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Yang Cui Friday July 26 th 2013 Committee: Gerald, Chris, Fabian, Art, Dan

Novel, Efficient Way to Study Origins of Globular Cluster Bimodality Calibration on MC Cluster NGC 1850a Application to GCs in the Sombrero Galaxy. Yang Cui Friday July 26 th 2013 Committee: Gerald, Chris, Fabian, Art, Dan. Presentation outline.

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Yang Cui Friday July 26 th 2013 Committee: Gerald, Chris, Fabian, Art, Dan

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  1. Novel, Efficient Way to Study Origins of Globular Cluster BimodalityCalibration on MC Cluster NGC 1850aApplication to GCs in the Sombrero Galaxy Yang Cui Friday July 26th 2013 Committee: Gerald, Chris, Fabian, Art, Dan

  2. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  3. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  4. Whitmore 99: Antennae Galaxies Nearest full-scale, ongoing merger. FIG. 3.-True-color image of NGC 4038/4039 using UBV I WFPC2 images (U]B for blue, V for green, and I for red; square root scaled image)

  5. FIG. 5. (b) (rotated) Identification image Open circles young clusters (<30 Myr) Open squares intermediate-age clusters (~500 Myr) Filled circles old globular clusters + signs foreground stars

  6. GC formation 3/4 of stellar mass in local universe in spheroids. [Brodie & Strader (2006)] No massive E galaxy has been convincingly shown to lack GC subpopulations. Major star-forming episodes occur during spheroid formation, are typically accompanied by significant GC formation. • Massive star clusters form in all major star-forming events, e.g. in galaxy-galaxy interactions (eg. Schweizer 01; Whitmore+99) • # of new clusters formed scales with amount of gas in interaction (e.g., Kissler-Patig, Forbes & Minniti 98) • Cluster formation efficiency scales with star-formation rate, at least in spirals where it can be measured presently (Larsen & Richtler 00) GC’s integrated properties approximate Simple Stellar Population (SSP). Simplifies determination of their age and metallicity wrt that of the diffuse light of their host galaxies. (not completely true as shown by recent CMD studies of MW GCs) Perhaps most importantly, the properties of GCs (especially metallicities) are correlated with properties of their host galaxy.

  7. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  8. [Brodie & Strader 06] Color distribution of GC system in a galaxy is typically bimodal. Why?

  9. Brodie+12 (NGC3115) confirms color-metallicity relation, claim that most GCs are old (10 Gyr; e.g. Strader+05; Puzia+05) CaT index is insensitive to HB morphology and alpha-element enhancement over metallicities [Z/H]=−2.0 to [Z/H]=0.0 using new stellar population models. Metal richer --------Redder ----------> (color is in magnitudes)

  10. Color Bimodality can be explained by: [Brodie & Strader 06 sec 2.1] • Major merger – mpGC progenitor spirals/ mrGC merger metal-poor GCs are donated by the progenitor spirals and the metal-rich GCs are formed in the gas-rich merger. Ashman & Zepf (1992) and Zepf & Ashman (1993) • Multiphase – mpGCinitl Galaxy formation / mrGC 2nd phase metal-poor GCs were formed in gaseous fragments during the earliest phases of galaxy formation. GC formation was then truncated at high redshift and resumed after a dormant period of a few Gyr. During this second phase the metal-rich GCs and the bulk of the galaxy field stars were formed. • Accretion – mrGC seed galaxy / mpGC accretion metal-rich GCs were formed in situ in a massive seed galaxy, whereas the metal-poor GCs were acquired in the dissipationless accretion of neighboring lower-mass galaxies • Recent: color-metallicity relation non-linear because of hot HB stars? Blakeslee 10; Yoon+11; Cantiello & Blakeslee 12

  11. Color, while efficient to study integrated light, can be strongly dust extinguished. Also, increased age/metallicity both redden color. [Georgiev+11 ] age-metallicity degeneracy [Worthey 94, Worthey 99] http://astro.dur.ac.uk/~rjsmith/stelpops_2010_lec2.pdf

  12. http://ned.ipac.caltech.edu/level5/March11/Chavez/Chavez3.html#Figure%202http://ned.ipac.caltech.edu/level5/March11/Chavez/Chavez3.html#Figure%202 • Similar SED based on MILES • Teal: age = 3Gyr [Fe/H]=+0.3 • White: age = 9Gyr [Fe/H]=+0.0 Worthey 99 Wavelength (Angstroms)

