Parallaxes at 1.6 GHz

Transcription

1 XKCD: Time (frame 2395) Parallaxes at 1.6 GHz OH maser and AGBs (: aka why should we care about the SKA? Gabor Orosz Kagoshima University VERA UM14 Kagoshima, Japan Mitaka, Tokyo, Japan

2 Thank you for the financial support!

3 XKCD: Astronomy Hiroshi Imai Maria Rioja Richard Dodson Sandor Frey Akiharu Nakagawa Ross Burns Dieter Engels Sandra Etoka Steve Goldman Ambra Nanni Paola Marigo Daniel Tafoya Yoshiharu Asaki Hiroyuki Nakanishi

4 A motivational speech Why care about low frequencies? Why care about OH masers? Why care about old stars?

5 A motivational speech Why care about low frequencies? Why care about OH masers? Why care about old stars?

6 A motivational speech Why care about low frequencies? Why care about OH masers? Why care about old stars?

7 A motivational speech Why care about low frequencies? Why care about OH masers? Why care about old stars?

8 22 GHz a dream realized thanks to BeSSeL and VERA Spiral arms of the MWG water and methanol parallaxes fitting log-periodic spiral forms Reid et al 216

9 The challenge of low frequency phase-referencing The dispersive ionosphere! PR 1º PR 4º / TECU 2 Peterson et al 211 ionosphere (5 TECU) ionosphere (.5 TECU) troposphere (3 cm) 1.6 GHz 1.6

10 The challenge of low frequency phase-referencing The dispersive ionosphere! PR 1º PR 4º / TECU 2 Peterson et al 211 ionosphere (5 TECU) ionosphere (.5 TECU) troposphere (3 cm) Low Freq. High Freq. 1.6 GHz 1.6

11 The challenge of low frequency phase-referencing The dispersive ionosphere! PR 1º PR 4º / TECU 2 Peterson et al 211 ionosphere (5 TECU) ionosphere (.5 TECU) troposphere (3 cm) 1.6 GHz 1. reduce ΔTECU 1.6

12 Multi-freq phase-ref (from Richard Dodson) BL Lac Solve for delays (per IF) across all frequencies TEC from τ Small errors in ΔTEC require Inclusion of low frequency (L-band) K band GHz Wide C band GHz L band GHz Errors in ΔTEC ~.1 TECU Low Frequency Astrometry School: Hobart June

13 The challenge of low frequency phase-referencing The dispersive ionosphere! PR 1º PR 4º / TECU 2 Peterson et al 211 ionosphere (5 TECU) ionosphere (.5 TECU) troposphere (3 cm) 1.6 GHz 2. reduce Θsep 1.6

14 Concept of multi-calibrator PR: MultiView adapted from Lonsdale 24 Calibrator Target Calibrator FOV << S B >> S Antenna Beam Field of View (FOV) Wavefront Ionosphere temporal and spatial variability t cycle Ionospheric Irregularity Scale (S) t cycle Baseline (B) IONOSPHERIC WEDGE Spatial structure (frequency/weather/direction) MultiView models the phase-screen around the target: direction dependent calibration

15 Epoch I Epoch II Average of VTEC over mainland USA (TECU) Epoch I Epoch II Time from start of observation (hours) 15 BR-PT (1-9) 15 BR-PT (1-9) NL-PT (7-9) 15 NL-PT (7-9) Phase (deg) Phase (deg) OV-PT (8-9) 15 OV-PT (8-9) Epoch I MultiView PR (w/ C2, ~2º) PR (w/ C1, ~4º) Epoch II Universal time (hours) Universal time (hours)

16 MV Demo: Quasar astrometry Dec. offset (mas) 18 Repeatability between Epochs Systematics Astrometry at C3.I 16 thermal 14 noise C3.II 6 level! 4 2 MV.II MV.I C2.I -2 R.A. offset (mas) C1.II C1.I -4 C2.II -6 Flux recovered Astrometric Error per measurement ~ 1 µas MultiView vs. PR 2º, 4º, 6º: Position Accuracy σpos θsep MV C2 C Separation angle (deg) C Positional error (mas) MV.II ~ 12 μas MV.I

17 The challenge of low frequency phase-referencing The dispersive ionosphere! flagged MK BR-HN flagged KP PT flagged KP flagged SC FD-KP Dec. offset (mas) (a) OH138, epoch I (b) OH138, epoch II (c) OH138, epoch III (d) OH138, epoch IV R.A. offset (mas) R.A. offset (mas) R.A. offset (mas) R.A. offset (mas) all systematically shifted positions include data from SAME ANTENNA 3. flag data showing systematic errors

