The Virgo Stellar Stream Third Chilean Advanced School in Astrophysics The Virgo Stellar Stream The Virgo Stellar Stream: a win- win thesis project... Sonia Duffau E. Maria Teresa Ruiz, Robert Zinn, Kathy Vivas, Giovanni Carraro, René Méndez Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Outline Tidal tails and Dark matter VSS, VOD or Sgr. ? Martinez-Delgado views v/s our data Discussion and work ahead 10 enero 2007 Third Chilean Advanced School in Astrophysics Outline Sonia Duffau E.

Tidal streams, Cosmology and DM Halo Third Chilean Advanced School in Astrophysics Tidal streams, Cosmology and DM Halo -Ultimate goal: to infer the formation process of the Milky Way from the properties of the present fossil records. -Find (or not) the predicted merger remnants from the hierarchical build-up view of our Galaxy. 10 enero 2007 Third Chilean Advanced School in Astrophysics Intro to subject Sonia Duffau E.

Tidal tails and Dark matter Third Chilean Advanced School in Astrophysics Tidal tails and Dark matter Study of tidal tails by means of: Observations Comparison with models Example model of Sgr. : Law’s models http://astsun.astro.virginia.edu/~srm4n/Sgr Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Tidal Debris of the Sagittarius Dwarf Spheroidal This webpage is intended to serve as a companion resource to the discoveries recently presented by Majewski and collaborators in the following suite of 6 papers: A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy Paper I: Morphology of the Sgr Core and Tidal Arms (Majewski et al. 2003, ApJ, 599, 1082) Paper II: Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold Sagittarius Tidal Stream (Majewski et al. 2004a, ApJ, 128, 245) Paper III: Constraints on the Flattening of the Galactic Halo (Johnston, Law, & Majewski 2004, ApJ Submitted, astro-ph/) Paper IV: Modeling the Sagittarius Tidal Tails (Law, Johnston, & Majewski 2004, ApJ Submitted, astro-ph/) Paper V: Radial Velocities of Leading Debris (Majewski et al. 2004b, in preparation) Paper VI: Globular Cluster Associations (Majewski et al. 2004c, in preparation) Sep. 24 press release on Paper I The following resources may be of interest to those who are interested in studying the Sgr dwarf and its tidal streams. These are all the work of David R. Law.: A description of the Sgr longitudinal coordinate system (Paper I). C++ code to convert from Galactic coordinates into the Sgr coordinate system. Full spatial data for the best fit Sgr models (Paper IV). 3D "flyaround" movie of the best fit Sgr models. Click! Copyright Notice: Please note that all papers are the copyright of the respective journals in which they are published. Any publications wishing to use data available on this website should acknowledge this website as the source for that data. http://astsun.astro.virginia.edu/~srm4n/Sgr Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Best-fitting Sgr disruption models Simulations are realized using 10^5 particles in a self-consistent field code (see Paper IV). These files have 16 columns of data as given below. All distances are in kpc, all velocities in km/s, and all angular measurements are in degrees. Lambda_sun: orbital longitude. Beta_sun: orbital latitude. l: Galactic longitude. b: Galactic latitude. X_GC: Standard left-handed Galactocentric Cartesian coordinate. Y_GC: Standard left-handed Galactocentric Cartesian coordinate. Z_GC: Standard left-handed Galactocentric Cartesian coordinate. X_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system. Y_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system. Z_sun: Right-handed heliocentric Cartesian coordinate in the Lambda_sun system. U: Galactic U velocity (left-handed frame). V: Galactic V velocity (left-handed frame). W: Galactic W velocity (left-handed frame). d: Heliocentric distance. vgsr: Radial velocity relative to the Galactic Standard of Rest (NB: GSR, not LSR). Pcol: "Color", or unbound era of simulated particle. Data files are provided below for the three models discussed in Paper IV (oblate,spherical, and prolate Galactic halo models). Oblate (q=0.9) model. Spherical (q=1.0) model. Prolate (q=1.25) model. Up http://astsun.astro.virginia.edu/~srm4n/Sgr Sonia Duffau E.

