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Appendix A: The HIFI beam pattern

The HIFI beam pattern (size, efficiency, etc.) is described by Roelfsema et al. (2012). In October 2014, a release note was issued by the HIFI calibration team (Mueller et al. 2014⁹) reporting improved measures of the half-power beam width (HPBW) and main-beam efficiency (η_mb) that supersede previous estimates in Roelfsema et al. (2012). The new efficiency estimates are systematically lower than previous values by typically 15−20% for η_mb.

For convenience, we reproduce again in this appendix the updated values of the relevant beam-model parameters provided by Mueller et al. (2014) in Tables 2 and 3 of their release note. These values, given in Table A.1, are used to obtain the formulae (Eq. (2) in Sect. 2.2) that describe the frequency/wavelength dependence of HPBW and η_eff for the HIFI bands (1 through 5) used in this work. Since we average the H and V polarization data to obtain final spectra, we use the average of η_mb for H and V at a given frequency in order to convert antenna temperatures () to a main-beam scale (T_MB) at that frequency. We recall that, as stated in Sect. 2:

Appendix B: Additional material

In this Appendix, we include additional material for the ion SO⁺ and the molecule ¹³CO in OH 231.8.

In Fig. B.1, we show all the SO⁺ transitions (detected and nondetected) observed within the frequency range covered in our survey with the IRAM 30 m telescope. Some of the SO⁺ lines are blended with transitions of other molecules and/or are in particularly noisy regions and have not been considered for the rotational diagram analysis presented in Sect. 4.1.

A total of nine ¹³CO transitions have been detected in OH 231.8 from our surveys with IRAM 30 m and Herschel (Fig. B.2 and Table B.1). The ¹³CO lines, which are good tracers of the density and kinematics of the nebula, show structured

profiles with two main components: (1) a prominent, relatively narrow core (centered around the systemic velocity of the source, ~ 33−34 km s^-1) plus weaker, broad wings. The line core arises at the slow, dense central (low-latitude) parts of the nebula, which expand at relatively low velocities of ~10−35 km s^-1 (clump I3), whereas the wing emission mainly arises at the fast, bipolar lobes (see Sect. 1 and Fig. 1). (As explained in the Introduction, the spatio-kinematic structure of the molecular outflow of OH 231.8 is well known from previous single-dish and interferemtric maps of ¹²CO). The large core-to-wing intensity ratio of the ¹³CO profiles is consistent with most (~70%) of the mass in the molecular outflow being in the slow central regions (Sánchez Contreras et al. 1997; Alcolea et al. 2001).

The ¹³CO wing emission progressively weakens, relative to the core, at higher frequencies. For transitions observed with the same telescope (i.e., for the three J_u ≤ 3 lines observed with IRAM 30 m or for the six J_u ≥ 5 lines observed with Herschel), this trend is partially explained by the smaller beam and, thus, the smaller fraction of the fast outflow sampled by the observations at higher frequencies. However, this is not the only reason, since at all frequencies the Herschel beam is comparable to, or larger than, the IRAM 30 m beam, with a maximum size of HPBW = 22.̋1 at 110 GHz for the observations reported here.

Both the full width of the wings and the full width at half maximum of the ¹³CO profiles decrease as the upper energy level increases. The full width of the wings is largest for the ¹³CO (J = 1−0) transition, which is observed over a velocity range of V_LSR = [−80:+140] km s^-1 with a beam HPBW = 22.1′′, and decreases for higher-J transitions down to V_LSR = [+15:+55] km s^-1  for the J = 7−6 line, observed with a comparable beam of HPBW = 27.6′′; for transitions with J> 7, we do not detect wing emission. The FWHM of the ¹³CO lines ranges between ~36 to ~14 km s^-1 for the J = 1−0 and the 10−9 transitions, respectively. An analogous behavior is observed in most molecules observed in our surveys with IRAM 30 m and Herschel, including ¹²CO (Sánchez Contreras et al. 2014; Sánchez Conteras et al., in prep.). The observed trend suggests that the envelope layers with higher excitation conditions (i.e., warmer and, thus, presumably closer to the central star) are characterized by lower expansion velocities.

	Fig. B.1 IRAM 30 m spectra toward OH 231.8 near the five mm-wave doublets of SO+ (see Table 1). An LTE model compatible with values in Table 2 and adopting an average FWHM = 55 km s-1 for the lines is overplot (red line).
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	Fig. B.2 13CO transitions detected in OH 231.8+4.2 with IRAM 30 m and Herschel. The red broad shoulder observed in the 13CO (J = 8−7) line is probably an artificial feature due to residual baseline distorsion.
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© ESO, 2015