Some IRSF highlights on variables

•Galactic Centre/Bulge• Miras (Matsunaga+09), Cepheids (Matsunaga+11, 13, 16)

•Globular clusters• Type II Cepheids (Matsunaga+06), Miras (Sloan+10)

•LMC/SMC• Ita et al. (2004ab, more time-series catalogs in prep.)

•Local Group galaxies• Leo I (Miras/AGBs, Menzies+06)• Fornax (Miras/AGBｓ, Whitelock+09)• Phoenix (Miras/AGBs, Menzies+08)• Sculptor (Miras/AGBs, Menzies+11)• NGC6822 (Cepheids Feast+12; Miras/AGBs Whitelock+13)

My stays in Sutherland• 80 weeks in 16 years (~1.5 years in total)

• IRSF except the previous stay for 74inch/SpUpNIC

• Michael kindly invited me to dinner almost every visit.

74 inch

PhD Current position

#(w

eeks

)

OutlineIntroduction

• Pulsating stars as tracers of the Milky Way

Case study 1: Cepheids around the GC and beyond (Matsunaga et al. 2016, MNRAS, 462, 414)

• Importance of the interstellar extinction in the MW studies

Case study 2: Carbon-rich Miras in the Galactic bulge (Matsunaga et al. 2017, MNRAS, 469, 4949)

• Importance of spectroscopic follow-ups in the MW studies

Pulsating stars What pulsating stars can tell us.

Pulsating stars as tracers• Period-luminosity relation → Distance

• Unique evolutionary stage →Age

• Kinematic and Chemical information can be added with Mira

Classical Cepheid

Type II Cepheid

Gautchy & Saio (1995)

RR Lyr

Sun

GC

MW Cepheids from classical surveys

• Distant Cepheids in the Galactic disc are obscured. The distribution of ~500 Cepheids from DDO

database:overlaid on the illustration by GLIMPSE project (2008)

Cepheids waiting to be found•

Sun GC

to be detected by Gaianot to be detected by Gaia

Simulation of Cepheids to be detected by Gaia (Windmark et al. 2011)

Cepheids/Miras remain important.

• Many new to be found by OGLE, VVV, Gaia, LSST...

• No Gaia parallaxes for a large part of the disk.

• Cepheids and Miras are bright (especially in the IR) and can be detected across the disk.

Gaia’s first sky map (2016 Sep)

Cepheids around the Galactic Center and beyond

Case Study 1

Matsunaga et al. 2016, MNRAS, 462, 414

Sun

IRSF surveys toward the GC and Bulge

Region range #(FOVs)

Area Obs. Duration

#(Obs)Centre ℓ=0 12 0.17

deg22001—2008 ~90

Bulge -10

Distribution of detected Cepheids29 Classical Cepheids

Distribution of detected Cepheids

4 classical Cepheids in the Nuclear Stellar Disc: previously reported in NM et al. (2011, 13, 15)

29 Classical Cepheids




Matsunaga et al. (2011)

All 4 have P~20 days, aged ~25 Myr.

~0.1 M/yrat ~25 Myr ago

Distribution of detected Cepheids29 Classical Cepheids



25 classical Cepheids beyond the bulge




25 classical Cepheids beyond the bulge

No classical Cepheids within 2.5 kpc of the GC except 4 in the Nuclear Stellar Disc (|l|

Conflicting results•Dekany et al. (2015) reported a significantly different distribution of Cepheids the Galactic disk.

Our work (shallower) Dekany et al. (2015)

37 classical Ceps

from VVV

29 classical Cepsfrom IRSF/SIRIUS

Conflicting results•Dekany et al. (2015) reported a significantly different distribution of Cepheids the Galactic disk.