Third Chilean Advanced School in Astrophysics A bit of history ... VSS Sgr First discovered in Carbon stars by Ibata, 1994. All sky view by means of M giants from the 2MASS survey (Majewski et al. 2003) Vivas´s thesis finds it on QUEST data, 2000-2001 VSS QUEST detects over-density in RR Lyrae towards Virgo (12.4 hr clump) SDSS detects MS turnoff (S297+63+20.0) QUEST/Yale/ Calan does first spectroscopic follow up (VSS) SDSS constructs first density maps (VOD) towards Virgot Sgr. Radial distribution plot for all QUEST data 10 enero 2007 Third Chilean Advanced School in Astrophysics Intro to VSS, VOD and Sgr. Sonia Duffau E.

Spectrosocpy of QUEST RR Lyrae variables: The new Virgo Stellar Stream Third Chilean Advanced School in Astrophysics Spectrosocpy of QUEST RR Lyrae variables: The new Virgo Stellar Stream Fig. 2 RRLy and BHBs in the area Location of 12.4 hr clump Fig. 1 Duffau et al. 2006, ApJ, 636, L97-L100 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Results Metallicity <[Fe/H]> = -1.86 dex σ = 0.4 dex σ(int) = 0.08 dex Radial velocity <Vgsr> = 99.8 km/s σ = 17.3 km/s <Vgsr> = 83.2 km/s σ = 24.5 km/s σ(meas) = 18.8 km/s Overdensity of RRLy Non-gaussian velocity distribution Suspect Stellar Stream from a disrupted Dwarf galaxy Located in the direction of Virgo New Virgo Stellar Stream (VSS) More spectroscopic observations for january 2007! 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

SDSS density maps and the VOD Third Chilean Advanced School in Astrophysics Contrast with Galaxy model Virgo overdensity Juric et al., astro-ph /0510520 Astro-ph paper by SDSS identifying overdense extended feature in direction of Virgo 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Sgr. falling down the plane? Third Chilean Advanced School in Astrophysics Sgr. falling down the plane? 10 enero 2007 Third Chilean Advanced School in Astrophysics Intro to astro-ph Sonia Duffau E.

Sgr. Debris towards Virgo the physical link Third Chilean Advanced School in Astrophysics Sgr. Debris towards Virgo the physical link Oblate model by Law Even older passages Three orbits ago Two orbits ago Unbound durina the last orbit Martinez-delgado et al. 2006, astro-ph/0609104 Intro to M-D views 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Martinez-Delgado oblate model Third Chilean Advanced School in Astrophysics Martinez-Delgado oblate model Particles unbound only 2.5 Gyrs ago VOD stars consistent with model Sun 10 enero 2007 Third Chilean Advanced School in Astrophysics M.D. astro-ph Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Oblate Prolate 3-D view Model Low density=blue High density = red VSS in dark box VOD in white box Yellow point is the sun 10 enero 2007 Third Chilean Advanced School in Astrophysics M.D astro-ph Sonia Duffau E.

Artist’s view of the problem Third Chilean Advanced School in Astrophysics Artist’s view of the problem Oblate Prolate 10 enero 2007 Third Chilean Advanced School in Astrophysics M. D. conference PPT Sonia Duffau E.

Third Chilean Advanced School in Astrophysics Is it all Sagittarius ? Oblate Prolate VSS Duffau et al. (2006) Leading arm Leading arm Trailing arm 10 enero 2007 Third Chilean Advanced School in Astrophysics M-D comparison Sonia Duffau E.

Third Chilean Advanced School in Astrophysics So what is it then ? In the case of VOD it seems clear that it is unlikely unrelated to Sgr. but SDSS has no velocity info yet… In the case of the VSS if it is related to Sgr. ,it is related to stars from an old passage of the satellite still undetected, if not, it is a completely new event! Any of these cases makes this a great result, and valuable data for near field cosmology 10 enero 2007 Third Chilean Advanced School in Astrophysics Discussion Sonia Duffau E.

