AAS 204th Meeting, June 2004
Session 15 Diffuse Media Galactic and Intergalactic
Oral, Monday, May 31, 2004, 10:00-11:30am, 601

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[15.06] Radial Extinction in Spiral Disk from the numbers of background galaxies.

B.W. Holwerda (Kapteyn Institute/STScI), R.A. Gonzalez (UNAM), R.J. Allen (STScI), P.C. van der Kruit (Kapteyn)

Dust extinction can be determined from the number of background field galaxies seen through the disk of a foreground galaxy. In order to calibrate these numbers, Gonzalez (1998) developed the "Synthetic Field Method''. The synthetic fields are a HDF field, extincted with as certain value, added to the original field of the spiral disk. Field galaxy counts from these tell us the relation between extinction and number of field galaxies, calibrated for each field. Therefore, with the SFM, the average extinction for a certain area in the foreground disk can be obtained from the number of field galaxies.

We have applied an automated Synthetic Field Method (Holwerda 2004) to a set of 30 archival deep HST/WFPc2 fields of spirals. From the numbers of field galaxies in these fields we derive the average extinction with radius in spiral disks for different Hubble types.

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