Our work (shallower) Dekany et al. (2015)

37 classical Ceps

from VVV

29 classical Cepsfrom IRSF/SIRIUS

11 Cepheids are common, and μ0(ours) are systematically larger than μ0 (Dekany et al.).

Impact of the extinction law•

Label Reference Data

C89 Cardelli+1989 Mixed 1.82N06 Nishiyama+2006 IRSF 1.44

N09 Nishiyama+2009 2MASS 1.61

AG15 Alonso-Garcia+2015

VVV 1.28

M16 Majaess+2016 VVV 1.49

13/26






VVV 1.28

M16 Majaess+2016 VVV 1.49

A classical value in Cardelli et al. (1989)

13/26






VVV 1.28

M16 Majaess+2016 VVV 1.49These works consider the direction of the bulge.

A classical value in Cardelli et al. (1989)

13/26

Matsunaga et al. (2016) used the N06 coefficient.


Dekany et al. (2015) used the N09 coefficient.


Dekany et al. (2015) used the N09 coefficient.

~0.3 mag difference

4 Cepheids in the NSD• One of the young stellar populations found in the NSD.

• Radial velocities also support the membership.

l-v diagram for Cepheids compared with CO gas and orbits around the GC


3 Cepheids within 35 pc (projected) of the GC


+1 at ~50 pc

y-axis:Apparent modulus=True modulus + Extinction

x-axis: Color excess

Bulge red clumps split into many sub-regions give AKs/EH-Ks =1.44(Nishiyama+06a)y-axis:

Apparent modulus=True modulus + Extinction


Bulge red clumps split into many sub-regions give AKs/EH-Ks =1.44(Nishiyama+06a)

The distance modulus to the GC(μ0=14.5±0.15 mag; Nishiyama+06b)




4 NSD Cepheids


PLRs in H and Ks can put individual Cepheids on this diagram (without assuming the extinction law or the distance).


4 NSD Cepheids


AKs/EH-Ks



The Nishiyama law is consistent with that the 4 Cepheids are at the GC distance.

AKs/EH-Ks




25 other Cepheids in our survey

AKs/EH-Ks



AKs/EH-Ks



Also, we found no Cepheids on the nearer side.

AKs/EH-Ks


A lack of young stars•The extinction law of A(Ks)/E(H—Ks)=1.44 is used for the both samples (Dekany et al. 2015 and ours).

•Very few, if any, Cepheids are present within

With A(Ks)/E(H-Ks)=1.44 for both samples

4 Cepheids in the NSD/CMZ.

A lack of Cepheids at RGC

Section Summary

•4 Cepheids in the NSD, and new ones across the disk are being found.

•A lack of young stars in the inner ~2.5 kpc except those in the NSD (< 200 pc of Sgr A*).

•The extinction law, A(Ks)/E(H-Ks), has a large impact on drawing the distribution of stars in the Galactic disk (Matsunaga+2016).•Around the Galactic bulge, A(Ks)/E(H-Ks) is ~1.44 (Nishiyama+06), supported by the 4 Matsunaga et al. 2016, MNRAS, 462, 414

Carbon-rich Miras in the Galactic bulge

Matsunaga et al. 2017, MNRAS, 469, 4949—4956

Case Study 2

Oxygen-rich or carbon-rich• Some AGB stars have more C than O at the surface.

• 3rd dredge-up from the stellar interior• Mass transfer from the binary companion

O-rich

C-richMaercker (2009)

Dependency on age and metal•The frequency of C-rich evolved stars can be considered as a population indicator.

• Being applied to nearby galaxies (e.g. Boyer et al. 2013).

C-rich/O-rich ratio at the AGB phase (Marigo et al. 2013)




Old AGB stars don’t evolve into C-rich stars.





Intermediate-age stars become C-rich AGB stars（especially if metal-poor).






Metal-rich stars tend to avoid evolving into C-rich stars.







No C-rich AGB stars had been confirmed in the bulge. ⇔ The dominant population of the bulge is old and metal-rich.







