Application of STREAMFINDER onto ESA/Gaia DR2 w/ Rodrigo A. Ibata - - PowerPoint PPT Presentation

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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

SLIDE 1

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

SLIDE 2

Stellar Streams

Pal 5 stream. Discovered by

Odenkirchen et al. (2001). This map was

created by Bernard et al (2016)

SLIDE 3

Stellar Streams

Pal 5 stream. Discovered by

Odenkirchen et al. (2001). This map was

created by Bernard et al (2016)

Orbital Structure of Streams

SLIDE 4

Stellar Streams

Malhan, Ibata & Martin (2018). ZEA projection of the Galactic sky. The

plot was created using galstreams package (Mateu et al 2017)

>40 Milky Way Streams (SDSS, Pan-STARRS1, DES, ATLAS…)

SLIDE 5

STREAMFINDER

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

Malhan & Ibata (2018)

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STREAMFINDER

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

Malhan & Ibata (2018)

SLIDE 7

STREAMFINDER

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

Malhan & Ibata (2018)

SLIDE 8

STREAMFINDER

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)

Malhan & Ibata (2018)

SLIDE 9

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)

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STREAMFINDER

Malhan & Ibata (2018)

GAIA-like ERRORS PERFECT STREAM

Testing algorithm with N-body simulated ~Pal-5 stream

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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.

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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 Data orbit Perfect orbit

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STREAMFINDER

Malhan & Ibata (2018)

Ldatum = Lkinematics + LLF + Lcontinuity

Log-likelihood of a star being associated with a stellar stream.

Data-orbit comparison (given the observed errors) Luminosity Function criteria Stream continuity criteria

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STREAMFINDER

Malhan & Ibata (2018)

Ldatum = Lkinematics + LLF + Lcontinuity

Log-likelihood of a star being associated with a stellar stream.
L acts as ``weight’’ for every star used to obtain stream density plot

Data-orbit comparison (given the uncertainties) Luminosity Function criteria Stream continuity criteria

SLIDE 15

STREAMFINDER

Malhan & Ibata (2018)

Stream output – log-likelihood density plot

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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)

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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

using different SSP models

SSP 1 SSP 2 SSP 3

SLIDE 18

MW Stellar Stream map from Gaia DR2

Malhan, Ibata & Martin (2018)

Gaia DR2 dataset

|b|>30 ◦
GCs and DGs

masked

STREAMFINDER

results…?

1. Find GC streams (narrow and cold)
2. Dehnen & Binney (1998)
3. 7 SSP [Fe/H]=[-1.0, -2.2], Age=10Gyrs

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GD-1

Sagittarius Stream Gaia-1* Gaia-2* Gaia-3*

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GD-1

Sagittarius Stream Gaia-1* Gaia-2* Gaia-3*

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Sagittarius Stream Jhelum Indus Gaia-4* LMC SMC

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Sagittarius Stream Jhelum Indus Gaia-4* LMC SMC

SLIDE 23

Phase-space-luminosity coherence of the structures. Malhan et al (2018)

Observations Orbital Solutions

SLIDE 24

Testing the phase-space-luminosity coherence of the structures. Malhan et al (2018)

SLIDE 25

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

bservations (Koposov et al 2010)

STREAMFINDER solutions

STREAMFINDER BLOBFINDER (find blob of stars – star clusters and

dwarf galaxies)

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