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4. Description of tables

The previous selection based only on IRAS data is a first step to get a global list of candidates. However we expect to find in this list many foreground stars as well as some star clusters, and some IRAS candidates could be associated with optically known red supergiants. We also have to remove from this first list IRAS sources which have been identified in previous works as obscured AGB stars or late-type supergiants, through JHKLM photometry. We therefore tried to find counterparts to the IRAS sources of groups 1 and 2. For that purpose we have extensively used the Simbad database, as well as a compilation of most works on AGB stars and M supergiants in the Magellanic Clouds (see references), as some of them have not been entered in the Simbad database (in particular the surveys by Blanco et al. 1980; Westerlund et al. 1978, 1981). Cross-identifications are mainly based on the positions of the objects, but also on the consistency between the optical magnitudes and the IRAS fluxes and colours. For IRAS sources already listed in the PSC, we have searched around 30'' from the IRAS-PSC position; for new IRAS sources not discovered in the PSC we have searched around 60'' as the position given by Schwering & Israel is not more accurate. The IRAS-PSC uncertainty is in principle smaller than 30''. However, as the IRAS flux densities of our sources are often close to the sensitivity limit, the position might be less accurate than usual. In addition, we notice that positions given by Schwering & Israel and Reid et al. sometimes disagree by more than 60''. On the other hand, the JHKL counterpart of obscured AGB stars is generally close (within 20'') to the IRAS-PSC position (see Reid 1991; Zijlstra et al. 1996, Paper II).

Finally, we have divided the IRAS sources into 7 tables which will be described below:

4.1. Tables 1 (click here), 2 (click here), and 3 (click here): identified objects

Optically known red supergiants and AGB stars are listed in Table 1 (click here), obscured AGB stars and late-type supergiants without optical counterparts in Table 2 (click here), and planetary nebulae in Table 3 (click here). Column 1 lists the LI number as given in Schwering & Israel, and Col. 2 the TRM number as given in Reid et al. A "tex2html_wrap_inline1782'' in front of the LI number means that the IRAS source was also found in the PSC. Columns 3 and 4 list the coordinates as found in Schwering & Israel or in Reid et al. (when the TRM source has not been found by Schwering & Israel); note that Schwering & Israel provide coordinates more accurate than 60'' only when the source is also in the PSC, and then they just give the IRAS-PSC coordinates. Columns 5, 6, 7, and 8 list the IRAS flux densities at 12, 25, 60, and tex2html_wrap_inline1756, respectively, as found in Schwering & Israel (or in Reid et al.); "C'' means contaminated, and ":'' means that the value is uncertain. Column 9 and 10 list the IRAS colours, tex2html_wrap_inline1788 and tex2html_wrap_inline1790. Column 11 gives the group (1, 2 or 3) of the IRAS source as defined in Sect. 3. When we give two possibilities for the group, the second value corresponds to the group found by using the Reid et al.'s values if the group is different from the one derived from the Schwering & Israel values (see also Table 8 (click here)). The last column gives the identification: source name, some observational information (between bracket), and a code for references (between square brackets). The list of references is given at the end of the tables, as well as, for Table 1 (click here), an overview of the various optical identifications. Table 1 (click here) lists 52 LMC and 7 SMC optical stars. Table 2 (click here) contains 34 LMC and 2 SMC sources. Among the 34 LMC obscured AGB stars (or late-type supergiants), 16 have been identified recently by Zijlstra et al. (1996, Paper II) on the basis of the present work (for selection) and infrared observations in the JHKL' bands and at tex2html_wrap_inline1626.

The reader will notice that Table 1 (click here) contains 2 sources known to be optically thick, in particular the famous PSC 04553-6825 (LI-LMC 181) discovered by Elias et al. (1986) and Wood et al. (1986). This source has an optical counterpart (WOH G064 in Westerlund et al. 1981, spectral type M7.5 in Elias et al. 1986) and is therefore listed in Table 1 (click here). PSC 00350-7436 (LI-SMC 5) has an optically thick dust shell as well. As Whitelock et al. (1989) could determine its spectral type, a peculiar carbon star, we list it in Table 1 (click here). Other sources in Table 1 (click here) do not have optically very thick dust envelopes.

