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Figure 1: Emission and absorption spectra toward B0355+508 aka NRAO150. Top panel: 1 HPBW J=1-0 12CO and 13CO profiles from the former NRAO 12 m telescope on a R* brightness scale and the 22.5 -resolution IRAM 30 m 12CO profile from the present work on a main-beam brightness temperature scale. Bottom: IRAM PdBI absorption profiles from various representative species. The profiles have been shifted vertically and scaled in some instances.

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In the text

Figure 2: Evolution of J=1-0 12CO brightness with angular resolution. At bottom, the profile from the former NRAO 12 m telescope is compared with hybrid synthesis data convolved to 1 HPBW. At top the hybrid data centered on the continuum source are displayed at full (5.8 ) and 30 m (22.5 ) resolution. Note that the hybrid synthesis profile much more closely resembles the absorption spectra shown in Fig. 1 at bottom.

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In the text

Figure 3: Summary of mapping information of the diffuse gas around NRAO150. Each panel shows the 12CO emission integrated over the velocity range of one absorption feature visible in Fig. 1, i.e. from top to bottom the -17.5, -14, -10.5, and, combined, the -4.5 and features. The position of NRAO150 is marked by a cross at the map center. The left and middle columns show respectively the 12CO J =2-1 and J =1-0 emission observed with the 30 m singledish antenna while the right column shows the 12CO J =1-0 emission at higher resolution from hybrid synthesis data (i.e. the combination of the 30 m and PdBI instruments). The 30 m 12CO J =2-1 map has been smoothed to . The field of view of the hybrid synthesis maps is about half that of the singledish data: As a guide, the red circle has the same 45 -radius in all panels. The resolution of the hybrid synthesis data (5.8 ) is almost 4 times better than that of the singledish data, 22.5 . Contour levels are spaced by 2 , but for the first contour for the singledish maps which is at 1 . Contour levels are shown on the intensity look-up tables.

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In the text

	Figure 4: Hybrid synthesis CO J=1-0 (5.8 resolution) profiles at selected locations of particularly strong emission. Top: profiles selected from a map of peak emission near . Bottom: selected from a map of peak emission near . Profiles are labelled by their displacement in arcseconds relative to the continuum source.
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In the text

Figure 5: Top: probability distribution function of the line brightness in the hybrid synthesis, normalized to unit area. Bottom: fractional area (cumulative distribution) of pixels whose line brightness is higher than the value given on the abscissa. Right: for the component at . Left: for the -10.5 and components. The histograms have been computed in the line wings (blue curves), the line cores (red and green curves) and baseline devoid of signal (black curve). For reference, the averaged spectra are shown as inset with the same color scheme. The vertical dotted lines display the line brightness medians.

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In the text

	Figure 6: Mean profiles ( , red lines) and rms spatial brightness fluctuation in excess of the random noise rms ( , shaded histrogram). Left: for the 5.8 resolution hybrid synthesis data (random noise: 0.47 ). Right: for the 30 m OTF mapping data at 22.5'' resolution (random noise: 0.33 ).
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In the text

Figure 7: Position-velocity diagrams across and along the main trunk feature at a position angle of -50. Top, left: integrated intensity map of 5.8 -resolution hybrid synthesis data summed over the disjoint velocity ranges and . Contours are shown at levels 5, 10, 15, ...35 . The position of NRAO150 is marked by a cross at the map center. Bottom, left: a position-velocity diagram along the perpendicular strip p through the position of NRAO150 at 5.8 resolution. Contours are shown at levels 0.5, 1, 2, 4, 6, 8, 10, 12 . Top, right: longer position-velocity diagram at 22.5 resolution straddling strip d, made from 30 m data. Contours are shown at levels 0.5, 1, 2, 4, 6, 8, 10, 12 . Bottom, right: position-velocity maps at 5.8 resolution along strips a-f. Coordinates are displacement in right ascension relative to NRAO150. Strip d precisely crosses the continuum source.

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In the text

Figure 8: Joint distributions of the emission of 12CO J =2-1 and J =1-0. The value at a given position of these joint histograms is the number of pixels of the input images whose intensities lye in the respective vertical and horizontal bins. Contour levels are set to 1, 2, 4, 8, 16, ... 512 points per pixel. The joint distributions have been computed and plotted for each velocity components. A (red) line of slope of 0.725 is shown for reference. Only the emission around in the rightmost panel departs noticeably from the mean behavior.

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In the text

Figure 9: Non-LTE models of CO brightness. The kinetic temperature, molecular hydrogen and carbon monoxide abundance are self-consistently determined for gas spheres of constant total density n(H) = n(H I) + 2 n(H2 ) = 64 ... 512 as labelled. The CO line brightnesses are found from microturbulent radiative transfer across the faces of individual models. Each series of points shows the result for a different central column density varying in steps of 2 over the range . A slope of 0.725 is shown by a dashed (red) line.

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In the text

Figure 10: Finer-scale singledish maps of integrated 12CO brightness. The 30 m on-the-fly mapping observations used as short-spacing input to the hybrid synthesis are summed over the 5-channel (1.015 ) intervals most closely centered about the velocity indicated at the upper left in each panel and the integrals are scaled down by 1/1.015 to reflect mean brightness over a 1 -wide interval. Contours are shown at levels 1, 2, 4, 6, 8, 10 . The position of NRAO150 is marked by a cross at the map center and the region synthesized is shown as a circle. Note the velocity gradient in the feature across the position of NRAO150. The 22.5 HPBW is shown inset at the lower left in each panel.

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In the text

Figure 11: Finer-scale hybrid synthesis maps of integrated 12CO brightness. The 5.8 hybrid synthesis profiles are summed over the 5-channel (1.05 ) intervals most closely centered about the velocity indicated at the upper left in each panel and the integrals are scaled by 1/1.05 to reflect mean brightness over a 1 -wide interval. Contours are shown at levels 1, 2, 4, 6 and 8 . The position of NRAO150 is marked by a cross at the map center. The 5.8 synthesized HPBW is shown inset at the lower left in each panel.

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In the text

	Figure 12: Left: same as Fig. 5 but using the 30 m data only. Right: same as right but using the total field-of-view of the 30 m data, i.e. .
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In the text

Figure 13: Moments of the components and -10.5 and together observed at two different resolution. From top to bottom: peak temperature, integrated area, centroid velocity, 2nd order moment (proportional to the FWHM for a Gaussian line) and the modulus of the gradient of centroid velocity (for a flat rotation curve of the Galaxy, corresponds to 2.5 kpc in the direction of NRAO150 and at 2.5 kpc, corresponds to ).

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In the text

	Figure 14: Maps of spectra around the profiles shown in Fig. 4 sorted by distance to NRAO150 from top to bottom. Left: the feature shown around (+3'',-3''), (+10.5'',-10.5'') and (-7.5'',-13.5''). Right: the -10.5 and features shown around (-27'',-27''), -28.5'',+25.5'' and (+36'',-24'').
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In the text