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4 Results

The reduced Nançay H I spectra are shown in Fig. 1 for the 19 detected and marginal objects only. Radial velocities, $V_{\rm HI}$, integrated line fluxes, $I_{\rm HI}$, velocity widths at 50% and 20% of peak maximum, W50 and W20, and rms noise levels of our new spectra were measured using standard Nançay reduction software for galaxy observations. The H I profile parameters are listed in Table 1. The upper limits are 3$\sigma$ values for flat-topped profiles with a width of 250 kms-1, a representative value for the W20 width of the detected profiles.

With the Nançay radio telescope, a 100 m-class instrument, 17 out of the 44 galaxies were clearly detected (39% detection rate). In order to get a significantly higher detection rate, observations are required with, e.g., the renovated Nançay telescope (van Driel et al. 1997) (expected to come on-line in September 2000), or with the larger Arecibo telescope. We intend to pursue the acquisition of H I data with these instruments, both as pointed observations and as a blind H I line survey (e.g., Kraan-Korteweg et al. 1998) of the Virgo cluster area.

All galaxies detected in H I have ${M}_{\rm HI}$/LB ratios of $\sim$0.3 - 0.8 ${M}_{\odot}$/ $L_{\odot,B}$, like the average values for Sb-Sm type spirals (Roberts & Haynes 1994). Our results show that the UV flux measured at 2000 Å allows a reliable estimate of the H I line flux of galaxies and hence of their detectability in H I. Of the 6 Coma cluster UV-bright objects (CGCG 097-083, 098-071, 098-078, 160-128, 161-091 and 161-111), 5 were detected in H I. Most of these are classified as spirals, and one as elliptical.

4.1 Notes on individual galaxies

We searched the vicinity of the target objects for nearby spiral galaxies which could potentially give rise to confusion in those Nançay H I profiles where line emission was detected. We used the online NED and LEDA databases, in an area of $5'\,\hspace{-1.7mm}.\hspace{.0mm}5$ $\times$ 30' ( $\alpha\times\Delta$) round the pointing centre, i.e. about 1.5 times the HPBW, as well as optical images extracted from the Digitized Sky Survey.

VCC 31: the galaxy and its surroundings were mapped in H I at Arecibo (Van Zee et al. 1995), and no extended H I emission was found around the object; Arecibo profile parameters are V=2240  kms-1, $I_{\rm HI}=1.53$ Jy kms-1 and W20=132  kms-1. The object was also detected in the present survey.

VCC 234 (= NGC 4241): reported (Magri 1994) as detected in H I at Arecibo (V=2237  kms-1, $I_{\rm HI}=9.0$ Jy  kms-1, W50=359  kms-1), but not detected in the present survey ( $I_{\rm HI}<1.8$ Jy  kms-1) nor at Effelsberg ( $I_{\rm HI}<6.0$ Jy  kms-1, Huchtmeier & Richter 1986b).

VCC 358 (= UGC 7364): detected in H I at Arecibo (Magri 1994); V=2633  kms-1, $I_{\rm HI}=9.0$ Jy  kms-1, but not detected ( $I_{\rm HI}<6.0$ Jy  kms-1) at Effelsberg (Huchtmeier & Richter 1986b). Though our raw spectra show strong baseline curvature due to the proximity of NGC 4261, a large elliptical galaxy with a 21 cm continuum flux density of 19 Jy, such a strong H I profile should have been detected. After fitting a 6th order baseline, our H polarization spectrum has an rms of 11 mJy.

VCC 386 (= NGC 4277): our H I profile appears to be heavily confused by nearby ( $1'\,\hspace{-1.7mm}.\hspace{.0mm}9$ separation) 12.4 mag SBc spiral NGC 4273, which has been observed at Arecibo with a $3'\,\hspace{-1.7mm}.\hspace{.0mm}6$ HPBW, with the following results: V=2386, W50=280  kms-1, W20=298  kms-1 and $I_{\rm HI}=12.8$ Jy  kms-1 (Davis & Seaquist 1983; Helou et al. 1987; Magri 1994; Mirabel & Sanders 1988). Our H I detection appears to be of NGC 4273, given the optical velocities of NGC 4273 (2347 $\pm$ 55  kms-1) and VCC 386 (2504 $\pm$ 51  kms-1) and the Arecibo profile parameters.

VCC 781 (= IC 3303): not detected in 21 cm line synthesis observations at Westerbork (Kotanyi 1981) with an rms noise of 2.5 mJy per synthesized beam, 21 $''\times118$ ( $\alpha\times\delta$).

VCC 951 (= IC 3358): not detected in H I at Green Bank (Fisher & Tully 1981), upper limit 11 Jy kms-1, nor in the present survey ( $I_{\rm HI}$ < 2.2 Jy kms-1).

VCC 1174 (= VIII Zw 187): an optical redshift of 11,840  kms-1 was measured (Gavazzi et al., in prep) for this object after the completion of the present survey. This high redshift is far outside the velocity search ranges of our Nançay observations as well as of the Arecibo observations of Hoffman et al. (see Huchtmeier & Richter 1989).

