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J1254-2900 | Is associated with the dominant cD galaxy in A3528N and is |
J1254-2900 | completely embedded within the envelope of the optical galaxy. |
J1254-2900 | Reid et al. (1998MNRAS.296..531R) classified this source as double, |
J1254-2900 | and high-resolution and high-frequency observations carried out |
J1254-2900 | with the Very Large Array (VLA) and ATCA (Venturi et al. in prep.) |
J1254-2900 | confirm that it is a mini-FR II radio source, with a radio nucleus |
J1254-2900 | and two jets culminating in hot spots, though its total power falls |
J1254-2900 | within the range of FR I radio galaxies. The source has a |
J1254-2900 | moderately steep spectrum over the frequency range of our |
J1254-2900 | observations, i.e. {alpha}^13^_22_=0.9. |
J1254-2901a | Was classified as a head-tail radio galaxy by Reid et al. |
J1254-2901a | (1998MNRAS.296..531R), who also postulated that the radio source |
J1254-2901a | may have been triggered by the passage of the galaxy close to the |
J1254-2901a | cluster centre. Inspection of the superposition between the radio |
J1254-2901a | image and the Digitized Sky Survey (Fig. 5) reveals that the radio |
J1254-2901a | peak is displaced from the centre of the optical counterpart. This |
J1254-2901a | is most likely a resolution effect, i.e. the nucleus of the radio |
J1254-2901a | emission is not coincident with the peak of our 22- and 13-cm |
J1254-2901a | images, but it could also be interpreted as an extreme effect of |
J1254-2901a | ram pressure exerted on the radio emission resulting from the |
J1254-2901a | galaxy motion through the very dense medium in the centre of |
J1254-2901a | A3528N. The source is extended ~60kpc east-west. The total spectral |
J1254-2901a | index of this source, computed in the range of frequencies |
J1254-2901a | presented in this paper, is {alpha}^13^_22_=1.2. We point out that |
J1254-2901a | it should be considered an upper limit, because the lack of short |
J1254-2901a | spacings at 13cm is likely to lead to an underestimate of the |
J1254-2901a | extended flux density. Furthermore the incomplete separation of |
J1254-2901a | this source from J1254-2900 at 22cm adds uncertainties in the |
J1254-2901a | 22-cm flux density. |
J1254-2901b | R=3.03 for this identification, however we consider it reliable |
J1254-2901b | because the rad io emission is extended (see Table 3) and the |
J1254-2901b | optical counterpart falls within the radio isodensity contours. |
J1254-2904 | Is a very interesting radio galaxy in A3528N. The source is |
J1254-2904 | ~4arcmin away from the cluster centre, in the region where the |
J1254-2904 | shock front between the two merging systems A3528N and A3528S is |
J1254-2904 | expected to be located (Schindler, 1996MNRAS.280..309S). The 13-cm |
J1254-2904 | image shows an extension in the direction of the galaxy #2063 (see |
J1254-2904 | also fig. 3 of Reid et al., 1998MNRAS.296..531R). On the assumption |
J1254-2904 | that this is the host galaxy we classify the radio source as a |
J1254-2904 | narrow-angle tail. This hypothesis is confirmed by observations at |
J1254-2904 | higher frequency and resolution (Venturi et al., in prep.), where |
J1254-2904 | the radio core is clearly detected. We therefore confirm the |
J1254-2904 | reliability of the tentative optical identification proposed by |
J1254-2904 | Reid et al. (1998MNRAS.296..531R). The source is extended |
J1254-2904 | ~1.5arcmin (i.e. ~65kpc). Its spectrum is steep in the range |
J1254-2904 | 13-22cm, i.e. {alpha}^13^_22_=1.3, and flattens at lower |
J1254-2904 | frequencies. If we consider the VLA 92-cm flux density (Schindler, |
J1254-2904 | 1996MNRAS.280..309S) and the MOST 36-cm data (Reid et al., |
J1254-2904 | 1998MNRAS.296..531R), we derive {alpha}^36^_92_=0.5 and |
J1254-2904 | {alpha}^22^_36_=1.1. We stress that the spectral index |
J1254-2904 | {alpha}^13^_22_ should be considered only an upper limit to its |
J1254-2904 | true value, because its extended morphology suggests that we may |
J1254-2904 | have lost extended flux at 13cm as a result of the poor short |
J1254-2904 | spacing u-v coverage of the present observations. |
J1254-2913 | Is the second most powerful radio galaxy in the A3528 complex and |
J1254-2913 | it is associated with the dominant cD galaxy in A3528S. The radio |
J1254-2913 | source is dominated by a strong compact component surrounded by |
J1254-2913 | extended emission, the shape of which is reminiscent of wide-angle |
J1254-2913 | tail sources (see also Reid et al., 1998MNRAS.296..531R). Its size, |
J1254-2913 | ~35x20kpc, barely exceeds the optical extent of the associated |
J1254-2913 | galaxy. Using the data at other wavelengths available in the |
J1254-2913 | literature (Reid et al., 1998MNRAS.296..531R, and Schindler, |
J1254-2913 | 1996MNRAS.280..309S) we derive a spectral index 1.0, constant |
J1254-2913 | within the errors, in the range 92-13cm. |
J1254-2916 | is the weakest extended radio galaxy in the A3528 complex. The |
J1254-2916 | higher resolution 13-cm image (Fig. 6), together with the 92-cm VLA |
