Tidal Streams in the Milky Way (and M31)

Jorge Peñarrubia (University of Victoria, Canada)

& David Martinez Delgado

(IAC, Spain)

22th of June 2006 Valencia

1-Tidal streams

Tidal streams result from the disruption of stellar systems

They provide information on:1. The Milky Way potential on large distance scales (20 -- 100 kpc)2. The mass and orbit of the progenitor3. The stellar evolution within the progenitor4. The formation of spiral galaxies

Tidal streams represent a powerful tool to testcosmological predictions

2- The Sgr stream. Status

The Sgr stream was the first major evidence that the MW may have formed through hierarchical infall of smaller systems

Current theoretical picture

SDSS data

qh=0.8

qh=1.4

Y

Z

R

The Sgr stream may be passing close (<5 kpc) to the solar neighbourhood.

An unvaluble target for

RAVE (Radial Velocity survey)

Future experiments aiming to detect dark matter emission

The Virgo over-density

Martinez-Delgado, Peñarrubia et al.(in prep.)

3- The Monoceros Stream

In contrast to the Sgr stream, the Mon stream appears to be located on low latitudes. First detected by Newberg et al. (2002) with SDSS data.

QuickTime™ and aCinepak decompressor

are needed to see this picture.

By collecting all available observational data, Peñarrubia et al. (2005) constrained the progenitor orbit: e=0.100.05 ; i=25±5 deg.

Theoretical models predict a streamage < 3 Gyr

4- M31 … twin sister of the Milky Way?

M31 has a mass and structure similar to the Milky Way. Did M31 follow a similar formation process?

M31 also suffered a recent merger of a massive, highly eccentric satellite galaxy moving on an eccentric orbit, visible today in form of the Giant Stream

Sgr model

Recently, Ibata et al. (2005) detected a giant extended disc (R<80 kpc) which might be the remants of a low-latitude, low-eccentricity merger

(similar to the Mon stream’s progenitor)

Peñarrubia, McConnachie & Babul (2006)

QuickTime™ and aBMP decompressor

are needed to see this picture.

Mon stream model