Neutral Hydrogen (HI) in Galaxies


Observations of interstellar neutral hydrogen are based on the 21-cm line. Intensity observations give information about the amount and the distribution of HI; for rotation curves of galaxies based on Doppler observations.

Reviews (methods, results, correlation with other parameters): [Roberts, M.S. in Galaxies and the Universe (Sandage, A., Sandage, M., & warp in the HI distribution at the extreme NE and SW of M31 is reported in Emerson, D.T., Newton, K.in Structure and Properties of Nearby Galaxies (Berkhuijsen, E.M., Wielebinski, R., eds.), Int. Astron. Union Symp. 77, Reidel, Dordrecht (1978). p. 183].

Warps in the HI distribution have been observed in the case of some edge-on spiral galaxies [Sancisi, R. Astron. Astrophys. 53 (1976) 159].

The distribution and the velocity field of HI in 20 bright northern galaxies combined with optical UBV observations is discussed in [van der Kruit, P.C., Searle, L. in Photometry, Kinematics and Dynamics of Galaxies (Evans, D.S., ed.), University of Texas (1979). p. 93].

Interacting Galaxies:

  1. van Moorsel, G., Astron. Astrophys. 202 (1988) 59.
  2. Mirabel, I.F., Dottori, H., & Lutz, D., Astron. Astrophys. 256 (1992) L19.
  3. Hibbard, J.E., Guhathakurta, P., van Gorkom, J.H., & Schweizer, F., Astron. J. 107 (1994) 67.
  4. McNamara, B.R., Sancisi, R., Henning, P.A., & Janar, W., Astron. J. 108 (1994) 844.

Intergalactic HI-Clouds:

  1. Appleton, P.N., Ghio, F.D., van Gorkom, J.H., Schombert, J.M., & Struck-Marcell, C., Nature 330 (1987) 140.
  2. Steidel, C.C., & Sargent, W.L.W., Astrophys. J. 318 (1987) L11.
  3. Schneider, S.E., Astrophys. J. 343 (1989) 84.
  4. Djorgovski, S.., Astron. J. 99 (1990) 31.
  5. McMahon, R.G., Irwin, M.J., Giovanelli, R., Haynes, M.P., Wolfe, & A.M., Hazert, C., Astrophys. J. 359 (1990) 302.
  6. Hoffman, G.L., Salpeter, E.E., Lamphier, C., & Roos, T., Astrophys. J. 388 (1992) L5.
  7. McNamara, B.R., Sancisi, R., Henning, P.A., & Janar, W., Astron. J. 108 (1994) 844.

Galaxies in the Zone of Avoidance:

  1. Kerr, F.J., & Henning, P.A., Astrophys. J. 320 (1987) L99.
  2. Chamaraux, P., Cayatte, V., Balkowski, C., & Fontanelli, P., Astron. Astrophys. 229 (1990) 340.
  3. Lake, G., Schommer, R.A., & van Gorkom, J.H., Astron. J. 99 (1990) 547.
  4. Martin, J.M., Bottinelli, L., Dennefeld, M., Fouque, P., Gouguenheim, L., & Paturel, G., Astron. Astrophys. 235 (1990) 41.
  5. Kraan-Korteweg, R.C., & Huchtmeier, W.K., Astron. Astrophys. 266 (1992) 150.
  6. Capaccioli, M., & Longo, G., Astron. Astrophys. Rev. 4 (1994) 293.
  7. Pantoja, C.A., Giovannardi, C., Altschuler, D.R., & Giovanelli, R., Astron. J. 108 (1994) 921.
  8. Seeberger, R., Huchtmeier, W.K., & Weinberger, R., Astron. Astrophys. 286 286 (1994) 17.
  9. Huchtmeier, W.K., Lercher, G., Seeberger, R., Saurer, W., & Weinberger, R., Astron. Astrophys. 293 (1995) 33.

HI in Voids:

  1. Brosch, N., Astrophys. J. 344 (1989) 597.
  2. Henning, P.A., & Kerr, F.J., Astrophys. J. 347 (1989) L1.

HI in Polar-Ring Galaxies:

  1. Richter, O.G., Sackett, P.D., & Sparke, L.S., Astron. J. 107 (1994) 99.
  2. van Driel, W., Combes, F., Casoli, F., Gerin, M., Nukai, N., Mijayi, T., Hamabe, M., Sofue, Y., Ichikava, T., & Yoshida, S., Astron. J. 109 (1995) 943.

