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Stellar Stream Map of the Milky Way Halo : Application of STREAMFINDER Onto ESA/Gaia DR2 W/ Rodrigo A

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Stellar Stream Map of the Milky Way Halo : Application of STREAMFINDER Onto ESA/Gaia DR2 W/ Rodrigo A Stellar Stream map of the Milky Way Halo : Application of STREAMFINDER onto ESA/Gaia DR2 w/ Rodrigo A. Ibata and Nicolas F. Martin @kmalhan07 Khyati Malhan PhD Student Supervisor: Dr. Rodrigo Ibata Stellar Streams Pal 5 stream. Discovered by • Odenkirchen et al. (2001). This map was created by Bernard et al (2016) Stellar Streams Orbital Structure of Streams Pal 5 stream. Discovered by • Odenkirchen et al. (2001). This map was created by Bernard et al (2016) Stellar Streams >40 Milky Way Streams (SDSS, Pan-STARRS1, DES, ATLAS…) • Malhan, Ibata & Martin (2018). ZEA projection of the Galactic sky. The plot was created using galstreams package (Mateu et al 2017) STREAMFINDER Malhan & Ibata (2018) Maximize stream detection by: • Using all the prior information about the stellar stream ( analyzing phase-space-color-magnitude distribution simultaneously) • This is possible with Gaia DR2 STREAMFINDER Malhan & Ibata (2018) Maximize stream detection by: • Using all the prior information about the stellar stream ( analyzing phase-space-color-magnitude distribution simultaneously) • This is possible with Gaia DR2 Best way to detect stream : LOOK ALONG THE ORBITS STREAMFINDER Malhan & Ibata (2018) Maximize stream detection by: • Using all the prior information about the stellar stream ( analyzing phase-space-color-magnitude distribution simultaneously) • This is possible with Gaia DR2 Best way to detect stream : LOOK ALONG THE ORBITS STREAMFINDER Malhan & Ibata (2018) Maximize stream detection by: • Using all the prior information about the stellar stream ( analyzing phase-space-color-magnitude distribution simultaneously) • This is possible with Gaia DR2 Best way to detect stream : LOOK ALONG THE ORBITS. stream members contained in a 6D hypertube and its 6D volume ~ f(σw, σv, torbit) STREAMFINDER Malhan & Ibata (2018) Testing algorithm with N-body simulated stream • Simulated a globular cluster stream in a realistic galactic model (Dehnen & Binney 1998) • Retained only 50 objects in the stream, ΣG =33 mag arcsec-2 (faint stream) • Retained only 4D phase-space information – l , b, μl ,μb (with errors) vrad and ω information was deleted. • Convolved Gaia like errors in proper motions. • Also assigned a SSP model to the stream of ([Fe/H], Age)= (-1.5, 10 Gyr) STREAMFINDER Malhan & Ibata (2018) Testing algorithm with N-body simulated ~Pal-5 stream PERFECT STREAM PERFECT like ERRORS like - GAIA STREAMFINDER Malhan & Ibata (2018) • Stream (50 stars) + GUMS (330,000 stars) = Data (0.015% stream stars) • vrad and ω information was deleted. Convolved Gaia like errors. STREAMFINDER Malhan & Ibata (2018) Orbit sampling • Blindness and uncertainty in stellar phase-space position. • Sample orbits in: a) distance space (3 solutions based on SSP model) b) proper motion space (-3σ to +3σ) c) vrad space (s.t. vtotal< vescape) • ~30,000 orbits for every datum. Sampled orbits Perfect orbit Data orbit STREAMFINDER Malhan & Ibata (2018) • Log-likelihood of a star being associated with a stellar stream. Ldatum = Lkinematics + LLF + Lcontinuity Data-orbit comparison Luminosity Stream continuity (given the observed errors) Function criteria criteria STREAMFINDER Malhan & Ibata (2018) • Log-likelihood of a star being associated with a stellar stream. Ldatum = Lkinematics + LLF + Lcontinuity Data-orbit comparison Luminosity Stream continuity (given the uncertainties) Function criteria criteria • L acts as ``weight’’ for every star used to obtain stream density plot STREAMFINDER Malhan & Ibata (2018) • Stream output – log-likelihood density plot STREAMFINDER Malhan & Ibata (2018) Multiple stream case : • Age = 9-10 Gyrs • [Fe/H] = -1.5 to -2.5 • 50 stars per stream • Surface brightness ~ 33 mag arcsec-2 (very faint) STREAMFINDER Malhan & Ibata (2018) Multiple stream case : SSP 1 • Age = 9-10 Gyrs • [Fe/H] = -1.5 to -2.5 • 50 stars per stream • Surface brightness SSP 2 ~ 33 mag arcsec-2 (very faint) • STREAMFINDER using different SSP models SSP 3 MW Stellar Stream map from Gaia DR2 Malhan, Ibata & Martin (2018) results…? Gaia DR2 dataset • |b|>30 ◦ STREAMFINDER • GCs and DGs masked 1. Find GC streams (narrow and cold) 2. Dehnen & Binney (1998) 3. 7 SSP [Fe/H]=[-1.0, -2.2], Age=10Gyrs Gaia-3* Gaia-2* Gaia-1* GD-1 Sagittarius Stream Gaia-3* Gaia-2* Gaia-1* GD-1 Sagittarius Stream Gaia-4* Jhelum Sagittarius Stream SMC Indus LMC Gaia-4* Jhelum Sagittarius Stream SMC Indus LMC Observations Orbital Solutions Phase-space-luminosity coherence of the structures. Malhan et al (2018) Testing the phase-space-luminosity coherence of the structures. Malhan et al (2018) STREAMFINDER Malhan & Ibata (2018) Main advantages of the algorithm : • Detection of v. faint structures, even if on complex orbits • Completing the 6D DF(x,v) of detected stellar streams -useful in the context of galaxy formation . GD-1 stream observations (Koposov et al 2010) STREAMFINDER solutions • STREAMFINDER BLOBFINDER (find blob of stars – star clusters and dwarf galaxies) .
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