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New Galaxies Discovered in the First Blind HI Survey of the Centaurus A Group

We have commenced a 21-cm survey of the entire southern sky (\delta<0 degrees, -1200 km/s<v<12700 km/s) which is ''blind'', i.e. unbiased by previous optical information. In the present paper we report on the results of a pilot project which is based on data from this all-sky survey. The project was carried out on an area of 600 square degrees centred on the nearby Centaurus A (Cen A) group of galaxies at a mean velocity of v ~ 500 km/s. This was recently the subject of a separate and thorough optical survey. We found 10 new group members to add to the 21 galaxies already known in the Cen A group: five of these are previously uncatalogued galaxies, while five were previously catalogued but not known to be associated with the group. We found optical counterparts for all the HI detections, most of them intrinsically very faint low surface brightness dwarfs. The new group members add approximately 6% to the HI mass of the group and 4% to its light. The HI mass function, derived from all the known group galaxies in the interval 10^7 \Msun of HI to 10^9 \Msun of HI, has a faint-end slope of 1.30 +/- 0.15, allowing us to rule out a slope of 1.7 at 95% confidence. Even if the number in the lowest mass bin is increased by 50%, the slope only increases to 1.45 +/- 0.15.


Introduction
Recent developments in technology make it possible to perform for the first time large-area sensitive blind surveys at 21-cm to search for extragalactic Hi. This opens many scientific opportunities. Most importantly, the selection effects through the 21-cm window will be quite different from the well known optical selection effects which may presently bias our understanding of galaxy populations (e.g. Impey & Bothun 1997, Disney 1998. For instance, low surface brightness (LSB) galaxies are dimmer than the sky and nearby gas-rich dwarf galaxies show a morphology confusingly similar to background giant galaxies which make both galaxy types very difficult to identify optically. But they may well become "visible" in a 21-cm survey if they have a significant amount of Hi. LSB galaxies appear to be common -with approximately equal numbers of galaxies, of a given size, in each one-magnitude bin of blue central surface brightness µ B,0 measured between 21.5 < µ B,0 < 26.5 (Turner et al. 1993;McGaugh 1996). Considering the relative narrowness of the bins at fainter magnitudes this is a remarkable result. The cosmological significance of LSB galaxies remains controversial because of uncertain optical selection effects at faint luminosities (see Impey & Bothun 1997, Disney 1998 and references therein).
Likewise there is serious disagreement about the relative number of faint dwarf galaxies. Magnitude-limited surveys tend to find a flat faint-end slope (Schechter, 1976, parameter α ∼ 1) to the optical luminosity function (e.g. Loveday et al. 1992, Lin et al. 1996. This would suggest that the total light contribution from dwarfs in the universe is insignificant, whereas surveys within clusters of galaxies (e.g. de Propris et al. 1995;Driver & Phillipps 1996;Trentham 1997;Phillipps, Parker, Schwartzenberg & Jones 1998) find steep faint end slopes with α > 2, suggesting a dominant role for dwarfs in the determination of the light content of the universe.
Dwarf galaxies may also contain appreciable amounts of dark matter (e.g. Freeman 1997), implying that they may add even more to the overall mass in the universe than to the light. Finally, any extragalactic survey in which every object is automatically tagged with its velocity-distance offers rare opportunities for statistical studies.
Blind 21-cm surveys have a long history but their ambitions have been severely curtailed by technological limitations. Single dish radio telescopes large enough to reach high sensitivity have had beam areas too small to survey large areas of sky, while interferometric surveys are still confined to relatively narrow velocity windows by the computer power required to carry out the necessary cross-correlations between every interferometer pair.
Nevertheless, in recent times blind surveys have been carried out in the galaxy clusters Hydra by McMahon et al. (1993) and Hercules by Dickey (1997); in voids by Krumm & Bosch (1984) and Weinberg et al. (1991); behind the Galactic plane by Kerr & Henning (1987); and in the field by Henning (1995). Latterly, narrow zenith-strip scans have been done at Arecibo (see later) by Spitzak & Schneider (1998) and Zwaan et al. (1997).