HI in New Nearby Galaxies:

  1. Kraan-Korteweg, R.C., Loan, A.J., Burton, W.B., Lahav, O., Furguson, H.C., Henning, P.A., & Lynden-Bell, D., Nature 372 (1994) 77.
  2. Huchtmeier, W.K., Lercher, G., Seeberger, R., Saurer, W., & Weinberger, R., Astron. Astrophys. 293 (1995) 33.
  3. Krismer, M., Tully, R.B., & Goia, J.M., Astron. J. 110 (1995) 1584.

Many short papers of HI observations are presented in [The Structure and Evolution of normal Galaxies (Fall, S.M., Lynden-Bell, D., eds.), Cambridge Univ. Press (1981)].

In 6 nearby spheroidal dwarf systems no HI was detected. This gives an upper limit of the HI content of dwarf spheroidal galaxies as low as a few parts in 104 by mass [Knapp, G.R., Kerr, F.J., Bowers, P.F. Astron. J. 83 (1978) 360].

The HI mass and the ratio of hydrogen mass to total mass for 140 galaxies are given in [Roberts, M.S. in Galaxies and the Universe (Sandage, A., Sandage, M.; Kristian, J., eds.) = Stars and stellar Systems Vol. IX, Univ. Chicago Press (1975). p. 309].

The distance-independent ratio MHI/L is a function of the morphological type, too, increasing to later type galaxies. The main result is shown in Fig. 8.

Figure 8

Figure 8. The average hydrogen content for different morphological types of galaxies [Li Zong-Yun, & Liu Ru-liang: Acta Astrophys. Sinica 1 (1981) 28; Translation: Chinese Astron. 5 (1981) 205]. (a) Ratio hydrogen mass to total mass, (b) ratio mass to (blue) luminosity. Number of galaxies for each type is indicated. The error bars represent the standard deviation of the sample mean.

Integral properties like mass, luminosity, size, maximal rotation for 169 late-type galaxies determined from H I observations are given in [Shostak, G.S. Astron. Astrophys. 68 (1978) 321].

Compact Groups:

  1. Williams, B.A., & van Gorkom, J.H., Astron. J. 95 (1988) 352.
  2. Rubin, V.C., Hunter, D.A., & Ford Jr., W.K., Astrophys. J. 365 (1990) 86.
  3. Williams, D.R., & Lynch, J.R., Astron. J. 101 (1991) 1969.
  4. Rodrigue, M., Schultz, A., Thompson, J., Colegrove, T., Spight, L.D., Disanti, M., & Fink, U., Astron. J. 109 (1995) 2362.

TULLY-FISHER RELATION:

Tully and Fisher [Tully, R.B., Fisher, J.R. Astron. Astrophys. 54 (1977) 66]. found a relation between the absolute magnitude and the global width of the HI profile for spiral galaxies, i.e. between luminosity and total mass (Fig. 9). This gives a new possibility for distance determination. This relation was studied in the infrared.

  1. Aaronson, M., Huchra, J., Mould, J. Astrophys. J. 229 (1979) 1.
  2. Aaronson, M., Mould, J., Huchra, J. Astrophys. J. 237 (1980) 655.

Figure 9

Figure 9. The Tully-Fisher relation: global width of HI profile DeltaV vs. absolute magnitude for spiral galaxies [Tully, R.B., & Fisher, J.R. Astron. Astrophys. 54 (1977) 661]. DeltaV in [km s-1].

Observational uncertainties (inclination, luminosity correction for internal extinction) and possible systematic effects (differences between morphological types) [Roberts, M.S. Astron. J. 83 (1978) 1026] leave some calibration problems. The slope of the relations lies between -6.25 [Tully, R.B., & Fisher, J.R. Astron. Astrophys. 54 (1977) 661] and -10.0.

  1. Aaronson, M., Huchra, J., & Mould, J. Astrophys. J. 229 (1979) 1.
  2. Aaronson, M., Mould, J., & Huchra, J. Astrophys. J. 237 (1980) 655.