No C-rich AGB stars had been confirmed in the bulge. ⇔ The dominant population of the bulge is old and metal-rich.(5 Gyr, [M/H]=0)

C-rich Miras discovered•Target selection based on (J-Ks) and (9-18) colors

•Low-resolution spectra from SAAO 74inch/SpUpNIC

•6 C-rich Miras among OGLE-III bulge Miras and

2 additional C-rich Miras from Catchpole+2016

Distances to the C-rich Miras•Relatively large errors remain due to the mix of interstellar and circumstellar extinction.

•4 Miras (and maybe another) are within the bulge.

3 foreground (including a symbiotic

C-rich Mira in Miszalski+13)



4 members





1 background?

4 members



The origin of C-rich Miras

The origin of C-rich Miras• Intermediate-age stars (around 0.5—3 Gyr) ??

• If they become C-rich stars after the 3rd dredge-up process.

• They should be not-so-metal-rich and less oxygen enhanced.

•Still old objects ??• If the origin is mass transfers or mergers in binary systems.

• (Possibly related) Blue stragglers exist in the bulge (e.g. Clarkson et al. 2011).

• Even a rare evolutionary path may be important to explain a rare object like the bulge C-rich Miras.

•Accretion from a (merged) dwarf galaxy ??

Section Summary

•4—5 carbon-rich Miras are identified in the bulge for the first time.

•Representing a rare population in the bulge, but their origins are unclear.

• May be intermediate-age stars (0.5—3 Gyr).• May be old stars affected by binary evolution.• May be accreted from a (merged) dwarf galaxy.

Matsunaga et al. 2017, MNRAS, 469, 4949—4956

Concluding remarks

Take-home messages•A large number of new pulsating stars across the Galaxy are expected from large surveys: OGLE, VVV, Gaia, LSST…

•Characterizing the interstellar extinction is an urgent task for mapping the wide area of disk.•Distance indicators with distances determined independent of extinction are valuable.

•Spectroscopic follow-up will be crucial.•Kinematics and chemical abundances

5 Cepheids in the disc flare• Feast et al. 2014, Nature 509, 342• Identified among OGLE-III Cepheids toward the bulge (Soszynski et al. 2011, AcA, 61, 285).

• The first stars ever confirmed to be in the disc flare.• They belong to the disc (rather than Sgr dSph).

• The kinematics are consistent with the disc rotation.

Cepheids identified far from the plane

5 Cepheids in the disc flare• Feast et al. 2014, Nature 509, 342• Identified among OGLE-III Cepheids toward the bulge (Soszynski et al. 2011, AcA, 61, 285).

• The first stars ever confirmed to be in the disc flare.• They belong to the disc (rather than Sgr dSph).

• The kinematics are consistent with the disc rotation.

Cepheids identified far from the plane

Confirmed by SALT spectroscopy!

PRIME

64 Mpixel (4 chips of H4RG) infrared camera to be attached to a new 1.8-m telescope in Sutherland

PIIRSF MOA in New Zealand

SAAO Project Scientist for PRIME:David Buckley

in NAOJ

No K band or longer in order to keep the optics and the telescope feasible.

Nights distribution(under discussion)•A large fraction (~1/2) for the microlensing survey towards the Galactic bulge

•The other (mainly the non-bulge seasons) will be separated by the contributing institutes:

• Osaka University• NAOJ (Astrobiology center) and Univ Tokyo• University of Maryland and NASA• SAAO• Joint projects between these (and other)

H=7—17 mag w. IRSF/SIRIUS

Limits w. PRIME is not so different, but the field-of-view is ~80 times larger.

Survey strategy being discussed:a few sets of different cadence will be combined for studying microlensing events and other objects.

J

MOU between Osaka Univand SAAO is being discussed.

2020 ?

Documents

Pulsating Stars in the Milky Way: From the IRSF and more · IRSF surveys toward the GC and Bulge Region range #(FOVs) Area Obs. Duration #(Obs) Centre ℓ=0 12 0.17 deg2 2001—2008