J1254-2916 | image from Schindler (1996MNRAS.280..309S), suggests that the |
J1254-2916 | source is a head-tail, with a faint compact component coincident |
J1254-2916 | with the associated cluster galaxy. Higher frequency and resolution |
J1254-2916 | observations (Venturi et al., in prep.) confirm that this is the |
J1254-2916 | nucleus of the radio galaxy. From our flux density measurements we |
J1254-2916 | derived a total flat spectrum with {alpha}^22^_13_=0.41. The source |
J1254-2916 | has low surface brightness and diffuse morphology in both bands |
J1254-2916 | presented in this paper, and comparison with the 20-cm total flux |
J1254-2916 | density obtained from inspection of the NVSS suggests that we may |
J1254-2916 | have lost extended flux both at 22 and 13cm. For this reason we |
J1254-2916 | believe that the derived spectral index should be taken with care. |
J1254-2916 | We point out that for the other extended sources we are presenting |
J1254-2916 | in this section, the NVSS 20-cm and the ATCA 22-cm flux density |
J1254-2916 | measurements are in good agreement (see Section 3.2). Given the |
J1254-2916 | uncertainty in the spectral index value, we defer any estimate of |
J1254-2916 | the physical parameters in J1254-2916 to a future paper. |
J1257-3021 | Is the most powerful radio galaxy in the A3528 complex, and is |
J1257-3021 | associated with the brighter nucleus of the dumb-bell galaxy |
J1257-3021 | located at the centre of A3532 (see Fig. 7). Its radio morphology |
J1257-3021 | is intermediate between FR I and FR II radio galaxies, consistent |
J1257-3021 | with its 22-cm total radio power. The peculiar asymmetric shape of |
J1257-3021 | the tails suggests that it could be a wide-angle tail source with |
J1257-3021 | its emission in a plane closely aligned with the line of sight to |
J1257-3021 | the observer. The core of the radio emission is undetectable both |
J1257-3021 | at 22cm and in the full-resolution 13-cm image. We used the 6-cm |
J1257-3021 | flux density value for this source given in Gregorini et al. |
J1257-3021 | (1994, Cat. <J/A+AS/106/1>), and computed the spectral index over |
J1257-3021 | the range 6-22cm, obtaining {alpha}~0.85, typical for this type of |
J1257-3021 | radio source. |
J1254-3042 | The 22-cm image of the radio source J1254-3042, shown in Fig. 8, is |
J1254-3042 | suggestive of a double-double type morphology (Lara et al., |
J1254-3042 | 1999A&A...348..699L) in the shape of a wide-angle tail; however, |
J1254-3042 | the optical identification is unclear, because two very faint |
J1254-3042 | objects coincide with the two inner peaks of the radio emission |
J1254-3042 | (see Table 4). From the 13-cm natural weighted image shown in |
J1254-3042 | Fig. 9, it is clear that the source is very asymmetric in this |
J1254-3042 | band, with the eastern lobe much fainter than the western one. |
J1254-3042 | We tentatively classified the radio source as a WAT. |
J1255-2934 | Has a typical FR II morphology, with a one-sided jet and two |
J1255-2934 | hotspots with similar flux density. The full resolution 13-cm image |
J1255-2934 | is given in Fig. 10. A very faint optical counterpart (see Table 4) |
J1255-2934 | is visible, close to the central radio peak between the two hot |
J1255-2934 | spots, but the identification with this object is uncertain. It is |
J1255-2934 | possible that the counterpart responsible for the radio emission is |
J1255-2934 | an absorbed high-redshift galaxy. |
J1256-3009 | The 22-cm radio density contours of J1256-3009 are shown in Fig. 11, |
J1256-3009 | superimposed on the DSS optical frame. This radio source has a |
J1256-3009 | linear morphology, with an extension of ~1.5arcmin. It is located |
J1256-3009 | north of the axis connecting the centres of A3530 and A3532, at a |
J1256-3009 | distance of ~14arcmin from the centre of A3530 and ~19arcmin from |
J1256-3009 | the centre of A3532. The DSS optical image shows the presence of a |
J1256-3009 | few faint optical objects in the vicinity of the radio emission, |
J1256-3009 | but none of them is obviously associated with the radio source. |
J1256-3009 | Unfortunately the source was not detected at 13cm, possibly because |
J1256-3009 | of its low surface brightness combined with lower sensitivity at |
J1256-3009 | its distance from the field centre (field #3), therefore no hint |
J1256-3009 | about its nature can be derived from the spectral index |
J1256-3009 | information. The source could be a double-double powerful radio |
J1256-3009 | galaxy associated with a distant object fainter than the DSS limit. |
J1256-3009 | Another possibility is that J1256-3009 is diffuse cluster emission |
J1256-3009 | within the Shapley Concentration. On this hypothesis the source |
J1256-3009 | would be ~60kpc in extent, with a power logP_22cm_(W/Hz)=22.87. We |
J1256-3009 | point out that J1256-3009 lies in the region where a merging shock |
J1256-3009 | arising from the interaction between A3530 and A3532 is expected. |
J1256-3009 | We plan to extend our study of this source in order to disentangle |
J1256-3009 | its nature. |