1. Bershady Verheijen Westfall Martinsson Swaters Andersen
The Disk-Mass Survey
Bershady Verheijen Westfall Martinsson Swaters Andersen
goals: - obtain radial surface-density profiles Σ(r) of galaxy disks
- determine M/L of stellar populations in disks
- break disk-halo degeneracy in rotation curve decompositions
- get ρDM(r)
method: measure vertical stellar velocity dispersion σ
data: R≈10 spectroscopy of MgIb & CaII at ≤ 3 R (μ =24.5)
two custom-built wide-field fiber-based IFUs (SparsePak, P-Pak)
sample: ∼40 nearly face-on (incl=25°- 35°), kinematically regular spirals
range in morphology, mass, color, surface brightness, SF rate ... z 4
disk B

2. SparsePak P-Pak UW - Madison AIP - Potsdam 3.6m WIYN, Kitt Peak
71"x72" field of view
82 fibers (4.7" ∅)
75 science, 7 sky
R≈ (Hα, MgIb, CaII)
3.5m CAHA, Calar Alto
64"x74" field of view
382 fibers (2.7" ∅)
331 science, 36 sky, 15 calib.
R≈ (MgIb, Hα/Hβ/Hγ)

3. IFU spectroscopy : azimuthal averaging to gain S/N
UGC 6918
HST/WFPC-2
P-Pak : MgIb
SparsePak : Hα (3-point dither)
MgIb, CaII

4. Sample & Strategy optical (SDSS) 400 galaxies pre-selected from UGC
Hα velocity fields (SparsePak)
8 micron (Spitzer)
50 kpc
2 arcmin
Sample & Strategy
400 galaxies pre-selected from UGC
type, size, inclination, visually inspected
non-interacting, non-barred
Hα velocity fields of 130 randomly chosen
spirals
Subsample of 40 spirals with
- regular Hα velocity fields
- stellar kinematics (MgIb, CaII)
- optical imaging (U,B,V,R,I)
- near-IR imaging (J,H,K)
- Spitzer imaging (4.5,8,24,70μm)
- HI & 1.4 GHz continuum (ongoing)

5. photometry
Hα velocity field
stellar VF & LOSVD
U6918

6. Ongoing work & some results
Important (and time-consuming) issues:
Registration: refine the pointings of the dithered Hα velocity field observations
Flexure issues (shifts, scale differences & rotations)
Decompose vel.disp ellipsiod (σr, σφ, σz)
Westfall et al (astro-ph/ )
Careful error propagation and understanding the error budget