Abstract
This paper considers some effects of foreground Galactic gas on radiation received from extragalactic objects, with an emphasis on the use of the 21cm line to determine the total N HI . In general, the opacity of the 21cm line makes it impossible to derive an accurate value of N HI by simply applying a formula to the observed emission, except in directions where there is very little interstellar matter. The 21cm line can be used to estimate the likelihood that there is significant if H 2 in a particular direction, but carries little or no information on the amount of ionized gas, which can be a major source of foreground effects. Considerable discussion is devoted to the importance of small-scale angular structure in HI, with the conclusion that it will rarely contribute significantly to the total error compared to other factors (such as the effects of ionized gas) for extragalactic sight lines at high Galactic latitude. The direction of the Hubble/Chandra Deep Field North is used as an example of the complexities that might occur even in the absence of opacity or molecular gas.
The National Radio Astronomy Observatory is operated by Associated Universities, Inc., under a cooperative agreement with the National Science Foundation
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Balucinska-Church, ML, & McCammon, D. 1992, ApJ, 400, 699
Barnes, D.G., & Nulsen, RE.J. 2003, MNRAS, 343, 315
Bohlin, R.C., Savage, B.D., & Drake, IE 1978, ApJ, 224, 132
Boulanger, E, Bernard, J-R, Lagache, G., & Stepnik, B., 2001, “The Extragalactic Infrared Background and its Cosmological Implications”, IAU Symp. 204, ed. M. Harwit & M. G. Hauser, ASP, p. 47
Deshpande, A.A. 2000, MNRAS, 317, 199
Deshpande, A.A., Dwarakanath, K.S., & Goss, W.M. 2000, ApJ, 543, 227
Dickey, J.M., & Brinks, E., 1993, ApJ, 405, 153
Dickey, J.M., & Lockman, F.J., 1990, ARAA, 28, 215 (DL90)
Dickey, J.M., McClure-Griffiths, N.M., Stanimirovic, S., Gaensler, B.M., & Green, A.J. 2001, ApJ, 561, 264
Dickey, J.M. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A.R. Taylor,
T.L. Landecker, & A.G. Willis, p. 248
Elvis, M., Lockman, F.J., & Fassnacht, C. 1994, ApJS, 95, 413
Faison, M.D. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A.R. Taylor, T. L. Landecker, & A.G. Willis, p. 324
Field, G.B., Goldsmith, D.W, & Habing, H.J. 1969, ApJ, 155, L149
Gibson, S.J. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A. R. Taylor, T. L. Landecker, & A. G. Willis, p. 235
Green, D.A. 1993, MNRAS, 262, 328
Hartmann, D. & Burton, W. B. 1997, “Atlas of Galactic Neutral Hydrogen” (Cambridge Univ. Press) (The LD survey)
Hauser, M.G. 2001, “The Extragalactic Infrared Background and its Cosmological Implications”, IAU Symp. 204, ed. M. Harwit & M. G. Hauser, ASP, p. 101
Heiles, C. & Troland, T.H. 2003, ApJ, 586, 1067
Jahoda, K., Lockman, F.J., & McCammon, D. 1990, ApJ, 354, 184
Johnston, S., Koribalski, B., Wilson, W., & Walker, M. 2003, MNRAS, 341, 941
Kalberla, P.M.W., Schwarz, U.J., & Goss, W.M. 1985, A&A, 144, 27
Kappes, M., Kerp, J., & Richter, P. 2003, A&A, 405, 607
Knee, L. B. G. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A.R. Taylor, T.L. Landecker, & A.G. Willis, p. 50
Kulkarni, S.R., & Heiles, C. 1987, in “Interstellar Processes”, ed. D.J. Hollenbach & H. A. Thronson, Jr., Reidel, p. 87
Lazarian, A., & Pogosyan, D. 2000, ApJ, 537, 720
Liszt, H.S. 1983, ApJ, 275, 163
Liszt, H.S. 2001, A&A, 371, 698
Lockman, F.J., Jahoda, K., & McCammon, D. 1986, ApJ, 302, 432
Lockman, F.J. 2002 in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A. R. Taylor, T. L. Landecker, & A. G. Willis, p. 107
McClure-Griffiths, N. M. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A. R. Taylor, T. L. Landecker, & A. G. Willis, p. 58
Minter, A.H., Balser, D.S., & Karlteltepe, J. 2004, ApJ (in press)
Miville-Deschenes, M-A., Boulanger, R, Joncas, G., & Falgarone, E. 2002, A&A, 381, 209
Rachford, B.L., Snow, T.P., Tumlinson, J., Shull, J.M., et al. (2002), ApJ, 577, 221
Reynolds, R.J. 1989, ApJ, 339, L29
Reynolds, R.J., Haffner, L.M., & Tufte, S.L. 1999, in “New Perspectives on the Interstellar Medium”, ASP Conf. Ser. Vol. 168, eds. A. R. Taylor, T. L. Landecker, & G. Joncas, p. 149
Reynolds, R.J., & Tufte, S.L. 1995, ApJ, 439, L17
Richter, P. et al. 2001, ApJ, 559, 318
Stanimirovic, S., Weisberg, J.M., Hedden, A., Devine, K.E., & Green, J.T. 2003, ApJL (in press; astro-ph/0310238)
Taylor, A.R. et al. 2002, in “Seeing Through the Dust”, ASP Conf. Ser. Vol. 276, ed. A. R. Taylor, T. L. Landecker, & A. G. Willis, p. 68
Twain, M. 1883, Life on the Mississippi, James R. Osgood & Co.: Boston
Wakker, B.P., & Boulanger, F. 1986, A&A, 170, 84
Wakker, B.P., & van Woerden, H. 1997, ARAA, 35, 217
Wolfire, M.G., McKee, C.F., Hollenbach, D., & Tielens, A. G. G. M. 2003, ApJ, 587, 278
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2004 Springer Science+Business Media Dordrecht
About this paper
Cite this paper
Lockman, F.J. (2004). Peering Through the Muck: Notes on the Influence of the Galactic Interstellar Medium on Extragalactic Observations. In: Lieu, R., Mittaz, J. (eds) Soft X-Ray Emission from Clusters of Galaxies and Related Phenomena. Astrophysics and Space Science Library, vol 309. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-2564-8_13
Download citation
DOI: https://doi.org/10.1007/978-1-4020-2564-8_13
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-6681-7
Online ISBN: 978-1-4020-2564-8
eBook Packages: Springer Book Archive