The most recent 21-cm survey is our Hi Parkes All-Sky Survey (HiPASS ) which started early in 1997 and is expected to be complete within ∼3 years. This project takes advantage of the new multibeam instrument at the 64m radio telescope at Parkes (Australia) equipped with 13 separate beams (26 receivers) and enough correlator power in each beam to survey 1024 velocity channels simultaneously. The scientific aims of the project include a study of the Galactic Hi and of the galaxy content of the local universe. For this purpose we scan the complete southern sky in the velocity range −1200 km s −1 < v ⊙ < 12, 700 km s −1 .
For the purpose of testing the performance of HiPASS the present limited study was carried out using the first set of HiPASS data completed to full sensitivity. The selected area covers a substantial fraction of the nearby Centaurus A group of galaxies. The main reasons for this choice are twofold: (1) the Cen A group is among the closest galaxy groups to the Local Group at ∼ 3.5 Mpc (Hui et al. 1993;Sandage et al. 1994) and contains the richest population of different morphological galaxy types (de Vaucouleurs 1979), including the peculiar giant elliptical NGC 5128, the large disk galaxies M 83 and NGC 4945, the S0 galaxy NGC 5102, and the active star forming galaxy NGC 5253. All main group members appear disturbed in their morphology.
It has been suggested (Graham 1979;van Gorkom et al. 1990) that the recent accretion of a population of gas-rich dwarfs could be the reason. The group lies in the Supergalactic Plane with its southern extension running down to low galactic latitudes making optical studies challenging because of high extinction. (2) The group has recently been the subject of a careful optical survey (Côté et al. 1997) enabling comparison between contemporary optical searches for gas-rich type (irregular) galaxies and our "blind" Hi survey.
Most earlier Hi studies of groups of galaxies have been done based on previous optical identifications of candidate members. In the M 81 group, van Driel et al. (1998) and Huchtmeier & Skillman (1998) have independently done 21 cm searches for optically selected dwarf candidates. Neither group detected any new members. Huchtmeier, Karachentsev & Karachentseva (1997) followed up on potential dwarfs found on the Second Palomar Sky Survey (POSS II), and found 1 new candidate of the IC 342/Maffei group, and three new dwarf members each in the NGC 6946 and NGC 672/IC 1727 groups. Maia & Willmer (1998) have studied the neutral hydrogen content of a number of "loose groups", but they also used pointed observations of optical candidates.
Several Hi searches of compact groups of galaxies have been done (Oosterloo & Iovino 1997;Williams & van Gorkom 1997;Williams, McMahon & van Gorkom 1991), however these groups are usually far enough away that both the spatial resolution and the sensitivity preclude detecting dwarf galaxies. However, a few nearby groups have been surveyed blind at 21 cm, and they include M 81, CVnI and NGC 1023, in which Lo & Sargent (1979) found 4 previously uncatalogued members, and a part of the Sculptor group, studied by Haynes & Roberts (1979) who found uncatalogued Hi objects thought to be group members.
The present paper is organised as follows: §2 describes the 21-cm survey; the observations with results are given in §3 and §4. The optical follow-up on the newly detected galaxies and their optical properties are presented in §5 and §6. In §7 we derive the Hi Mass Function for the Cen A group. Finally, we discuss detection limits and future projects in §8.

Survey
The Cen A group covers approximately 1000 square degrees of sky down to and perhaps through the galactic plane. Since it is also projected against the Supergalactic plane, the area is rich in galaxies and therefore well suited to test the performance of HiPASS .
The comparison optical search for dwarf irregulars in the area by Côté et al. (1997; hereafter C97) covered 900 square degrees between 12 h 30 m < α < 15 h 00 m and −50 • < δ < −20 • whereas we have surveyed a smaller area of 600 square degrees, chosen because it fits into the HiPASS survey grid. C97 found 18 Hi rich dIrr's (2 new) of which 14 were in our search-area. Adding AM 1321-304 found by Matthews & Gallagher (1996) and the six well known bright group members NGC 5128, M 83, NGC 4945, NGC 5102, NGC 5253 and ESO 270-G017 means there were in all 21 suspected group members in our 600 square degree search area prior to our survey, with another 7 outside (see Figure 1). Our search was confined to the velocity range 200 < v ⊙ < 1000 km s −1 , cut off at the lower end because of the possibility of confusion with High Velocity Clouds which are numerous in the Cen A group direction (Wakker, 1991). One group member -CEN 5 (v ⊙ =160 km s −1 ) with a velocity lower than 200 km s −1 has been previously claimed (C97) and there remains the possibility that other group members in our data remain excluded by the 200 km s −1 restriction.