A similar correlation (with absolute magnitudes corrected for total internal absorption) was published by Sandage and Tammann [Sandage, A., & Tammann, G.A. Astrophys. J. 210 (1976) 7, (Fig. 1)].

The so-called Tully-Fisher-relation is an empirical dependence between the luminosity and the dynamical mass (i.e. the maximum rotational velocity) of galaxies. The observed magnitude has to be corrected for extinction in our galaxy (depending on galactic latitude to the first order) and for intrinsic absorption within the observed galaxy (depending on the inclination and the morphological type of the galaxy). The indices 0 and i indicate that these corrections have been applied. The correlation between corrected absolute magnitude M0,iB,T and the corrected full line width of the integrated neutral hydrogen profile dv0,i - the Tully-Fisher relation:

M0,iB,T propto log d v0,i ,

has been used as a tool for determining extragalactic distances

  1. Bottinelli, L., Fouque, P., Gouguenheim, L., Teerikorpi, P., & Paturel, G., Astron. Astrophys. 181 (1987) 1.
  2. Tacconi, L.J., & Young, J.S., Astrophys. J. 322 (1987) 681.
  3. Kraan-Korteweg, R.C., Cameron, L.M., & Tammann, G.A., Astrophys. J. 331 (1988) 620.
  4. Baan, W.A., Haschick, A.D., & Henkel, C., Astrophys. J. 346 (1989) 680.
  5. Mould, J., Han, M., & Bothun, G., Astrophys. J. 347 (1989) 112.
  6. Biviano, A., Giuricin, G., Mardirossian, F., & Mezzetti, M., Astrophys. J. Suppl. 74 (1990) 325.
  7. Fouque, P., Bottinelli, L., Durand, N., Gouguenheim, L., & Paturel, G., Astron. Astrophys. Suppl. 86 (1990) 473.
  8. Fouque, P., Bottinelli, L., Gouguenheim, L., & Paturel, G., Astrophys. J. 349 (1990) 1.
  9. Freedman, W.L., Astrophys. J. 355 (1990) 35.
  10. Puche, D., Carignan, C., & Bosma, A., Astron. J. 100 (1990) 1468.
  11. Teerikorpi, P., Astron. Astrophys. 234 (1990) 1.
  12. Fabian, A.C., Nulsen, P.E.J., & Canizares, C.R., Astron. Astrophys. Rev. 2 (1991) 191.
  13. Fukugita, M., Okamura, S., Tarusawa, K., & Rood, H.J., Astrophys. J. 376 (1991) 8.
  14. Haynes, M.P., & Giovanelli, R., Astrophys. J. Suppl. 77 (1991) 331.
  15. Karachentsev, I.D., Astron. Letters 17 (1991) 176.
  16. Persic, M., & Salucci, P., Mon. Not. R. Astron. Soc. 248 (1991) 325.
  17. Peletier, R.F., & Willner, S.P., Astrophys. J. 382 (1991) 382.
  18. Baan, W.A., Rhoads, J., & Haschick, A.D., Astrophys. J. 401 (1992) 508.
  19. Bicknell, G.V., Astrophys. J. 399 (1992) 1.
  20. Teerikorpi, P., Bottinelli, L., Gouguenheim, L., & Paturel, G., Astron. Astrophys. 260 (1992) 17.
  21. Fukugita, M., Okamura, S., & Yasuda, N., Astrophys. J. 412 (1993) L13.
  22. Guhathakurta, P., Bernstein, G., Raychaudhury, S., Haynes, M.P., Giovanelli, R. Herter, I., & Vogt, N., Pub. Astron. Soc. Pac. 105 (1993) 1022.
  23. Peletier, R.F., & Willner, S.P., Astrophys. J. 418 (1993) 626.
  24. Rood, H.J., & Williams, B.A., Mon. Not. R. Astron. Soc. 263 (1993) 211.
  25. Teerikorpi, P., Astron. Astrophys. 280 (1993) 443.
  26. Bernstein, G.M., Guhathakurta, P., Raychaudhury, S., Giovanelli, R., Haynes, M.P., Heter, T., & Vogt, N.P., Astron. J. 107 (1994) 1962.
  27. Feast, M.W., Mon. Not. R. Astron. Soc. 266 (1994) 255.
  28. Federspiel, M., Sandage, A., & Tammann, G.A., Astrophys. J. 430 (1994) 29.
  29. Rownd, B.K., Dickey, J.M., & Helou, G., Astron. J. 108 (1994) 1638.
  30. Di Nella, H., Garcia, A.M., Garnier, R., & Paturel, G., Astron. Astrophys. Suppl. 113 (1995) 151.
  31. Sandage, A., Tammann, G.A., & Federspiel, M., Astrophys. J. 452 (1995) 1.
  32. Sprayberry, D., Bernstein, G.M., Impey, C.D., & Bothun, C.D., Astrophys. J. 438 (1995) 72.
  33. van Driel, W., van den Broek, A.C., & Baan, W.A., Astrophys. J. 444 (1995) 80.

