# Presentation: 411578

##                      SEGUE:

- l,b = 110,-8

-                      SEGUE:
-       Sloan Extension for Galactic
-      Understanding and Exploration
- Program to obtain imaging and spectra
- of a quarter of a million stars in our
- Milky Way.

## KV

- 8 kpc

- G

- MSTO/F

- BHB/BS

- K III

- SEGUE uses stellar probes of increasing
- absolute brightness to probe
- increasing distances in the disk, thick
- disk and Milky Way halo.

- d < 1 kpc

- d < 6 kpc

- d < 15 kpc

- d < 50 kpc

- d < 100 kpc

- Other spectroscopic surveys will not probe as deep,
- for instance, Blue Horizontal Branch Stars (BHBs) from a
-  survey with V< 12 are from a volume within 1.5 kpc of the sun.

- r = 1.5kpc

- Streams and outer halo stars

- Inner and outer halo stars

- thin, thick
- disk stars

## KV

- 8 kpc

- G

- MSTO/F

- BHB/BS

- K III

- SEGUE uses stellar probes of increasing
- absolute brightness to probe
- increasing distances in the disk, thick
- disk and Milky Way halo.

- d < 1 kpc

- d < 6 kpc

- d < 15 kpc

- d < 50 kpc

- d < 100 kpc

- Other spectroscopic surveys will not probe as deep,
- for instance, Blue Horizontal Branch Stars (BHBs) from a
-  survey with V< 12 are from a volume within 1.5 kpc of the sun.

- r = 1.5kpc

- Streams and outer halo stars

- Inner and outer halo stars

- thin, thick
- disk stars

## 50000 K

**O**
**B**
**A**
**F**
**G**
**K**
**M**
**L**
**T**

**u     g     r     i     z**

- 20000 K
- 10000 K
-   7500 K
-   5500 K
-   3500 K
-   2000 K
-   1200 K
-     900 K

- 20
- 10
-   5
-   2
-   1
-  0.7
-  0.4
-  0.1
-  0.05

- Mass (Solar)

- Temperature

## The Stellar Sequence

- O
-        B
-                                 A
-                                            F
-                                                       G
-                                                                     K (dwarf)
-                                                                                        M (dwarf)
- White Dwarf
-          Hotter

- K Giant

- M Giant

- BHB

- Stellar Color

- Cooler

- Brighter

- Main Sequence

- Color
- Degeneracy

## Stars in the field of Globular Cluster Pal 5

- g'

- g'-r'

- Horizontal Branch

- Blue
- Stragglers

- Red Giant Branch

- Turn off

- Main Sequence

## Stars may be 'field' stars at a variety

- of (unknown distances), or part
- of a 'cluster' at 'one' distance.

## 11 kpc

**Galactic**
**Center**

**Stars in**
**the smooth**
**“****spheroid”**
**population**

**Pal 5 globular cluster**

**Sagittarius dwarf tidal stream**

**Sagittarius dwarf**
**Tidal stream**

**Sun**

## ARC

**SDSS Data**

**INT Data**

**Ring properties:**
**100 million to **
**half a billion stars, **
**about the size **
**of the SMC**
**Ten times thicker **
**than the Galaxy’s**
**thin disk**

## Slide 10

## Vel ~ const(d)

- Implies
- There must
- be some mass
- out here!
- But I can't see it!
- This is
- “Dark Matter”

## Nothing out here

- implies
- Keplerian fall off
- starting at edge
- of Galactic disk.

- Vel ~ 1/(sqrt[d])

- But...

## Data from Begeman 1989  for the spiral galaxy NGC 3198

- Data for a Galaxy like the Milky Way, in HI Gas.

- Visible edge of Galaxy
-              HI gas in rotation

## Thus, we have both a polar ring tidal tail (Sag.)

- and a planar ring (arc) tidal structure (Monoceros),
- (and who knows what else) SDSS-II/SEGUE will
- continue to look....
- Both used together, with added kinematic information,
- will help us constrain the potential and distribution
- of the dark matter which apparently surrounds
- the Milky Way.

- Conclusion:

## Vel ~ const(d)

- Implies
- There must
- be some mass
- out here!
- But I can't see it!
- This is
- “Dark Matter”