VCC 1327 (= UGC 7658) and 1348 (= IC 3443): our raw H I profiles, all show that very strong baseline curvature is due to the proximity of M 87, a large elliptical galaxy with a 21 cm continuum flux density of 220 Jy. After fitting a 6th order baseline, the VCC 1327 spectrum has an rms of 6 mJy. The VCC 1348 spectra could not be fitted succesfully even with such a high-order polynomial, and strong ripples (of the order 50 mJy amplitude) remained in the spectra. VCC 1327 was not detected at Effelsberg (Huchtmeier & Richter 1986a), with an rms of 31 mJy.

VCC 1491 (= IC 3486): not detected in H I at Effelsberg by Huchtmeier & Richter (1986a, 1986b), who list the object (erroneously) as IC 3492; upper limit $I_{\rm HI}$ < 8.3 Jy kms-1. The upper limit in the present survey is 2.0 Jy kms-1.

CGCG 098-071: another galaxy was found within the Nançay search area: CGCG 098-73, a $0'\,\hspace{-1.7mm}.\hspace{.0mm}8$ diameter $B_{\rm T}$ 16.0 mag Sbc spiral, $2'\,\hspace{-1.7mm}.\hspace{.0mm}9$ N of the target galaxy at V=6439  kms-1, 400 kms-1 lower than the optical velocity of the target galaxy.

CGCG 098-078 (= Mrk 758): this is the only galaxy classified as elliptical in whose direction H I was detected in our survey, which would imply a high ${M}_{\rm HI}$/LB ratio of 0.7 ${M}_{\odot}$/ $L_{\odot,B}$ if all the gas were to reside in the galaxy. It is not a classical, gas-poor elliptical, though, it is a Markarian type UV-excess object and one of the strongest H$\alpha$ line emitters (EW $_{\rm H\alpha}=82$ Å) in a survey of Coma cluster galaxies (Gavazzi et al. 1998a). The H$\alpha$ emission is almost completely nuclear, and Gavazzi et al. speculated that this may be due to gravitational interaction with a nearby galaxy (see below). The H I profile has a central velocity of 6872 kms-1 and a FWHM of 119  kms-1. The optical redshift of CGCG 98-78 as listed in the LEDA database, 6824 $\pm$ 45  kms-1, is only 47  kms-1 lower than the H I value, and is based on two optical measurements (Denisyuk & Lipovetskii 1983; Lipovetskii & Stepanyan 1986). Another galaxy was found within the Nançay search area, well within the beam: CGCG 098-81, a $1'\,\hspace{-1.7mm}.\hspace{.0mm}1$ diameter $B_{\rm T}$ 15.2 spiral of type Sa [NED]/Sc [LEDA], $1'\,\hspace{-1.7mm}.\hspace{.0mm}4$ N-E of the target galaxy at an optical redshift of 7177 $\pm$ 132 kms-1 (Gavazzi et al. 1999a), i.e., 305  kms-1 higher than the central velocity of our H I profile. In conclusion, the detected H I is quite probably associated with the targeted galaxy, which is not a true elliptical, however.

CGCG 127-18: detected (Gavazzi 1987) in H I at Arecibo (V=2633  kms-1, W20=(162)  kms-1), where poor pointing conditions due to mechanical failure did not allow the measurement of other profile parameters.

CGCG 129-13: the H I velocity is 588 kms-1 lower than the optical. The 6 hours of H I observations were accumulated over 7 days in July and October 1999, and the H I signal is present in all observations, so it appears to be real and not due to radio interference. THe optical velocity is based on a single measurement by Tifft & Gregory (1988), who note that their spectrum is very faint and that consequently no error on the redshift could be given. Our search for nearby galaxies has not shown an object which may cause confusion in the H I data.

CGCG 130-003 (= IC 841): not detected in the CO(1-0) line (Boselli et al. 1995), with a 3$\sigma$ upper limit for a 300  kms-1 broad profile to its H2 mass of 1.0 109 ${M}_{\odot}$ (for D=71.5 Mpc), and not detected in the present H I survey, with an upper limit to its H I mass of 1.6 109 ${M}_{\odot}$.

CGCG 160-128 (= KUG 1301+290): weak detection in the CO(1-0) line (Boselli et al. 1997b), H2 mass of 4 108 ${M}_{\odot}$ (for D=69 Mpc) and a FWHM of 349 kms-1 (no CO line velocity was reported), and detected in the present H I survey, $M_{\rm HI}= 2.6$ 109 ${M}_{\odot}$.

We would like to thank the referee, Dr. M. Roberts, for his comments. We have made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the U.S. National Aeronautics and Space Administration, as well as the Lyon-Meudon Extragalactic Database (LEDA) supplied by the LEDA team at the CRAL-Observatoire de Lyon (France). The Unité Scientifique Nançay of the Observatoire de Paris is associated as Unité de Service et de Recherche USR No. B704 to the French Centre National de Recherche Scientifique (CNRS). Nançay also gratefully acknowledges the financial support of the Région Centre in France.

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