The resulting HI spectra of all 23 M 81 group candidate dwarf galaxy members are shown in Fig. 2 (click here).
Figure 2: 21cm HI line spectra of all 23 candidate dwarf galaxy members of the M 81 group observed. Velocity resolution is 12.7 . For each object two panels are shown, with the upper displaying a small range in flux density to reveal faint features, and the lower giving the full intensity range to demarcate the Galactic HI features (typically at as well as confusion in the HI complex surrounding M 81, in the range -280 to +355 , cf. Yun et al. 1994). Radial velocities are according to the radio convention
The optical centre positions to which the telescope was pointed, the rms noise of the spectra at 12.7 resolution, as well as derived HI line properties are listed in Table 2 (click here). Upper limits to the HI line flux are 3 values for an assumed line width of 50 . The last two columns indicate the velocity range within which the strong Galactic HI line signal prevents detection of external galaxies (typically ), or the strong emission of the interconnected HI distribution around the galaxies M 81, M 82, NGC 3077 and possibly NGC 2976 obliterates the lower flux emission of the 6 dwarf candidates in that vicinity, i.e. a detection of Kar 2N, Kar 3N, A952+69, Kar 61, Garland and Kar 5N in the velocity range -280 to +355 (cf. van der Hulst 1977; Appleton et al. 1985, and Yun et al. 1994 for detailed HI maps of this complex region).
|(h m s)||( )||(mag)||(km/s)||(mJy)||(km/s)||(Jy km/s)||(km/s)||(km/s)||(km/s)|
|6.||U 4998||09 20 53||68 35 53||dS0:||13.9||3.1||632||0.67||89||105||-90||140|
|8.||Kar 1N||09 41 00||69 37 00||Im||15.5||3.5||570||3.05||56||81||-120||75|
|10.||Kar 2N||09 43 42||69 30 00||dE?||15.9||3.5||<0.52||-115||250|
|11.||Kar 59||09 46 40||72 17 41||Im||17.1||4.0||(1322||27.7||311||326)||-110||100|
|12.||Kar 3N||09 49 42||69 12 00||Im||17.1||-40||4.0||<0.60||-280||290|
|15.||A952+69||09 53 27||69 31 18||Im||14.3||3.1||<0.47||-270||355|
|16.||Kar 61||09 53 01||68 49 48||dE,N||13.8||3.4||<0.50||-260||190|
|19.||Garland||09 59 54||68 55 30||Im||50||3.8||<0.58||-170||75|
|20.||Kar 5N||10 00 42||68 30 00||dE:||18.1||3.6||<0.54||-195||130|
|21.||DDO 71||10 01 18||66 47 53||dE,N||14.6||-126||3.4||<0.50||-160||150|
|23.||Kar 64||10 03 07||68 04 20||dE,N||14.9||4.3:||<0.65||-115||130|
|24.||DDO 78||10 22 48||67 54 40||dE||14.3||4.9||<0.74||-145||90|
|25.||U 5658||10 23 53||71 29 34||Im||15.0||4.0||1159||1.20||127||203:||-155||35|
|27.||DDO 82||10 26 48||70 52 33||Sm||11.8||40||3.4||<0.50||-135||100|
|28.||Kar 6N||10 31 00||66 16 00||dE||16.0||4.4:||<0.79||-170||65|
|30.||UA 220||10 46 04||64 59 00||Im:||16.9||3.1||<0.47||-180||115|
|33.||Kar 7N||10 47 06||65 22 00||?||16.2||4.3||<0.65||-175||75|
|36.||Kar 73||10 49 30||69 48 55||Im||14.9||115||4.3||<0.65||-165||165|
|37.||Anon 5||10 50 30||65 31 00||?||15.5||2.3||<0.34||-100||80|
|38.||Anon 6||10 50 54||65 17 00||?||16.1||2.8||<0.41||-55||50|
|39.||Kar 8N||10 51 06||65 28 00||?||15.4||3.6||<0.54||-50||45|
|40.||Anon 7||10 51 18||65 33 00||?||15.8||2.2||<0.32||-165||70|
|41.||Kar 74||10 59 05||70 32 01||dE/Im:||15.2||3.1||<0.47||-165||60|
In the search for objects that may possibly have confused the 4 HI line spectra in which the profile of an external galaxy was detected (i.e., of UGC 4998, Kar 1N, Kar 59 and UGC 5658) we queried the NED database in an area of (), i.e. 1.5 times the HPBW in both R.A. and Dec.
No. 6 = U 4998 A photograph is displayed in the photographic atlas of Karachentseva et al. 1985a (forthwith KKB85), obtained with the 6 m SAO telescope, who suggest a dE7 classification. The structural parameters from photometry based on scans of plates from the 2 m Tautenburg Schmidt telescope and the above KKB85 atlas are given in Karachentseva et al. (1987), henceforth KKRBF87. The Nançay observations reveal a clear detection at 631 . The earlier HI observations by Fisher & Tully (1981, henceforth FT81) were not sensitive enough and the signal discovered here is outside the velocity range covered in the Green Bank 90-m HI survey of Schneider al. (1992) (henceforth STMM92). Within the search area no other galaxies are known, only a radio source (87GB 092050.8+68181) at 177 distance. The detection at Nançay at 631 hence suggests that this dwarf candidate is not a member of the M 81 group but lies behind the M 81 group.