Calibration and Corrections for Malmquist Bias:

  1. Weinberg, D.H., Szomora, A., Guhathakurta, P., & van Gorkom, J.H., Astrophys. J. 372 (1991) L13.
  2. Taylor, C., Brinks, E., & Skillman, E.D., Astron. J. 105 (1993) 128.
  3. Pantoja, C.A., Giovannardi, C., Altschuler, D.R., & Giovanelli, R., Astron. J. 108 (1994) 921.

and Galaxy Shape:

  1. Freedman, W.L., Astrophys. J. 355 (1990) 35.
  2. Fasano, G., & Bettoni, D., Astron. J. 107 (1994) 1649.
  3. Sandage, A., Tammann, G.A., & Federspiel, M., Astrophys. J. 452 (1995) 1.

Using CO Linewidths:

  1. Dickey, J.M., & Kazes, I., Astrophys. J. 393 (1992) 530.
  2. Sofue, Y., Pub. Astron. Soc. Japan. 44 (1992) 231.
  3. Schoniger, F., & Sofue, Y., Astro. Astrophys. 283 (1994) 21.

for Dwarf Galaxies: [Pantoja, C.A., Giovannardi, C., Altschuler, D.R., & Giovanelli, R., Astron. J. 108 (1994) 921].

The lower absorption in the IR reduces the scatter of the (blue) TF relation:

  1. Fouque, P., Bottinelli, L., Durand, N., Gouguenheim, L., & Paturel, G., Astron. Astrophys. Suppl. 86 (1990) 473.
  2. Peletier, R.F., & Willner, S.P., Astrophys. J. 382 (1991) 382.
  3. Garcia, A.M., Bottinelli, L., Garnier, R., Gouguenheim, L., & Paturel, G., Astron. Astrophys. Suppl. 97 (1993) 801.
  4. Peletier, R.F., & Willner, S.P., Astrophys. J. 418 (1993) 626.
  5. Bernstein, G.M., Guhathakurta, P., Raychaudhury, S., Giovanelli, R., Haynes, M.P., Heter, T., & Vogt, N.P., Astron. J. 107 (1994) 1962.
  6. Schulman, E., Bregman, J.N., & Roberts, M.S., Astrophys. J. 423 (1994) 180.

The most optimistic estimate for the accuracy of distances derived from the IR TF relation is 5% [Baas, F., Israel, F.P., & Koorneef, J., Astron. Astrophys. 284 (1994) 403]. for the calibrator galaxies.

Figure 1

Figure 1. The relative neutral hydrogen content as a function of morphological type. The distance-independent quantity MHI/LB is often used as the relative HI content to be compared with other global galaxian parameters. Here we compare the dependence of MHI/LB with morphological type for two galaxy samples. The averages per morphological type are given for the:

1) sample of nearby galaxies (v0 leq 500 km s-1), data from [Huchtmeier, W.K., & Richter, O.-G., Astron. Astrophys. 203 (1988) 237] are shown as open squares,

2) sample of galaxies from [Roberts, M.S., & Haynes, M.P., Annu. Rev. Astron. Astrophys. 32 (1994) 115] are given as filled circles.

