HI-observations of dwarf galaxies in the Local Supercluster

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Volume 506 / No 2 (November I 2009)

A&A, 506 2 (2009) 677-680

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Issue		A&A Volume 506, Number 2, November I 2009


Page(s)		677 - 680
Section		Extragalactic astronomy
DOI		https://doi.org/10.1051/0004-6361/200911774
Published online		03 September 2009

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4 Appendix

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Figure A:

1 a)

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Figure A:

1 b) Reproductions of the blue POSS-II survey measure 6' by 6', north is at top, east at left. The dwarf galaxies FS20 and LeG18 are given in the upper image a), while d1217+4708 is shown in the lower picture b).

Around the position of each galaxy in our sample, we examined a region of 9.3 arcmin radius (i.e., twice the half-power beam width of the Effelsberg telescope) using the Digital Sky Survey (DSS), as well as the velocity and other data provided in the NED. Based on this, if we failed to identify one or more likely sources of confusion with the observed HI profile, we accepted the HI profile to be genuinely associated with the targeted dwarf galaxy.

d0245+3955, d0245+3957, and d0246+3952
These irregular galaxies of low surface brightness form a tight triple sub-system inside the NGC 1023 group.

d0946+6842
This faint object of very low surface brightness was discovered by Chiboucas et al. (2009) as a probable background galaxy behind the M 81 group. There is a strong disagreement between its low luminosity and the broad HI line width, leading to $M_{\rm T}$ / $L_{\rm B}$ $\sim$ 184 and $M_{\rm HI}$ / $L_{\rm B} = 30$ in solar units. We carefully inspected its surroundings using POSS-II and SDSS and did not find any suitable optical counterpart to explain the detected HI signal. This object would be an interesting target for a more detailed study.

FS 20 = LeG 19 and LeG 18
These dwarf members of the Leo-I group (Karachentsev and Karachentseva 2004) are separated by $\sim$ 3 arcmin (see Fig. A.1), both being within the antenna beam. LeG 18 was detected within the Arecibo ALFALFA survey as AGC 201970 with $V_{\rm HI} = 636$ km s^-1, W₅₀ = 38 km s^-1, and S = 0.55 Jy km s^-1. FS 20 may be probably identified with AGC 205290 [10 46 42.4 +12 46 58] with $V_{\rm HI} = 915$ km s^-1, W₅₀ =50 km s^-1, and S = 1.46 Jy km s^-1 (Stierwalt et al. 2009). Both objects are within the so-called ``Leo HI ring'' (Schneider et al. 1983).

CGCG 66-109
This is another dwarf member of the Leo-I group (see Stierwalt et al. 2009), for which $V_{\rm HI} = 777$ km s^-1, W₅₀ = 44 km s^-1, and S = 1.74 Jy km s^-1. Its optical velocity, $982 \pm 78$ km s^-1, from the SDSS DR4 corresponds to a blue knot outside the galaxy centre.

d1150+5546
The marginal narrow HI line ( $v = 594 \pm 6$ km s^-1) reported by Karachentsev et al. (2007) lies in a radial velocity range with frequent RFI. Therefore, we included this object in Table 3 (upper limits).

d1217+4703 = BTS 109
This is a new tiny member of the Canes Venatici I cloud (see Fig. A.1) with very high HI-mass-to-luminosity ratio of 6.5, and M_T/ $L_{\rm B} = 29$ in solar units.

d1221+2814 = KK 138
Marginal HI detection. The broad HI line width W₅₀ = 186 km s^-1 yields an extremely high total-mass-to luminosity ratio of $\sim$ 250 in solar units.

d1233+3806 = BTS 142
This object was detected also in a blind HI survey at Westerbork (Kovac et al. 2009); $V_{\rm HI} = 719$ km s^-1, W₅₀ = 47 km s^-1, and S = 0.41 Jy km s^-1.

KKSG 29
This is a probable dwarf companion of NGC 4594 (the ``Sombrero'' galaxy); $V_{\rm LG} = 828$ km s^-1. Assuming a distance of 9.33 Mpc (Ferrarese et al. 2000) for NGC4594 the projected separation of KKSG 29 from NGC 4594 is 218 kpc. A difference in radial velocity of 266 km s^-1 between both galaxies yields an orbital mass estimate of $1.2 \times 10^{13}~M_{\odot}$ or $M_{\rm orb}$ / $L_{\rm B} = 140$ in solar units. There are four other probable dwarf companions to the Sombrero galaxy within 200 kpc, KKSG 31, KKSG 32, KKSG 33, and KKSG 34; which are all of type dSphs and not detected in HI.

d1243+2956 = BTS 152
This object is HI-rich, a suitable target for a detailed study in H $_{\alpha}$ and HI.

d1243+4127
A new dwarf member of the CVn I cloud. It was also detected by Kovac et al. (2009) with $V_{\rm LG} = 436$ km s^-1.

d1312+4147 = KKH 82 = UGCA 337
A new member of the CVn I cloud. Its optical velocity of $529 \pm 40$ km s^-1 (SDSS DR4) agrees well with the HI velocity. However, the broad HI line width of 234 km s^-1 yields an extremely high $M_{\rm T}$ / $L_{\rm B} = 182$ in solar units. No suitable object for confusion could be found within the antenna beam.

Table 3: Observational data - upper limits.

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