Pulsating Stars in the Milky Way: From the IRSF and more · IRSF surveys toward the GC and Bulge...
Transcript of Pulsating Stars in the Milky Way: From the IRSF and more · IRSF surveys toward the GC and Bulge...
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Pulsating Stars in the Milky Way:From the IRSF and more
Noriyuki Matsunaga(The University of Tokyo)
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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)
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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)
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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
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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
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Pulsating stars What pulsating stars can tell us.
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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
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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)
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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)
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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)
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Cepheids around the Galactic Center and beyond
Case Study 1
Matsunaga et al. 2016, MNRAS, 462, 414
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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
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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
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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
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Distribution of detected Cepheids29 Classical Cepheids
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Distribution of detected Cepheids
4 classical Cepheids in the Nuclear Stellar Disc: previously reported in NM et al. (2011, 13, 15)
29 Classical Cepheids
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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
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Distribution of detected Cepheids29 Classical Cepheids
4 classical Cepheids in the Nuclear Stellar Disc: previously reported in NM et al. (2011, 13, 15)
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Distribution of detected Cepheids
25 classical Cepheids beyond the bulge
29 Classical Cepheids
4 classical Cepheids in the Nuclear Stellar Disc: previously reported in NM et al. (2011, 13, 15)
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Distribution of detected Cepheids
25 classical Cepheids beyond the bulge
No classical Cepheids within 2.5 kpc of the GC except 4 in the Nuclear Stellar Disc (|l|
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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
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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.).
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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
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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
A classical value in Cardelli et al. (1989)
13/26
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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 1.49These works consider the direction of the bulge.
A classical value in Cardelli et al. (1989)
13/26
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Matsunaga et al. (2016) used the N06 coefficient.
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Matsunaga et al. (2016) used the N06 coefficient.
Dekany et al. (2015) used the N09 coefficient.
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Matsunaga et al. (2016) used the N06 coefficient.
Dekany et al. (2015) used the N09 coefficient.
~0.3 mag difference
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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
Matsunaga et al. (2015)
3 Cepheids within 35 pc (projected) of the GC
Matsunaga et al. (2011)
+1 at ~50 pc
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y-axis:Apparent modulus=True modulus + Extinction
x-axis: Color excess
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Bulge red clumps split into many sub-regions give AKs/EH-Ks =1.44(Nishiyama+06a)y-axis:
Apparent modulus=True modulus + Extinction
x-axis: Color excess
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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)
y-axis:Apparent modulus=True modulus + Extinction
x-axis: Color excess
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y-axis:Apparent modulus=True modulus + Extinction
4 NSD Cepheids
x-axis: Color excess
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PLRs in H and Ks can put individual Cepheids on this diagram (without assuming the extinction law or the distance).
y-axis:Apparent modulus=True modulus + Extinction
4 NSD Cepheids
x-axis: Color excess
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AKs/EH-Ks
y-axis:Apparent modulus=True modulus + Extinction
x-axis: Color excess
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The Nishiyama law is consistent with that the 4 Cepheids are at the GC distance.
AKs/EH-Ks
y-axis:Apparent modulus=True modulus + Extinction
x-axis: Color excess
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y-axis:Apparent modulus=True modulus + Extinction
25 other Cepheids in our survey
AKs/EH-Ks
x-axis: Color excess
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y-axis:Apparent modulus=True modulus + Extinction
AKs/EH-Ks
x-axis: Color excess
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y-axis:Apparent modulus=True modulus + Extinction
Also, we found no Cepheids on the nearer side.
AKs/EH-Ks
x-axis: Color excess
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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
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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
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Carbon-rich Miras in the Galactic bulge
Matsunaga et al. 2017, MNRAS, 469, 4949—4956
Case Study 2
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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)
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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)
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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.
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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).
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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.
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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.
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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.
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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.(5 Gyr, [M/H]=0)
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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
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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)
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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.
4 members
3 foreground (including a symbiotic
C-rich Mira in Miszalski+13)
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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.
1 background?
4 members
3 foreground (including a symbiotic
C-rich Mira in Miszalski+13)
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The origin of C-rich Miras
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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 ??
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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
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Concluding remarks
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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
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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
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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!
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PRIME
64 Mpixel (4 chips of H4RG) infrared camera to be attached to a new 1.8-m telescope in Sutherland
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PIIRSF MOA in New Zealand
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SAAO Project Scientist for PRIME:David Buckley
in NAOJ
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No K band or longer in order to keep the optics and the telescope feasible.
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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)
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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
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MOU between Osaka Univand SAAO is being discussed.
2020 ?
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End