No. 8 = Kar 1N = Mailyan 45 The positional agreement - later confirmed by Madore et al. (1994) - and corresponding dimensions suggest this galaxy to be the dwarf Mailyan 45 discovered earlier (cf. Mailyan Dwarf Galaxy Catalog, Mailyan 1973). A photograph and isodensity map is given in KKB85 who suggest that this very elongated object might be interacting with the intergalactic medium, as its light distribution is noticeably lopsided. The Nançay\ observations find a clear detection at 569 . No objects which might cause confusion were found in NED, only a radio source (87GB 094123.3+692131) at 157 distance, and a faint 60 m source (IRAS F09413+6914) at a distance of 222. This irregular galaxy is thus more distant than the M 81 group.
No. 10 = Kar 2N Photograph in KKB85. No structural details can be seen. Note the strong negative (residual) emission between 0 and 200 in the spectrum given in Fig. 2 (click here). This emission is due to the higher velocity gas of the western part of M 81 entering through the sidelobes of the Nançay radio telescope. If this object were to have some gas in this velocity range it would not be detectable with these observations.
No. 11 = Kar 59 Photograph of this very faint low-surface brightness object is given in KKB85, its structural parameters in KKRBF87. Our HI spectrum shows higher noise in the 170 to 250 range, due to interference in the H polarization during these observations; but the other data (V polarization) do not show a detection in this velocity range either. The strong, double-horned profile visible in the spectrum at 1323 is due to NGC 2985, a 11.2 mag Sab spiral at 135 distance (526, ), just outside the area searched in NED (in which no objects were found). For an HI line profile of NGC 2985, see Oosterloo & Shostak (1993). KKRBF87 classify this object as a dwarf spheroidal rather than an irregular which might explain the non-detection in HI.
No. 12 = Kar 3N The photograph by KKB85 and Tikhonov & Karachentsev (1993) shows resolution into blue stars. The latter determined a photometric distance of 2.8 Mpc from the brightest stars. KKB85 consider it to form one tidally-disrupted object together with two small fragments about 1'-2' north of it. Kar 3N might well be HI-rich, but this irregular dwarf lies within the extended HI envelope of M 81 (cf. Yun et al. 1994) and any emission from the dwarf within 355 will be lost in the strong and broad emission from M 81 itself (cf. Fig. 2 (click here)). VLA HI imaging (Westpfahl & Puche 1994) shows a structure like an edge-on disc with a central hole; the velocity field shows systematic rotation, but it is not clear if this is due to the local M 81 arm or to internal motions in Kar 3N.
No. 15 = A952+69 The photograph in KKB85 shows a very low-surface brightness object with clumpiness indicative of star formation. It was resolved into stars with the 6m telescope by Efremov et al. (1986). Again the non-detection of this Im galaxy with the Nançay\ radio telescope does not necessarily imply this galaxy to be gas-poor. VLA synthesis observations in D-array by Yun et al. (1994) in an area of 1.5 around the galaxy M 81 reveals a concentration of HI at the position of this irrregular galaxy (their concentration II), suggestive of an HI mass of =3.0 108 (at the adopted distance of 4 Mpc to the M 81 group). The mean velocity of this gas clump is about 100 with a width of about 30 \ (see also van der Hulst 1977; Appleton et al. 1981). With the single dish observation obtained here this signal cannot be resolved from the much stronger emission of M 81.
No. 16 = Kar 61 = A0961+68 = Mailyan 47 A photograph is given in Bertola & Maffei (1974), an isodensity map in KKB85, the luminosity profile and structural parameters in KKBRF87. This is a typical example of a low-surface brightness dwarf spheroidal system and the non-detection at Nançay is not surprising. However, the analysis by Appleton et al. suggest that this dwarf spheroidal is associated with a clump of HI gas of the order of with a mean velocity of about and a linewidth of 35 . This clump is visible in the more detailed HI map by Yun et al. (1994), but it looks more like the end of a spiral arm than a distinct HI concentration. In either case, the expected signal would not be sufficiently strong to stand out over the HI complex (cf. also Fig. 3 (click here)).