3) sample of Sa galaxies [Huchtmeier, W.K., (1995) in preparation] from the RSA [A revised Shapeley-Ames Catalog of Bright Galaxies (Sandage, A.R., Tammann, G.A.), Washington D.C., Carnegie Institution (1987)] are shown as open circles for the morphological subtypes as defined by Sandage [Hogg, D.E., Roberts, M.S., & Sandage, A.R., Astron. J. 106 (1993) 907].

The general trend of MHI/LB to increase with morphological type seems to be valid even for the Sa subtypes. However, the MHI/LB for the earliest subtype is very low as most Sa galaxies of this subtype are HI-deficient objects in the Virgo cluster and in nearby groups. The filled square represents the mean MHI/LB value for Sa galaxies outside the Virgo cluster, the filled upper triangle the mean for Sa galaxies within the Virgo cluster, and the filled lower triangle the mean for the Sa galaxies in the Coma I cloud [Garcia-Barreto, J.A., Downes, D., & Huchtmeier, W.K., Astron. Astrophys. 288 (1994) 705]. The broken line represents the whole data set of "normal" galaxies and will be used in the following figures for comparison with different galaxy samples.

Figure 2

Figure 2. HI-deficiency in selected groups of galaxies. MHI/LB versus morphological type is given for a selected sample of seven galaxy groups (from [Nearby Galaxies Catalog (Tully, R.B.), Cambridge, Cambridge University Press (1988)]) [Huchtmeier, W.K., & Garcia-Barreto, J.A., (1995) unpublished data] with early-type galaxies in their central areas. Galaxy group, 21-1 (triangle down), 41-1 (square on top), 42-1 (triangle up), 42-13 (square), 51-4+4 (star), 52-7+7 (circle). Coma I group (x), upper limits are indicated by arrows. The full line represents the sample of nearby galaxies (see Fig. 1), the two broken lines mark the 95% confidence interval. Most disk galaxies from these selected groups fit nicely to the relation defined by the sample of nearby galaxies. However, a small number of early-type disk galaxies is definitely HI-deficient (up to two orders of magnitude for the Sa galaxy NGC 4314 in the Coma I group). The HI detected elliptical galaxies show very low values of MHI/LB (compared to the thick broken line, an extrapolation of the HI-rich part of the relation for nearby galaxies).

Figure 3

Figure 3. HI-deficiency in the Virgo cluster. The relative HI content MHI/LB is plotted versus blue luminosity. The nearby galaxy sample (filled circles, [Huchtmeier, W.K., & Richter, O.-G., Astron. Astrophys. 203 (1988) 237]) is fitted by the full line. Virgo galaxies (open circles, [Huchtmeier, W.K., & Richter, O.G., Astron. Astrophys. 210 (1989) 1]) partly fall in the range of the diagram occupied by the nearby galaxy sample. A considerable number of Virgo galaxies has MHI/LB values much lower than expected for their luminosity. This is the manifestation of the HI deficiency observed in several clusters and in a few nearby groups (see Fig. 2). Other manifestations of the HI deficiency are found in plots of MHI/LB against a number of different global parameters like morphological type, total mass, linear extent. Open squares indicate bright galaxies from the Hydra cluster [Huchtmeier, W.K., in [The Evolution of Galaxies and their Environment. Proceedings of the Third Teton Summer School of Astrophysics (D. Hollenbach, H.A. Thronson, & J.M. Shull, eds.), Washington, NASA Conference Publication 3190 (1993) p. 207].

Figure 4

Figure 4. The relative HI-content of elliptical galaxies. MHI/LB versus LB is given for two complete samples of elliptical galaxies [Huchtmeier, W.K., Sage, L.J., & Henkel, C., Astron. Astrophys. 300 (1995) 675] :

a) elliptical galaxies from the RSA [A Revised Shapeley-Ames Catalog of Bright Galaxies (Sandage, A.R, & Tammann, G.A.), Washington D.C., Carnegie Institution (1987)], filled triangles,

b) elliptical galaxies with IRAS 100 ยตm fluxes geq 0.5 Jy [Knapp, G.R., Guhathakurta, P., Kim, D.-W., & Jura, M., Astrophys. J. Suppl. 70 (1989) 329], filled circles.