4.2. Comments on the Wood et al.'s (1992) list

Wood et al. monitored in JHKL 3 sources in the SMC and 16 in the LMC. The results are presented in their Tables 3 (click here) and 5 (click here). Among the 16 LMC sources, we found that PSC 04553-6825 (LI-LMC 181), possibly PSC 05247-6941 (LI-LMC 976), PSC 05261-6614 (LI-LMC 1033), and PSC 05389-6922 (LI-LMC 1470), have a known optical counterpart of spectral type M: WOH G064, WOH SG264, WOH SG281, and WOH SG455, respectively (Westerlund et al. 1981, see Table 1 (click here) caption). They are listed here in Table 1 (click here). PSC 04571-6954 (LI-LMC 225) can be identified with the well know S Dor variable HD 268835 of spectral type B8Ia and is listed in Table 7 (click here). PSC 05244-6832 (LI-LMC 961) and PSC 05325-6743 (LI-LMC 1274) have extremely red IRAS colours and fall in our group 3. They can be identified with the HII regions LHA 120-N 138D and LHA 120-N 57A, respectively (Henize 1956), and are listed in Table 7 (click here). The 3 SMC sources all have very red IRAS colours and fall in group 3 too. There is a probable M supergiant close to PSC 00477-7343 (LI-SMC 57), so we list this source in Table 1 (click here). However we think that the association between the IRAS source and the optical star is doubtful. PSC 00521-7054 is identified with a galaxy and is listed in Table 7 (click here). Finally, for PSC 01039-7305 (LI-SMC 173) we could not find any identification. However, in addition to its unusual IRAS colours, it also has unusual JHKL colours for an AGB star, so we again list it in Table 7 (click here).

Wood et al. also list 14 sources in their Table 4 (click here) that they could detect in JHK. Among them, PSC 05027-7124 (LI-LMC 346), PSC 05198-6941 (LI-LMC 816), and PSC 05280-6910 (LI-LMC 1100), belong to groups 1 or 2. They are however in Table 7 (click here) as associated with the blue supergiant HD 269006, two hot stars, and NGC 1984, respectively. The other objects all belong to group 3 and have very red IRAS colors. We list all of them in Table 7 (click here), either because they are associated with hot stars, or with HII regions, or because the NIR colors are much too blue compared to the IRAS colors. We do not exclude that the NIR colors actually correspond to an AGB star, however the association with the IRAS source is unlikely.

4.3. Tables 4 (click here) and 5 (click here): unidentified IRAS sources

Unidentified IRAS sources from group 1 are listed in Table 4 (click here) (AGB stars, post-AGB stars, and PNe candidates), and those from group 2 in Table 5 (click here) (IRAS data insufficient to conclude on their nature). Columns 1 to 10 are the same as in Tables 1 (click here), 2 (click here), 3 (click here). For some sources we found one or several objects close to the IRAS position, but we think that the association with the IRAS source is unlikely. In particular, we found some IRAS sources close to optical C stars or LPVs, but the IRAS flux densities are much too bright compared to what one expects from the optical and JHKL properties of the stars. Such cases are listed at the end of the Tables. Table 4 (click here) contains 198 LMC and 11 SMC sources, so about 6 times more new obscured AGB stars candidates than what is already known as listed in Table 2 (click here).

4.4. Table 6 (click here): foreground stars

It contains all the sources from groups 1 and 2 found or believed to be foreground stars. The columns are the same as in Tables 1 (click here), 2 (click here), and 3 (click here). Identifications of foreground stars are based on the V (or I) magnitude of the star, and/or its spectral type, and/or its heliocentric velocity. Most of them have M, K, F, G giant or dwarf types. For three sources in the LMC, we did not find any optical star at the location of the IRAS source. However, their location in Fig. 1 (click here) shows that they are very likely foreground stars. Table 6 (click here) contains 135 and 29 stars in the fields of the LMC and the SMC, respectively.

4.5. Table 7 (click here): ruled out objects

It contains all the sources, from groups 1 and 2, that we have ruled out after the selection described in Sect. 3. They are mostly associated with star clusters, or/and hot stars, Wolf-Rayet stars, or blue luminous variables; there are also a few HII regions and galaxies. Table 7 (click here) contains 76 LMC and 15 SMC sources, including the group 3 sources from Wood et al. (1992, see Sect. 4.2).

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