  13. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  14. Observed spectral Indices Element abundances from composite absorption line strengths in integrated-light optical spectraMost common system: Lick/IDS indices25 absorption-line strengths of diagnostic elements (Worthey 94)+Theoretical spectral library e.g. the MILES librarymay break age-metallicity degeneracy

  15. Lick Indices Each is defined by center pass band (shown) & 2 side continuum bands 404 – 647 nm good for Goodman Most popular indices: Hbeta, Mgb, Fe5270, Fe5335 Worthey 99

  16. MILES-based integrated spectra ~1000 star MILES spectral library, 352-750 nm cover range of photosphere parameters + Initial Mass function (IMF) Theoretical isochrones Stellar evolution models  set of integrated light SEDs f(age, metallicity)

  17. Maraston+11 Fig. 21 Compares different model Lick indices calculated: on MILES-based integrated SEDs (white); through MILES-based FF (from Johansson+10, red); models with variable abundance ratios from TMJ for solar-scaled [/Fe] = 0.0 (green) and [/Fe] = 0.3 (yellow).Solid/dashed lines refer to solar/sub-solar −1.3 metallicities. Vazdekis+10 models calculated on SEDs and for same metallicities are teal lines.

  18. Worthey 99

  19. Compare MILES model SED with observed line strength Over range of library, we plot model grids of age-sensitive indicator (e.g. Hbeta) vs metallicity-sensitive indicator (e.g. Mgb, <Fe>)  estimate age & metallicity separately Maraston+11

  20. Norris+08: Gemini-S GMOS spectra of 29 GCs around E gal NGC 3923

  21. Woodley+09 GMOS 340−570 nm for 72 GCs in one galaxy, S/N >30/Ang. Degenerate at upper left & lower right corners – Hbeta is better y axis Model zero point problem – ages > CMD derived ages [Vazdekis+10 6.1.1] Woodley+09 Fig. 7.— Diagnostic plots for all measurements (no duplicate measurements) of GCs in NGC 5128 with S/N> 30/Angstrom (blue circles) and the Milky Way data (Schiavon et al. 2005; Puzia et al. 2002) (yellow squares). The SSP models are from Thomas et al. (2003, 2004) and the Balmer line diagnostic plots are for the grids of [/Fe]= 0.0 dex. The bootstrapping uncertainty is attached to each point and the systematic uncertainty is indicated by the yellow cross in the corner.

  22. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  23. A new efficient way to map Lick indices … http://www.sao.ru/hq/lsfvo/devices/scorpio/ifp/cubes.html … via a series of narrow-band images of complex object to build up spectra across whole field of view. GC is easy, no rotation. Galaxy requires over-scan. I’ll start w/ resolved LMC GCs, then maybe GC systems beyond

  24. Transmission profile of Fabry-Perot is Airy function if etalon plates are perfectly flat, calibrate otherwise. FWHM at each wavelength for SALT/RSS in Rutgers report Etalon1053 Measurements. Transmission Free Spectral Range (FSR) Angstrom http://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_interferometer

  25. I wrote Mathematica code to synthesize optimally each Lick passband I mimic Lick indices by summing many Airy functions. Subtract lower resolution etalon profile to cancel broad wings

  26. An example of how I calculate FP sensitivity I used Monte Carlo to estimate the index uncertainty from sky noise Index S/N vs. exposure time (s) for each etalon channel:

  27. Advantages: If systematics can be controlled, advantages over MOS and IFU: FP gives full spatial resolution/bigger FOV compared to MOS/IFU Spectra of thousands of objects are obtained in exposure series Time/object is comparable to MOS/IFU: e.g. for Sombrero Norris+08: 8 hr w/ Gemini/GMOS  29 GCs SALT RSS/FP: 30 hr  "Hbeta”, "Mgb", "Fe5270", & "Fe5335" for 108 GCs assuming V = 20 SOAR/BTFI (+SAM) comparable (much faster) from smaller sky

  28. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  29. My SALT program is applying my technique to the young Magellanic GC NGC 1850a Why NGC 1850a? One of most luminous and spatially extended (D~2.5') LMC GCs

  30. NGC1850a (70 Myr) + NGC1850b (5 Myr) ½’ West [Gilmozzi+94], ages from MSTO CMD fits Metallicity [Fe/H]derived from Jasniewicz & Thévenin 94 -0.12 +/- 0.03 2 stars Harris & Zaritsky 09 -0.12 +/- 0.03 CMD fitting [Gilmozzi+94] Caloi & Cassatella Z=0.004, 0.009, 0.014 (Zsun = 0.02) Sec. 3.1 quoted from others Santos & Piatti 04 EW of KCa II, G band (CH), MgI, Hδ, Hγ, Hβ 158 of 4540 stars bright enough to photometer with SALT  good mix of MSTO, RGB and Blue giant stars.