18 Correlated flux density (Jy beam -1 ) Trig. distances to OH/IR stars using 1612 masers Frequency (MHz) Frequency (MHz) (a) OH (b) OH August 1, 214 February 17, 215 June 8, 215 July 7, 215 Stokes I Stokes V LSR velocity (km s -1 ) Correlated flux density (Jy beam -1 ) February 16, 214 May 7, 214 August 7, 214 February 22, 215 Stokes I Stokes V LSR velocity (km s -1 ) 2.74 ±.39 mas (14%).49 ±.14 mas (29%) Dec. offset (mas) Aug. 1 Offset (mas) R.A. Offset (mas) R.A. Dec. offset (mas) Feb. 16 Offset (mas) R.A. Offset (mas) 1-1 R.A Jul R.A. offset (mas) Dec Epoch (years) -4-6 Dec Epoch (years) Feb R.A. offset (mas) -6 Dec Epoch (years) -2 Dec Epoch (years)

19 So we have our trigonometric distances to old stars The question remains: Why care about old stars? gori gori gori gori

20 Stellar evolution and physics Semiregular (SRa & SRb, giants) OH maser H 2 O maser Semiregular (SRc, supergiants) H 2 O maser Mira (giants) OH maser H 2 O maser SiO maser OH/IR (giants) OH maser (solid) phase-lag (open) Ita et al. 24 (C & C') Whitelock et al. 28 Nakagawa et al. 214 Nakagawa et al st overtone (C') M K -9-8 OH128 OH138-7 fundamental mode (C) Log P

21 Stellar evolution and physics Semiregular (SRa & SRb, giants) OH maser SED from Steve Goldman Semiregular (SRc, supergiants) H 2 O maser Mira (giants) OH maser H 2 O maser SiO maser OH/IR (giants) OH maser (solid) phase-lag (open) Ita et al. 24 (C & C') Whitelock et al. 28 Nakagawa et al. 214 get Nakagawa luminosity et al. 216 H 2 O maser 1 st overtone (C') M K -9-8 OH128 OH138 corrected for extinction -7 fundamental mode (C) Log P

22 Stellar evolution and physics Semiregular (SRa & SRb, giants) OH maser get luminosity, opacity Semiregular (SRc, supergiants) H 2 O maser Mira (giants) OH maser H 2 O maser SiO maser OH/IR (giants) OH maser (solid) phase-lag (open) Ita et al. 24 (C & C') Whitelock et al. 28 Nakagawa et al. 214 Nakagawa et al. 216 SED from Steve Goldman H 2 O maser 1 st overtone (C') M K -9 from Paola Marigo and Ambra Nanni -8 OH128 OH138-7 get Mass fundamental and mass mode (C) loss luminosity below expected Log P corrected for extinction

23 (17 kpc) Semiregular (SRa & SRb, giants) Semiregular (SRc, supergiants) Mira (giants) OH maser (1665 & 1667 MHz) H 2 O maser SiO maser OH/IR (giants) 1612 MHz OH maser (solid) phase-lag (open) Maser molecule used for parallax: Reid et al Zoomed-in view of Solar region (with parallactic distances only) 3 kpc 2 Per 2 kpc 1 1 kpc AqR Loc from Daniel Tafoya -1 CrN SgN LoS Galactic dynamics using AGBs

24 Semiregular (SRa & SRb, giants) Semiregular (SRc, supergiants) Mira (giants) OH/IR (giants) 1612 MHz OH maser (solid) phase-lag (open) Maser molecule used for parallax: OH maser (1665 & 1667 MHz) H 2 O maser SiO maser (17 kpc) Phase-lag distance calibration φ-lag distances don t need VLBI! single dish for OH phase-lag interferometry for size of OH shell ideal SKA surveys!!! Engels et al 215 van Langevelde et al 199 Reid et al Zoomed-in view of Solar region (with parallactic distances only) Per 2 kpc 3 kpc 1 1 kpc -1 CrN AqR SgN Loc LoS from Daniel Tafoya Galactic dynamics using AGBs

25 Science #1 Stellar Evolution Luminosity of our long-period variable AGBs are low and don t seem to depend on puls. period Simulations can t reproduce values for M-type stars and Gal. metallicities Calculated masses are also smaller than thought Effect of metallicity on stellar evolution? Comparison with LMC Science #2 Galactic dynamics AGB stars can be new relaxed tracers of Galactic dynamics Mapping the dynamics of evolved stars is important for understanding how matter circulates in the MWG/Local Group We need good distances to Galactic sources A LOT OH maser parallaxes + phase-lag distance calibration SKA surveys to measure OH shell sizes and phase-lags

26 Pulsar astrometry (L-band VLBI and MultiView) Hulse-Taylor binary pulsar 52. Dec (J2) with Adam Deller 54. Joel Weisberg CX CX s Terzan s 47.2s RA (J2) 47.s 17h 35m 46.8s with Vlad Tudor and James Miller-Jones 1993 Nobel prize in physics proof of gravitational waves

27 Why should we care? 1. Japan and Korea is the center of AGB astrometry: large KVN, KaVA, VERA projects 2. No one is doing low-frequency astrometry for AGBs besides us (yet): VLBA, LBA, EVN 3. A huge interest from AGB astrophysics community for distances: stellar evolution 4. Good follow-up projects when SKA comes