Clusters of galaxies form a representative population which traces the highest initial density fluctuation peaks. They are excellent tools for exploring the distant Universe and are used to constrain cosmological models. A significant fraction of clusters shows evidence of substructure (e.g. Geller & Beers 1982; Dressler & Shectman 1988; West 1994; for a recent review see Pierre & Starck 1998) and complexity in the distribution of the different constituents - galaxies, gas, dark matter (Baier et al. 1996). Combined multi-wavelength observations are needed to disentangle the dynamical state of clusters. Analysis of the velocity and space distribution of the galaxies is very important but, in contrast to the optical, the X-ray analysis is less prone to projection effects and probes better the cluster mass distribution (because the X-ray surface brightness depends on the square of the matter density). The presence of substructure is also revealed in the radio properties of clusters (Röttgering et al. 1994; Reid et al. 1998), but the radio sources in turn may also influence the X-ray emission (Rizza et al. 2000).

This paper is the third in a series of papers (Pierre et al. 1997; Lémonon et al. 1997) dedicated to studies of distant, bright X-ray clusters discovered in the ROSAT All-Sky Survey (RASS, Voges et al. 1999). A sample of $\approx$ 10 clusters with $L_{\rm X} > 10^{44}$ erg s^-1 was selected (Pierre et al. 1994) in the redshift range 0.1 < z < 0.3. In this paper we present multi-wavelength observations of two of these clusters - Abell 1451 and 1RXS J131423.6-251521 (hereafter shortened to RXJ1314-25). General data associated with both clusters are given in Table 1.

Table 1: Properties of the two clusters. References: Abell (1958), Abell et al. (1989) for the coordinates and richness; Bautz & Morgan (1970) for classification for Abell 1451 ; coordinates for RXJ1314-25 are from RASS (Voges et al. 1999); $T_{\rm X}$ and $L_{\rm X}$ in the 2-10 keV band are from Matsumoto et al. (2001); redshift and $\sigma _{\rm v}$ are from this paper; the apparent magnitude of an L^* galaxy was calculated using M^*(B_j)=-21.8, obtained by adjusting the Lumsden et al. (1997) value of M^*(B_j)=-20.16 to the cosmological parameters used in this paper.
Abell 1451 RXJ1314-25

RA (J2000) 12:03:16.0 13:14:23.6

Dec (J2000) -21:30:42 -25:15:21

BM Class III -

Richness 3 -

Redshift 0.1989 0.2474

$\sigma _{\rm v}$ km s^-1 1330 1100

B_j^* 19.5 20.2

$L_{\rm X}\ (10^{45})$ erg s^-1 1.5 1.8

$T_{\rm X}$ keV 13.4 8.7

**Table 1:** Properties of the two clusters. References: Abell (1958), Abell et al. (1989) for the coordinates and richness; Bautz & Morgan (1970) for classification for Abell 1451 ; coordinates for RXJ1314-25 are from RASS (Voges et al. 1999); $T_{\rm X}$ and $L_{\rm X}$ in the 2-10 keV band are from Matsumoto et al. (2001); redshift and $\sigma _{\rm v}$ are from this paper; the apparent magnitude of an L^* galaxy was calculated using M^*(B_j)=-21.8, obtained by adjusting the Lumsden et al. (1997) value of M^*(B_j)=-20.16 to the cosmological parameters used in this paper.
	Abell 1451	RXJ1314-25
RA (J2000)	12:03:16.0	13:14:23.6
Dec (J2000)	-21:30:42	-25:15:21
BM Class	III	-
Richness	3	-
Redshift	0.1989	0.2474
$\sigma _{\rm v}$ km s^-1	1330	1100
B_j^*	19.5	20.2
$L_{\rm X}\ (10^{45})$ erg s^-1	1.5	1.8
$T_{\rm X}$ keV	13.4	8.7

The plan of the paper is as follows: in Sect. 2 we present optical observations, data reduction, redshift catalogues and data analysis for the two clusters. In Sects. 3 and 4 we present ROSAT-HRI observations and data analysis and ATCA radio observations and data analysis respectively. Finally in Sect. 5 we discuss the multi-wavelength view of Abell 1451 and RXJ1314-25. Throughout the paper we use H₀ = 50 km s^-1 Mpc^-1and q₀ = 0.5.

1 Introduction