If we exclude CEN 5 from the statistics then there were in our search area, prior to this survey, 18 suspected group members with Hi detections and two with Hα (NGC 5206 and ESO 272-G025).

Observations and Data Reduction
The 21-cm observations for this pilot study were carried out in February and March 1997 as part of the HiPASS survey which is ongoing at the 64m single dish Parkes Radio Telescope. This data set comprises the first completed area observed to full sensitivity with HiPASS . The instrument is a multibeam system consisting of 13 beams, each with 2 orthogonal polarisations. The scanning rate across the sky is 1 degree/minute at constant right ascension. The data from the 26 correlators are stored every 5 seconds. Each correlator has 1024 channels tuned to a velocity range between −1200 km s −1 to 12, 700 km s −1 , corresponding to a channel separation of 13.2 km s −1 . The system temperature, T sys , is ∼ 21 K and the scanning pattern is organised so that every point in the sky passes through several beams during a scan, and through several different scans separated by days or weeks of time depending on the observing schedule. This allows for the rejection of time-dependent interference. The total integration time per point on the sky is 450 seconds. The 5σ sensitivity of the HiPASS survey is measured at 70 mJy per channel per beam. For more details about the multibeam system we refer to Staveley-Smith et al. (1996). The observed spectra were smoothed on-line by applying a 25% Tukey filter, to reduce "ringing" caused by the strong Galactic signal entering through spectral side lobes.
This process accounts for a loss in velocity resolution of 37%. Consequently the actual velocity resolution is 18.2 km s −1 , or 35 km s −1 after Hanning smoothing. A description of the on-line data reduction at the telescope which involves bandpass correction can be found in Barnes et al. (1998). Three-dimensional data cubes (α, δ, v ⊙ ) were produced by putting individual spectra onto a pixel grid of 4 ′ × 4 ′ . Due to the lack of an automatic source finder at this early stage of the HiPASS survey, these cubes were visually searched for Hi sources by moving through the velocity range 0 < v ⊙ < 1000 km s −1 , which covers the velocity distribution of the Cen A group, and corresponds to 1000 km s −1 /35 km s −1 =28 independent velocity resolution elements at a given spatial pixel on the sky. Given that there are 10,000 such pixels in this survey, we searched through 280,000 independent "cubicles" (i.e. 3-dimensional pixels).
The 1σ sensitivity of the HiPASS survey was measured at 14 mJy/channel. Assuming noise normally distributed about zero, we expect statistically to find ∼ 0.1 spurious positive 5-sigma detections in the data.
However, 27 objects with velocities v ⊙ > 200 km s −1 were found at this detection threshold (plus CEN 5).
Among others we recovered main Cen A group members such as NGC 4945, NGC 5102, M 83, NGC 5237, and NGC 5253. NGC 5128 remained undetected because the Hi emission was swamped by strong continuum emission from that galaxy.
Many more Hi sources have been identified with velocities v ⊙ < 200 km s −1 . These are most likely not galaxies but galactic high velocity clouds, as there is a clear overlap in velocity space between nearby galaxies and the system of HVCs of our Galaxy towards the Cen A group direction (Wakker 1991). Because of the number dominance of high velocity clouds, and because only one Cen A group galaxy is known below 200 km s −1 to date (CEN 5, see Table 1), we restricted our study and optical follow-up program (see §5) to detections with v ⊙ > 200 km s −1 .

Hi properties
We determined the Hi fluxes of our detections by making zero-th moment maps. A MIRIAD (Sault et al. 1995) gauss fitting routine yielded an estimate of the object's coordinates (α, δ) (cols.
[2] and [3] in Table   1). Positional accuracy should equal the half-power beamwidth (14 ′ .8) divided by the signal-to-noise ratio, which corresponds to < 3 ′ (3.2 kpc at the distance of Cen A) for all sources with a 5σ detection or better. A spectrum was extracted from the data cube at the sky position from which the heliocentric radial velocity, v ⊙ (col.
[4]), was measured at the mid-point at 50% of the peak of emission, and the total flux was determined (col.
[7]) at 50% and 20% of the peak, respectively. The Hi mass (col. [8]) was computed by employing the standard formula: where D is 3.5 Mpc, our assumed distance to the Cen A group.