VLT results and Virgo paper Third Chilean Advanced School in Astrophysics VLT results and Virgo paper For our latest results on Sagittarius and the Virgo paper please look for poster 14 on the panels !!! VLT spectroscopy of RR Lyrae stars in the Sagittarius northern tidal stream S. Duffau (Universidad de Chile), M. T. Ruiz (Universidad de Chile), R. Zinn (Yale University) & A. K. Vivas (CIDA institute) Abstract: We present VLT spectroscopy of 13 RR Lyrae variables from the QUEST survey that lie in the leading arm of the tidal stream from Sagittarius dSph galaxy. We observed these stars to measure their radial velocities and metal abundances and to complete a sample of stars from the overdensity detected by QUEST in this area of the sky. The full sample contains 42 stars, 29 observed with VLT and 13 observed with GEMINI, we report here the results from the VLT observations so far. We conclude that the new stars and stars reported before by Vivas, Zinn and Gallart, 2005, are consistent with belonging to Sgr. We discuss the importance of the final third of the sample, the GEMINI targets, which will provide important constrains on models of the Sgr streams that assume different dark matter halo shapes. Sgr. Introduction: A detailed study of the Sgr. tidal tails may help us understand Galaxy formation in many ways. Sgr is the prototypical case of the process of tidal disruption and galaxy merger, providing insight on a process that might be responsible for the formation of the luminous halos of galaxies like our own. The stellar populations along the tails might have evolved under the presence of the strong tidal forces, this can be revealed by comparing different stellar populations at different location on the streams. Finally the streams have been proposed as possibly powerful tools to study the shape of the Milky Way´s potential, which at large galactocentric distances (like the ones involved in this study), may be dominated by the shape of the dark matter halo (DM). Theoretical models of Sgr tidal disruption under assumptions of different DM halo shapes differ on small scales. The precisions that are necessary to distinguish between these small differences observationally are achieved with RR Lyrae stars because they are excellent standard candles providing their location in space very precisely, much more than with other tracers. The ultimate goal of this research is to test models of the streams that assume different shapes for the gravitational potential of the MW, using both the high positional accuracy of RR Lyrae stars and their radial velocities. For the moment we have studied two thirds of the intended sample using VLT. GEMINI data on the last third will follow. Fig. 1: radial plot of RR Lyrae from QUEST 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Third Chilean Advanced School in Astrophysics 10 enero 2007 Third Chilean Advanced School in Astrophysics

Spatial distribution of VSS Third Chilean Advanced School in Astrophysics LARIM 2005 Pucón 12-16 December Spatial distribution of VSS Region of sky with excess of stars with respect to control field Mag interval ~19.5 < g < 20.5 Found in at least 106 deg2 of the searched area Closer to the Sun Searched Zone 1 Zone 2 10 enero 2007 Third Chilean Advanced School in Astrophysics . Sonia Duffau E.

Extended Search of VSS using SDSS Third Chilean Advanced School in Astrophysics Extended Search of VSS using SDSS Feature extends at least 106 deg2 on the sky 2σ Poisson excess threshold Pal 5 Virgo Central region Less prominent detection 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Velocity distribution Third Chilean Advanced School in Astrophysics Velocity distribution Central Region Distribution is non-Gaussian Main peak has <Vgsr> = 99.8 and σ = 17.3 km/s Average error=18.8 km/s Evidence for a New Stellar Stream, the VSS Possibility of more than one group will be explored Main Peak Outside central region 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

Sample Star distribution Third Chilean Advanced School in Astrophysics BHBs from Sirko et al. (2004) AJ 127, 899. Sample Star distribution Central region Circles= QUEST RRLy Triangles=BHBs Small symbols have no spectral information Dashed box=¨Central region¨ Solid=possible members of a new Stellar Stream 1.0-1.4 RRLy expected, 8 found! 10 enero 2007 Third Chilean Advanced School in Astrophysics Sonia Duffau E.

QUEST RRLy survey and the 12.4 hr clump Third Chilean Advanced School in Astrophysics QUEST RRLy survey and the 12.4 hr clump Plot showing the ¨12.4 hr clump¨ selected for spectroscopic follow-up Also identified by Newberg et al. 2002. A. K. Vivas, PhD Thesis, Yale University, 2001 Newberg et al. 2002 ApJ 569, 245 Sgr Pal 5 10 enero 2007 Third Chilean Advanced School in Astrophysics RA vs. Heliocentric distance for QUEST RRLy zone 1 targets Sonia Duffau E.