1. Dust in edge-on spiral galaxies from the J-band of the 2MASS Large Galaxy Atlas Angelos Misiriotis (1) and Manolis Xilouris (2) (1) University of Crete, Department of physics (2) National observatory of Athens

2. Motivation (a case for “optical” detection of dust) Motivation (a case for “optical” detection of dust) Optical studies are coplementary to FIR observations Require less exotic equipment Take advantage of huge archaives Constrain the emissivity

3. Why edge-on ? Image from the 2MASS L.G.A. Jarrett T. H., Chester T., Cutri, R. Schneider, S. E. Huchra, J. P., 2003, AJ, 125, 525

4. Figure from: Bosma A., Byun Y., Freeman K. C. Athanassoula E., 1992, ApJ, 400, 21 In the J Band (τ ~ 0.1) The edge-on line of sight reaches the center The dust lane is still visible Why J-band ?

5. Why the 2MASS, Large Galaxy Atlas (*) ? (*)Jarrett, T. H.; Chester, T.; Cutri, R.; Schneider, S. E.; Huchra, J. P., 2003AJ....125..525J Large homogenious sample Easily available Good pilot before spending months for deeper observations Out of the LGA 28 edge-on galaxies were selected for this study.

6. The Model A stellar bulge (de Vaucoulers) Xilouris E. M., Byun Y. I., Kylafis N. D., Paleologou E. V., Papamastorakis, J., 1999, A&A, 344, 868

7. The Model A stellar bulge (de Vaucoulers) A stellar exponential disk Xilouris E. M., Byun Y. I., Kylafis N. D., Paleologou E. V., Papamastorakis, J., 1999, A&A, 344, 868

8. The Model A stellar bulge (de Vaucoulers) A stellar exponential disk An exponential dust disk Xilouris E. M., Byun Y. I., Kylafis N. D., Paleologou E. V., Papamastorakis, J., 1999, A&A, 344, 868

9. Textbook Cases (7/28 galaxies ) Textbook Cases (7/28 galaxies ) Observation Model

10. Passable Cases (8/28 galaxies ) Passable Cases (8/28 galaxies )

11. Impossible Cases (5+8/28) Impossible Cases (5+8/28) Which leaves us with 15/28 galaxies to draw some results on the dust properties.

12. Results Optical depth as a function of M K Results Optical depth as a function of M K

13. Results Optical depth as a function of dust mass Results Optical depth as a function of dust mass

14. Conclusions J-Band is ideal for optical studies of dust in edge-on galaxies provided a high resolution. Larger spirals exhibit higher face-on optical depth. There might be a threshold of the optical depth in normal spiral galaxies.