Upper limits for both samples are given by open circles. The full line represents the nearby galaxy sample [Huchtmeier, W.K., & Richter, O.-G., Astron. Astrophys. 203 (1988) 237], see Fig. 3. The great number of upper limits is partially due to lack of sensitivity. In general elliptical galaxies are poor in HI, low upper limits and detection are as low as three orders of magnitude below the expected values (full line) for disk galaxies. However, a few elliptical galaxies have MHI/LB values as high as spiral galaxies. These objects are in some way peculiar and tend to have blue colors (indicated by greater filled circles).

Figure 5

Figure 5. The "blue" Tully-Fisher relation - logarithm of the corrected total blue absolute magnitude M0,iB,T versus logarithm of the corrected HI-linewidth dv0,i - for the sample of nearby galaxies (filled circles [Huchtmeier, W.K., & Richter, O.-G., Astron. Astrophys. 203 (1988) 237]), the Virgo cluster sample (open circles [Huchtmeier, W.K., & Richter, O.G., Astron. Astrophys. 210 (1989) 1]), and the Hydra cluster (open squares). Dwarf galaxies show a greater scatter due to uncertainties of their inclination values. Cluster galaxies show a higher scatter due to the greater observational errors (greater distances).

Observations of HI in Cluster Galaxies:

HI in the Virgo cluster:

  1. Hoffman, G.L., Helou, G., Salpeter, E.E., & Sandage, A.R., Astrophys. J. 289 (1985) L15.
  2. Huchtmeier, W.K., & Richter, O.-G., Astron. Astrophys. Suppl. 64 (1986) 111.
  3. Hoffman, G.L., Helou, G., Salpeter, E.E., Glossun, J., & Sandage, A.R., Astrophys. J. Suppl. 63 (1987) 247.
  4. Skillman, E.D., Bothun, G.D., Murray, M.A., & Warmels, R.H., Astron. Astrophys. 185 (1987) 61.
  5. Guhathakurta, P., van Gorkom, J.H., & Kotany, C., Astron. J. 96 (1988) 851.
  6. Phillips, S., Astron. Astrophys. 194 (1988) 77.
  7. van Driel, W., Rots, A.H., & van Woerden, H., Astron. Astrophys. 204 (1988) 39.
  8. Warmels, R.H., Astron. Astrophys. Suppl. 72 (1988) 19.
  9. Warmels, R.H., Astron. Astrophys. Suppl. 72 (1988) 57.
  10. Warmels, R.H., Astron. Astrophys. Suppl. 72 (1988) 427.
  11. Warmels, R.H., Astron. Astrophys. Suppl. 73 (1988) 453.
  12. Hoffman, G.L., Helou, G., Salpeter, E.E., & Lewis, B.M., Astrophys. J. 339 (1989) 812.
  13. Hoffman, G.L., Williams, B.M., Lewis, B.M., Helou, G., & Salpeter, E.E., Astrophys. J. Suppl. 69 (1989) 65.
  14. Hoffman, G.L., Williams, H.L., Salpeter, E.E., Sandage, A.R., & Binggeli, B., Astrophys. L. Suppl. 71 (1989) 701.
  15. Huchtmeier, W.K., & Richter, O.G., Astron. Astrophys. 210 (1989) 1.
  16. Cayatte, V., van Gorkom, J.H., Balkowski, C., & Kotanyi C., Astron. J. 100 (1990) 604.
  17. Schneider, S.E., Thuan, T.X., Magri, C., & Wadiak, J.E., Astrophys. J. Suppl. 72 (1990) 245.
  18. Cayatte, V., Kotany, C., Balkowski, C., & van Gorkom, J.H., Astron. J. 107 (1994) 1003.
  19. Boselli, A., Astron. Astrophys. 292 (1994) 1.

HI in the Hydra-Centaurus cluster:

  1. Richter, O.-G., & Huchtmeier, W.K., Astron. Astrophys. Suppl. 68 (1987) 427.
  2. Aaronson, M., Bothun, G.D., Cornell, M.E., Dawe, J.A., Dickens, J.R., Hall, P.J., Sheng, H.M., Huchra, J.P., Lucey, J.R., Mould, J.R., Murray, J.D., Schommer, R.A., & Wright, A.., Astrophys. J. 338 (1989) 654.
  3. McMahon, P.M., Richter, O.-G., van Gorkum, J.H., & Ferguson, H.C., Astron. J. 103 (1992) 399.