Figure 3: A comparison of spectra obtained exactly at the optical centre of the two objects (No. 15, A952+69 and No. 16, Kar 61) with offsets of one beam width (4') due East and West. The fact that the line profiles are so similar makes it impossible to disentangle the expected much fainter contribution of the dwarf from the signal which is due to the Galaxy and the M 81 complex
No. 19 = Garland Deep photographs, spectra and a detailed discussion of this dwarf irregular are presented in Karachentseva et al. (1985b). The total extent of the object is about 6 and its centre lies about from that of NGC 3077, which has an about 55 lower redshift. It shows various knots of star formation and lies in the extension of the HI bridge connecting NGC 3077 to M 81. Garland may be at an intermediate stage in the conversion of a tidal tail or bar into an ordinary dwarf galaxy as a result of the interaction between M 81 and NGC 3077. Its internal motions are of order 55 and its dynamical age is estimated to be about 108 years only. The HI distribution within NGC 3077 shows an extension to the SE. This might be associated with Garland. The signal in our spectrum primarily originates from NGC 3077 (V = 14 , = 93 ).
No. 20 = Kar 5N The faintest object in our sample (= 18.1). It is round and without structural details (cf. KKB85). It is outside the HI complex around M 81, hence any gas emission could only reside within the narrow velocity range of the Galactic gas.
No. 21 = DDO 71 = Kar 63 = UGC 5428 = Mailyan 49 The photograph in KKB85 finds DDO 71 to be a circular, structureless, very low-surface brightness object. It was not detected in the earlier HI work by FT81 with rms noise of 18 mJy, or at Green Bank (STMM92) with an rms of 8.5 mJy. It is not found in co-added IRAS data either (Melisse & Israel 1994). Based on its optical radial velocity (V = -126 ) and the Galactic gas emission as seen in the spectrum, its HI emission - if present - should have been measurable.
No. 23 = Kar 64 = UGC 5442 = Mailyan 50 A photograph and isodensity map are given in KKB85. Not detected previously by STMM92.
No. 24 = DDO 78 The photograph in KKB85 shows a circular, very low-surface brightness object. Not detected by FT81.
No. 25 = U 5658 = Mailyan 53 The overexposed photograph in KKB85 shows a high-surface brightness object with a regular elliptical outline, partially resolved into knots surrounded by diffuse material. This low flux object was not detected in the earlier less sensitive HI surveys (FT81 & STMM92). The NED search finds two galaxies in the 1.5 times the HPBW area, but they do not appear to be related to our HI line detection: CGCG 333-030, a 15.7 mag object of unknown morphological type and redshift, at 89 distance (, ), and UGC 5645, a 16 mag SBb spiral at a redshift of 10 490 , at 112 distance (, ).
No. 27 = DDO 82 = UGC 5692 The photograph in KKB85 shows a dwarf spiral galaxy with a very distorted spiral structure. Its optical spectrum shows bright H and [SII] lines (Karachentsev & Karachentseva 1984) yielding a recesson velocity of V = 40 . Note, that the radial velocity of 180 listed in the NED database and elsewhere is wrong, since the solar motion has been corrected for twice (Karachentsev et al. 1994). A distance of 4.5: Mpc was derived from photometry of its brightest stars (Karachentsev et al. 1994). Its morphology, the distance and its detection at 60 and 100 m in co-added IRAS data (Melisse & Israel 1994) strongly suggest this galaxy to be HI-rich. But it was not detected in the present Nançay survey, nor in the earlier surveys (FT81, STMM92), nor in a short Westerbork interferometer observation (Kamphuis et al. 1996). This can only be explained, if the gas is at the same velocity as the optically obtained velocity (V = 40 ) rendering detection impossible due to Galactic HI emission.
No. 28 = Kar 6N The photograph and isodensity map in KKB85 show it to be a low-surface brightness object with an axial ratio of 0.5, hardly any luminosity gradient and no structural detail.
No. 30 = UGCA 220 = Mailyan 58 The KKB85 photograph reveals a diffuse, lumpy object with patches of different surface brightness suggestive of star formation and presence of HI gas. This galaxy was not detected at Nançay, nor earlier by FT81. It may be part of the clustering of peculiar low-surface brightness objects, 5 of which were included in our present observing program.
No. 33 = Kar 7N The KKB85 photograph shows a diffuse, patchy faint object. Belongs to the group of unusual objects discovered by Börngen et al. (1984).
No. 36 = Kar 73 Photographs in KKB85 and Tikhonov & Karachentsev (1993) find this galaxy to be resolved into separate knots (stars and HII regions?) superimposed on a diffuse, very low-surface brightness background. Tikhonov & Karachentsev determine a photometric distance of 4.0 Mpc from the brightest stars. VLA HI imaging (Westpfahl & Puche 1994) shows a structure resembling an edge-on disc with a central hole; the velocity field is too complex to discern systematic rotation.
No. 37 = Anon 5 Belongs to the group of peculiar objects. Photograph in Börngen et al. (1984).
No. 38 = Anon 6 Belongs to the group of peculiar objects. Photograph in Börngen et al. (1984).
No. 39 = Kar 8N Diffuse, patchy object of large angular size, at the detection limit of the 6m photograph in KKB85. Belongs to the group of unusual objects reported by Börngen et al. (1984).
No. 40 = Anon 7 Belongs to the group of peculiar objects. Photograph in Börngen et al. (1984).
No. 41 = Kar 74 The photograph (cf. KKB85) shows a featureless object of regular elliptical shape.