  31. Simulated 2” SALT seeing – stars of interest outside fused core will be photometered in each FP channel image w/ standard crowded field code

  32. SOAR GS long slit spectra to estimate systematics Two slits were observed by Bart & Josh in Oct 2012 CINDERS fov 3 probes spaced 100 arcsec apart 5040 3736 4160 Bt5049/5040 4428 5049 4670 5218 101.5deg 92.5deg

  33. Presentation outline • GCs are good indicator of a galaxy’s major formation history - Globular clusters in top-down & bottom-up galaxy formation • Color bimodal distribution. Problem: age/metallicity degeneracy (Worthey+94) - Observation of globular cluster population in a typical galaxy • How to break this degeneracy with index/index plot - Absorption spectral indices + Simple Stellar Population (SSP) models (Lick Indices + MILES library ) • Fabry-Perot (FP) technique to obtain Lick Indices - Advantages if systematics can be controlled == This presentation == • Reason for choosing NGC 1850 - Spatially extended, bright mix of stars. • Preliminary SALT & SOAR results - What has been done since spring - Challenges & Systematics • Next steps - Immediate tasks - Expected Publications

  34. Since our last meeting in January: Reduced SALT data. (6 LR, 41 MR exposures) - This is due for a redo as I applied the same wavelength flat field to all images. - Talked to SALT “Tim” about the degradation of PSF for 2nd half of the images*. Proposal submitted to retake those images in the Fall. - Figured out how to do wavelength calibration. There is a significant shift in wavelength that affects my results.*Learned IRAF Daophot package and extracted stellar fluxes from 47 frames - 70 good psf stars were selected on the first image and used on subsequent images. (Nebulosity can make this a problem) - 4 iterations of psf fitting before flux measurements Automated the Daophot procedure with Pyraf scripts - Average seeing was measured for each frame. - Coordinate transformations were found with python code “ALIPY 2.0”. - Stars were matched across the images after Daophot was done. The product was a 3D data cube - Stars from Hubble image / HR diagram were found and matched. - Comparison plots between the SOAR LS and SALT etalon spectra were made.* Documented every step in Mathematica notebook. *will be shown in later slides

  35. SALT Exposures(show video)Change contrast in ATI CCC if too dimGhostNebulosity (present in the sky spectra)

  36. {1914,836,467,299,269,229,191,139,135,115,99,86,110,71,81,80,71,58,75,64,68,66,60,45,64,56,53,45,48,62,49,39,61,50,51,58,68,72,81,84,85,96,104,127,147,223,670}{1914,836,467,299,269,229,191,139,135,115,99,86,110,71,81,80,71,58,75,64,68,66,60,45,64,56,53,45,48,62,49,39,61,50,51,58,68,72,81,84,85,96,104,127,147,223,670} Total 670 stars detected in SALT’s 8’x8’ field. Not all are positive detections and not all belong to NGC1850. What are those 223 “stars” that are missing in one frame?

  37. SOAR & SALT spectra(Hand out PDF)Go over the plots firstShow the first frame on the previous video on the projectorThe “Dip” at left sideWavelength offset Discrepancy in the sky continuum level

  38. The “Dip” at the left side is apparent in the summed flux as well. The Hbeta absorption feature is not as apparent (probably) due to wavelength calibration error / line broadening

  39. Order confusion: Order blocking filter does not filter out adjacent orders.

  40. #88 86s LR All subsequent Daophot parameters are based on this image

  41. #88sub 86s LR The star subtracted image looks pretty good

  42. #95 86s MR However parameters should have been changed because now it’s a MR image instead of a LR image.

  43. #95sub 86s MR Subtraction is poor, this can be one of the causes for “dip” at the shorter wavelength on the SED vs Wavelength plot

  44. #108 86s MR Image at the peak flux

  45. #108sub 86s MR Subtraction improved

  46. #120 86s MR Nebulosity kicks in at #120.fits or #32 on the pdf plot

  47. #120sub 86s MR More could be done to optimize daophot parameters

  48. #135 86s MR Coma kicked in half way through and was apparent at the end. Softer image: Spherical aberration caused by degradation in primary mirror alignment Coma: Misalignment between primary and secondary mirror

  49. #135 86s MR Zoomed in Coma kicked in half way through and was apparent at the end. Softer image: Spherical aberration caused by degradation in primary mirror alignment Coma: Misalignment between primary and secondary mirror

  50. #135sub 86s MR Subtraction looks fine due to good iterative PSF fitting

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