HI in the Coma cluster:

  1. Gavazzi, G., Astrophys. J. 320 (1987) 96.
  2. Gavazzi, G., Astrophys. J. 346 (1989) 59.
  3. Casoli, F., Boisse, P., Combes, F., & Dupraz, C., Astron. Astrophys. 249 (1991) 359.
  4. Dickey, J.M., & Gavazzi, G., Astrophys. J. 373 (1991) 347.

HI in the Perseus-Pisces cluster:

  1. Focardi, P., Marano, B., & Vettolani, G., Astron. Astrophys. 136 (1984) 178.
  2. Hauschildt, M., Astron. Astrophys. 184 (1987) 43.
  3. Chamaraux, P., Cayatte, V., Balkowski, C., & Fontanelli, P., Astron. Astrophys. 229 (1990) 340.
  4. Giovanelli, R., & Haynes, M.P., Astron. J. 97 (1989) 633.
  5. Chamaraux, P., Cayatte, V., Balkowski, C., & Fontanelli, P., Astron. Astrophys. 229 (1990) 340.
  6. Seeberger, R., Huchtmeier, W.K., & Weinberger, R., Astron. Astrophys. 286 286 (1994) 17.

HI in the Hercules cluster:

  1. Freudling, W., Haynes, M.P., & Giovanelli, R., Publ. Astron. Soc. Pacific 190 (1988) 1220.
  2. Freudling, W., Haynes, M.P., & Giovanelli, R., Astron. J. 96 (1988) 1791.
  3. Freudling, W., Astron. Astrophys. Suppl. 112 (1995) 429.

HI in the Fornax cluster:

  1. D'Onofrio, M., Zaggia, S.A., Longo, G., Caou, N., & Capaccioli, M., Astron. Astrophys. 296 (1995) 319.
  2. Horellou, C., Casoli, F., Dupras, C., Astron. Astrophys. 303 (1995) 361.

HI in Galaxy Clusters:

  1. Magri, C., Haynes, M.P., Forman, W., Jones, C., & Giovanelli, R., Astrophys. J. 333 (1988) 136.
  2. Haynes, M.P., & Giovanelli, R., Astrophys. J. Suppl. 77 (1991) 331.
  3. Hoffman, G.L., & Williams, H.L., Astron. J. 101 (1991) 325.
  4. Richter, O.-G., & Huchtmeier, W.K., Astron. Astrophys. Suppl. 87 (1991) 425.
  5. Williams, B.A., McMahon, P.M., & van Gorkom, J.H., Astron. J. 101 (1991) 1957.
  6. Scodeggio, M., Boselli, A., Gavazzi, G., Trinchieri, G., & Carilli, B., Astron. Astrophys. Suppl. 94 (1992) 299.
  7. Hogg, D.E., Roberts, M.S., & Sandage, A.R., Astron. J. 106 (1993) 907.
  8. Scodeggio, M., & Gavazzi, G., Astrophys. J. 409 (1993) 110.
  9. Vallee, J.P., Astrophys. Space Sci. 206 (1993) 275.
  10. Dwarakanath, K.S., van Gorkom, J.H., & Owen, F.N., Astrophys. J. 432 (1994) 469.
  11. O'Dea, C.P., Baum, S.A., & Gallimore, J.E., Astrophys. J. 436 (1994) 669.
  12. Giovanelli, R., Scodeggio, M., Solanes, J.M., Haynes, M.P., Arce, H., & Skai, S., Astron. J. 109 (1995) 1451.
  13. Mould, J., Martin, S., Bothun, G., Huchra, J., & Schommer, B., Astrophys. J. Suppl. 96 (1995) 1.

HI in Cooling Flows:

  1. McNamara, B.B., Bregman, J.N., & O'Connell, R.W., Astrophys. J. 360 (1990) 20.
  2. Dwarakanath, K.S., van Gorkom, J.H., & Owen, F.N., Astrophys. J. 432 (1994) 469.