The examination of the Hanning smoothed spectra ( Figure 2) reveal that none of the detections are marginal. All sources are found to have signals above 3.9 Jy km s −1 . The coordinates of the Hi detections were cross-correlated with the NASA Extragalactic Database and compared with UK Schmidt films to find optical counterparts. Each source could be associated unambiguously with a galaxy (col. [1] of Table 1 ) which is located within the positional uncertainty of 3 ′ radius. In some cases more accurate position informations were acquired with the Compact Array of the Australia Telescope (see Staveley-Smith et al. 1999) where the identifications were always confirmed.
Among the 28 detection we found ten new Cen A group members. Five of these galaxies were previously catalogued but not known to be associated with the group, while the other five were previously uncatalogued galaxies and are identified according to the HiPASS survey nomenclature (HIPASS 1321-31 has recently been detected as 131820.5-311605 by Karachentseva & Karachentsev 1998).
The most gas-rich new group member is ESO 174-G?001 with a Hi mass of M Hi = 2.1 × 10 8 M ⊙ , which is larger than the amount of Hi observed for instance in NGC5253 or NGC5408. It is a low surface brightness galaxy close to the Galactic plane (b = 8 • ) which may explain why its identification as a galaxy was previously uncertain (Lauberts 1982). CEN 5 was previously optically identified and classified as a group member candidate by C97, and so we include the spectrum for completeness, although it is excluded from the statistics by its low velocity (< 200 km s −1 ). Looking at the spectrum (Fig. 2), we see two peaks. However, the higher velocity signal is from the nearby galaxy NGC 4945, the complete profile of which can be seen in Figure 2.
For completeness reasons we also list in Table 1 the Hi limits NGC 5206, ESO 272-G025, and NGC 5128 which remained undetected in this study: NGC 5206 is an early-type galaxy and ESO 272-G025 was classified as peculiar (Lauberts, 1982). These two galaxies were also not detected in Hi emission by C97, to a more sensitive detection limit. Since the Multibeam failed to detect the powerful radio galaxy NGC 5128, the listed Hi mass for this galaxy is taken from de Vaucouleurs et al. (1991), derived from absorbing gas.
In Figure 3 and Figure 4 we compared the total fluxes and velocity-widths (∆V 20 ) with the corresponding data measured by C97. In general we found good agreement, showing HiPASS is achieving the expected sensitivity, although for three galaxies we measured larger integrated fluxes, suggesting that there may be a 21-cm signal outside C97's chosen search areas.

Optical properties
We attempted to get CCD images in the optical photometric bands B and R for those galaxies without reliable photometry in the literature. The optical data was acquired as part of an extensive optical follow-up program of HiPASS galaxies. This program employs three telescopes: (i) the 40-inch telescope at the Siding Spring Observatory, (ii) the 1m Swope Telescope at Las Campanas Observatory, and (iii) the Curtis Schmidt telescope at CTIO. We used 2048 2 CCDs with a ∼ 24 ′ field of view and a pixel size of 0.7 ′′ , except for the Siding Spring observations, where a 800 2 CCD was used with a ∼ 8 ′ field of view and the same pixel size.
For each galaxy a series of 6 exposures of 300 seconds each were taken. The optical data were de-biased and flattened with the standard STARLINK CCDPACK (Draper 1993) reduction techniques, then calibrated using Landolt (1992) standards. The seeing was typically 1 ′′ . In the case of HiPASS 1337-39, we had to rely on the image from the Digitised Sky Survey, DSS 14 (a similar method to that employed by Spitzak & Schneider, 1998) to calibrate an image for which we had no calibrated CCD data. Figure 5 shows B-band images of the newly identified Cen A group galaxies to illustrate the variety in optical morphology. Previously catalogued galaxies (single *) are high surface brightness objects and thus likely to be visually identified as background galaxies. The uncatalogued galaxies (**), on the other hand, are faint, low surface brightness galaxies with small angular size and very hard to see.
In Otherwise the total apparent B magnitude was taken from the literature. Where we could fit an exponential profile µ(r) = µ exp 0 + 1.086(r/r 0 ) to our own optical data we also quote the extrapolated central surface brightness µ 0 (col. [6]) and the exponential scale length r 0 (cols. [7] and [8]). In some cases the galaxy was too faint, or too obscured by stars, for a reliable profile fit to be made.

Results
To summarise our results, a shallow integration Hi survey of the inner 600 square degrees of the Cen A group and the velocity range 200 < v ⊙ < 1000 km s −1 revealed 28 Hi sources which all have been identified as Cen A group galaxies. All detections have integrated flux larger than 3.9 Jy km s −1 . Eighteen objects coincide with previously known group members. A further 10 are suggested as new group members. Of these 10, 5 coincide with previously catalogued galaxies and 5 coincide with previously uncatalogued galaxies. Three main group members were not detected at our survey sensitivity of 10 7 M ⊙ of Hi, assuming an Hi velocity width of 50 km s −1 , but one (NGC 5128) is known as an Hi source from absorption studies. All new galaxies detected in this study have optical counterparts.
14 The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166.
However, this depends on an extrapolation to infinity, and so the model magnitudes should be compared with the m B values in Table 2 obtained from aperture photometry. The galactic extinction A B for each galaxy, given in col.(4), has been obtained from the dust maps of Schlegel et al. (1998), wherein dust is mapped from the energy it emits in the far infra-red as seen in the high spatial resolution observations made with IRAS and DIRBE. In the case of the highly obscured ESO174-G?001 we have checked that estimate by measuring the colours of neighbouring background elliptical galaxies in our frames, and find excellent agreement (± 0.1 magnitudes).
Assuming a mean distance modulus of (m − M ) = 27.8 for the Cen A group (Saha et al. 1995), and correcting for the extinction, we converted the absolute magnitude M B (col. Although M i may be a crude estimator of the true dynamical mass, it should provide a safe lower limit because Hi radii are usually larger than the optical radii. For instance, Bosma (1978) suggests Hi disks extend out to 1.5 × the optical Holmberg radius, while for gas-rich galaxies, the ratio of Hi to optical diameter can be much greater (e.g. van Zee et al. 1995).
The newly found group members fall in two main categories. Of the five previously catalogued galaxies, Indeed, if we look at their ratios of M Hi /L B uncorrected for Galactic extinction we find they have values ranging between 4 and 10, with a median of 5.   but are very rare. If such objects have a stellar mass-to-light ratio M ⋆ /L B = 1, then they contain significantly more mass in the form of gas than of stars, and it will be interesting to investigate what their evolutionary status may be.

The Hi Mass Function
There is considerable controversy over the faint-end slope of the galaxy Luminosity Function (see §1) and thus added interest in the low-mass end of the Hi Mass Function (HiMF). The HiMF has been recently investigated by three different groups (Spitzak & Schneider 1998;Zwaan et al. 1997;and Kilborn, Staveley-Smith & Webster 1998). The first two groups used deep pencil beam samples observed with Arecibo, whereas Kilborn used HiPASS objects to study a flux-limited sample. Each of these surveys contain between 50 and 100 objects but, because they are flux-limited, they contain very few low mass objects, and are therefore not suited to determining the low mass slope. Our survey, on the other hand, being principally distance-limited is much better suited to determining that low-mass slope, though it lacks the higher masses In Figure 6 we plot the Hi mass function from the 27 detections of our survey which have accurate Hi masses.
In order not to over-interpret the data we do not attempt to find a fit for M ⋆ Hi , only to find the faint-end slope α. To do this we make a weighted linear least-squares fit of log ρ against log M Hi (where ρ is the number of sources per log 10 M HI bin) for sources with M Hi < 10 9 M ⊙ ( Figure 6) and find : log ρ = (-0.30 ± 0.15) log M Hi + (3.21 ± 1.20) Hence the Schechter faint-end slope is where the formal error on the slope (see Bevington, 1969) arises from assuming purely Poisson statistics for the numbers in each ρ-bin in Figure 6. Since the most likely systematic error is the loss from our lowest mass bin of sources which did not make the first cut, and therefore were not re-measured more accurately, we can ask how α would change if we added 50% more sources to the 12 already in that bin. In fact α rises to only 1.45 ± 0.15. Similarly the formal error on the slope allows α = 1.45 at 1 standard deviation. Our data therefore does not rule out a faint-end slope of 1.5 but we can exclude a slope as steep as 1.7 at the 95% level. Table 4 contains a comparison of our Cen A results with those from the three other HiMF surveys mentioned above.

Discussion
It is encouraging that the present comparatively shallow blind Hi survey already increases the number of known galaxies of the Cen A group by 50%, i.e. from 20 to 30 in our search area. It is in particular interesting that this happened after the group was so carefully studied in the optical (C97).