HI-Absorption in Galaxies:

  1. Brown, R.L., Broderick, J.J., Johnston, K.J., Benson, J.M., Mitchell, K.J., & Waltmman, M.B., Astrophys. J. 329 (1988) 138.
  2. Dickey, J.M., & Brinks, E., Mon. Not. R. Astron. Soc. 233 (1988) 781.
  3. Krishan, V., Mon. Not. R. Astron. Soc. 231 (1988) 353.
  4. van Gorkom, J.H., Knapp, G.R., Ekers, R.D., Ekers, D.D., & Laing, R.A., Astron. J. 97 (1989) 708.
  5. Baan, W.A., Rhoads, J., & Haschick, A.D., Astrophys. J. 401 (1992) 508.
  6. Carilli, C.L., Perlman, E.S., & Stocke, J.T., Astrophys. J. 400 (1992) 13.
  7. Dickey, J.M., Brinks, E., & Puche, D., Astrophys. J. 385 (1992) 501.
  8. Dickey, J.M., & Brinks, E., Astrophys. J. 405 (1993) 153.
  9. Schneider, S.E., & Corbelli, E., Astrophys. J. 414 (1993) 500.
  10. Gallimore, J.F., Baum, S.A., O'Dea, C.P., Brinks, E., & Pedlar, A., Astrophys. J. 422 (1994) 13.
  11. O'Dea, C.P., Baum, S.A., & Gallimore, J.E., Astrophys. J. 436 (1994) 669.
  12. Schiminovich, D., van Gorkom, J.H., van der Hulst, J.M., & Kasow, S., Astrophys. J. 423 (1994) L101.
  13. Taramopoulos, A., Briggs, F.H., & Turnshek, D.A., Astron. J. 107 (1994) 193.
  14. Conway, J.E., & Blanco, P.R., Astrophys. J. 449 (1995) 131.
  15. Dwarakanath, K.S., Owen, F.N., & van Gorkom, J.H., Astrophys. J. 442 (1995) L1.
  16. Taylor, C.L., Brinks, E., Grushuis, R.M., & Skillman, E.D., Astrophys. J. Suppl. 99 (1995) 427.

HI in Radio Galaxies:

  1. van Gorkom, J.H., Knapp, G.R., Ekers, R.D., Ekers, D.D., & Laing, R.A., Astron. J. 97 (1989) 708.
  2. England, M.N., & Gottesman, S.T., Astron. J. 100 (1990) 96.
  3. Jaffe, W., Astron. Astrophys. 240 (1990) 254.
  4. Mirabel, I.F., Astrophys. J. 352 (1990) L3.
  5. van Gorkom, J.H., van der Hulst, J.M., Haschick, A.D., & Tubbs, A.D., Astron. J. 99 (1990) 1781.
  6. Ikeuchi, S., Astron. Space Res. 11 (1991) 245.
  7. Carilli, C.L., & van Gorkom, J.H., Astrophys. J., 399 (1992) 372.
  8. Wieringa, M.H., de Bruyn, A.G., & Katgert, P., Astron. Astrophys. 256 (1992) 331.
  9. Schneider, S.E., & Corbelli, E., Astrophys. J. 414 (1993) 500.
  10. Dwarakanath, K.S., Owen, F.N., & van Gorkom, J.H., Astrophys. J. 442 (1995) L1.

General:

  1. Broeils, A.H., Astron. Astrophys. 256 (1992) 19.
  2. Elmegreen, B.G., Astrophys. J. 411 (1993) 170.
  3. Maia, M.A.G., Da Costa, L.N., Giovanelli, R., & Haynes, M.P., Astron. J. 105 (1993) 2107.
  4. Rao, S., & Briggs, F., Astrophys. J. 419 (1993) 515.
  5. Vallee, J.P., Astrophys. Space Sci. 206 (1993) 275.
  6. Golla, G., & Hummel, E., Astron. Astrophys. 284 (1994) 777.
  7. Taramopoulos, A., Briggs, F.H., & Turnshek, D.A., Astron. J. 107 (1994) 193.
  8. Braun, R., Astron. Astrophys. Suppl. 114 (1995) 409.
  9. Corbelli, E., & Salpeter, E.E., Astrophys. J. 450 (1995) 32.
  10. Helfer, T.I., & Blitz, L., Astrophys. J. 450 (1995) 90.
  11. Sofue, Y., Honma, M., & Arimoto, N., Astron. Astrophys. 296 (1995) 33.


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