A glance at the spectra (Figure 2) confirms that none of our objects are marginal detections. All have signals above 3.9 Jy km s −1 , whereas the formal 5σ noise limit for optimally smoothed sources that are 50 km s −1 broad is closer to 1.5 Jy km s −1 . The dispersion in the velocity of the less significant peaks in our data map mimic the velocity distribution of the Cen A group galaxies, suggesting that many of them will also turn out to be real members of the group.
We find only one low surface brightness galaxy with an Hi mass of more than 10 8 M ⊙ -ESO174-G?001 which contains 2.8 × 10 8 M ⊙ of Hi. It is 3 arc minutes across and its measured central surface brightness is 24.5 µ B , which is indeed low. However, it is the galaxy closest to the Galactic plane (b = 8 • ) and turns out to have 2.1 magnitudes of foreground blue extinction. When this is allowed for, the central surface brightness rises to 22.4 µ B -which is not very low; M Hi /L B drops to 0.8 and the absolute magnitude, M B = −15.6.
ESO174-G?001 was missed by previous studies simply because of the large extinction towards it. Despite its comparatively large size, ESO174-G?001 is still much smaller than the instrument beam. If there were a giant LSB galaxy in the group, i.e. one with a diameter larger than the projected beam (15 kpc), we could only have detected it, on signal to noise grounds, if its projected mass were more than 10 7 M ⊙ of Hi per beam; thus it would need to have a column density, N Hi , of at least 10 19 atoms cm −2 . In reality, our automatic baseline fitting procedure would at present almost certainly "remove" the signal from the data. Irrespective of telescope size, for sources that fill the beam there is a lowest column density detectable by any radio telescope, set by receiver noise, where ∆V is the projected linewidth in km s −1 (e.g. Disney & Banks 1997). Extreme objects, close to this column density limit, are best found when they are matched to the beam. For example, an L ⋆ galaxy ten times the radius of our own and containing the same amount of Hi would have an N Hi < 10 19 atoms cm −2 and would be found only in integrations significantly longer than HiPASS , and most probably out near 6000 km s −1 . So the results from the present Hi survey do not rule out the existence of extended LSB galaxies in the Cen A group. The present study is being followed by a much deeper Hi survey in the same region, using the same instrument to address this issue.
Although our survey has increased the number of known Cen A group members by 50%, the new members add only 6% to the total Hi, and 4% to its light. The Hi mass function has a slope at the low mass end of 1.33 ± 0.15, which is unlikely to be steeper than 1.5 due to either statistical or systematic effects.
The five newly catalogued dwarfs have indicative mass to stellar mass ratios (col. [8], Table 3) between 40 and 80 (mean 63 ± 16). Such ratios probably underestimate the dynamical masses because they assume the Hi radii (R Hi ) are equal to the optical radii (R opt ). However, Hi maps of similar objects by other authors generally show that R Hi > R opt -the most striking example being the VLA observations of Hi1225+01, Chengalur, Giovanelli & Haynes 1995 (for comparison, the five new group members that are previously catalogued have a mean ratio of 14). The high ratios add to the accumulating evidence (e.g. Kormendy 1985) that Hi-rich dwarfs have their dynamics controlled by dark matter.
This survey of the Cen A group was aimed chiefly at validating the performance of the wider HiPASS survey of the southern sky -which will be over 90% complete by the time this goes to press. It confirms that performance matches expectation, and that large area blind Hi surveys will open a new window onto the extragalactic sky. As to the Cen A group itself, we expect to find further new group members when we run the data through the automatic galaxy-finding algorithm now under development. We have also completed a much deeper survey (t obs =12 × HiPASS ) of a limited region (8 • x 4 • ) in the area, to investigate the performance and promise of long multibeam integrations (Banks 1998 interval which is between 200 and 1000 km s −1 . The spectrum of CEN 5 is included for completness but it is excluded from the statistics because its velocity is below our lower limit.    · · · · · · · · · < 5.5 5 ESO 272-G025 3 14 43 26 -44 42 19 620 · · · · · · · · · < 5.5 5 * Previously catalogued but not known to be group members.
1 Not included in the statistics because v ⊙ < 200 km s −1 .
2 Hi mass and linewidths uncertain, galaxy profile confused with HVC.