Publications of the Astronomical Society of the Pacific 105: 1127-1140, 1993 October
The Distribution of Interstellar Dust in the Solar Neighborhood
John E. Gaustad Department of Physics and Astronomy, Swarthmore College, Swarthmore, Pennsylvania 19081 Electronic mail: jgaustal @cc.swarthmore.edu Dave Van Buren Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology and Jet Propulsion Laboratory, Pasadena, California 91125 Electronic mail: [email protected] Received 1993 March 24; accepted 1993 July 7
ABSTRACT. We surveyed the IRAS data base at the positions of the 1808 06-B9.5 stars in The Bright Star Catalog for extended objects with excess emission at 60 μιη, indicating the presence of interstellar dust at the location of the star. Within 400 pc the filling factor of the interstellar medium for dust clouds with a density >0.5 cm-3 is 14.6±2.4%. Above a density of 1.0 cm-3, the density distribution function appears to follow a power law of index —1.25. When the dust clouds are mapped onto the galactic plane, the sun appears to be located in a low-density region of the interstellar medium of width about 60 pc extending at least 500 pc in the direction of longitudes 80ο-260ο, a feature we call the "local trough."
1. INTRODUCTION In a previous pilot study (Van Buren 1989), a small ( —0.05 sr) patch of sky in the southern Milky Way was The infrared cirrus observed by IRAS comprises ex- searched for cirrus hotspots around all stars earlier than tended emission on all scales with a wispy or filamentary B5 in the Michigan HD Catalog (Houk and Cowley 1975). structure (Low et al. 1984; Good and Gautier 1986). This While accurate distances to these stars are not yet known, emission is very well correlated with 21 cm column densi- so a reasonable three-dimensional map could not be made, ties (Terebey and Fich 1986). Energetic arguments con- the volume filling factor of the cirrus was determined to be sidering the extinction of starlight and emission observed 0.2 ±0.1 on the basis of the detection of five hotspots. in the IRAS bands lead to the conclusion that the cirrus In this paper we complete the first step of the project dust and the extinguishing dust are the same (Boulanger et suggested by the pilot study, namely a complete survey for al. 1985). If this three-way correspondence is real, then it cirrus hotspots of all stars earlier than type AO in The is clear that the infrared provides a powerful probe for a Bright Star Catalog. Using spectroscopic parallaxes, we de- major component of the interstellar medium. rive the local distribution of interstellar matter, albeit with An important consequence of the correspondence is that large uncertainties in the distance dimension. An accurate not only can the two-dimensional projected-on-the-sky three-dimensional view of the local interstellar medium properties of the interstellar medium be studied on a fine will emerge in the next few years when the HIPPARCOS scale ( ~ 1 arcmin), but now the third dimension can also parallaxes for these stars become available and are com- be probed by considering the stars which power the emis- bined with the present results. We also determine the local sion. A star embedded in the cirrus will heat the dust density distribution function using several simplifying as- nearby, raising the emission in all IRAS bands and increas- sumptions. ing the color temperature. If the dust is dense enough, the Our results disagree with those of the Hopkins group added emission exceeds the sensitivity of the IRAS detec- (Murthy et al. 1992) both in detail and interpretation. We tors and a cirrus "hotspot" appears at the star's position in present our resolution of the differences in Sec. 7. the Infrared Sky Survey Atlas.1 In practice, all stars earlier than AO within 150 parsecs and embedded in gas with hydrogen density greater than about 0.5 cm-3 and a nor- mal gas-to-dust ratio will be detected. If the distance to the 2. CIRRUS HOTSPOTS star is known, a measurement of the infrared flux and an- Cirrus hotspots are regions of the cirrus dust locally gular size of the hotspot gives the ISM density at a partic- heated by an embedded star. Because of the enhanced ra- ular point. In this way, a sparse network of ISM densities diation density, the dust is heated a bit above the equilib- can be obtained and integrated into a three-dimensional rium temperature in the interstellar radiation field. For map. dust with the properties described by Draine and Lee (1984), the color temperature achieved depends on the 1The Infrared Sky Survey Atlas (ISSA) is a data product available from distance from the star as 1 — the Infrared Processing and Analysis Center providing a complete view 1J 97/»α 1/6 τ l/6„—1/3 /ix of the sky in all four IRAS bands at a pixel size of 1.5 arcmin. color ^ ' μτη ^38 ^pc ^ '
H 27 © 1993. Astronomical Society of the Pacific
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1128 GAUSTAD AND VAN BUREN when the star puts most of its bolometric flux out in the Table 1 ultraviolet (Van Buren and McCray 1988). [Note that this Stars Not Included in Survey equation is a revision of Eq. (1) of Van Buren (1989).] 891 928 b 1610 1764 b 1851 Here the typical grain size is αμηι μιη, the stellar bolometric 1880 1886 b 1893 1894 b 1896 (UV) flux is 1038X Ζ,3 erg s_1, and the dust in question is 1897 1932 b 1949 2170 χ 2279 8 2357 2358 b 2783 2790 b 2871 situated rpc parsecs from the star. In the pilot study typical 2948 2980 b 3143 3241 b 3447 dust temperatures were found to be 70 Κ at distances of 3466 3498 χ 3878 3946 χ 4082 order 0.2 pc from the stars with luminosities of order 1038 4116 4119 χ 4135 4729 b 4731 -1 4899 5035 b 5211 5605 b 5833 ergs , implying typical grain sizes of a few tenths of a 5985 6026 b 6113 6185 b 7169 micron. 7594 8143 χ 8209 8215 χ 8356 An expression relating the equivalent gas density in a 8438 8513 χ 8520 8597 χ 8704 hotspot to observed quantities can be obtained fairly sim- χ — No data in IRAS data base ply by noting that the fraction of the stellar bolometric flux b -- Visual companion unresolved by IRAS (i^Boi) emitted in the infrared must equal the fraction ab- sorbed in the ultraviolet, which is in turn equal to the absorption optical depth r (for r
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1129
-14,5 -14,5
-15.0 -15.0
-15,5 -15,5 -15,5
-16,0 -16,0 6.80 6.75 6.80 6,75 6.80 6.75 RA (Hours] RA (Hours] RA (Hours] HR 2522 6Û-1Û0 excess ,ί} \ -¾ 'S 4i7
-15,5 -15,5" 0 20 Rodius from position (arcmin) 6.80 6,75 6.80 6,75 RA (Hours] RA (Hours]
Fig. Í—IRAS BigMap images of the cirrus hotspot around HR 2522. The bottom center panel is a 60-100 μπι excess map constructed as described in the text. The bottom right panel shows the average surface brightness of the 60 μπι image (heavy line) and of the excess map (light line, arbitrary units) as a function of angular distance from the position of the star. the intensities at the two wavelengths were identical when interactively mask out anomalously bright or dark regions averaged over the entire image. Regions heated above the in either the object circle or the background annulus. It ambient temperature have excess intensity at 60 μπι com- then calculates the flux from the object by integrating the pared to cooler regions, and so show up as bright on such intensity over the chosen radius, subtracting out the back- an excess map. We used this differencing procedure for a ground level averaged over the outer annulus and taking temperature indicator rather than calculating a color tem- correct account of masked regions. Once the radii of the perature from the intensity ratio at each point because of object and background annuli are chosen at 60 μπι, the concern over zero-point offsets in the intensity scale. The same radii are used for measuring the flux at the other lower central panel of Fig. 1 shows an example of such an three wavelengths. excess map. At least three persons measured each object. If the re- For each wavelength the program first displays a 60 μιη sults differed by more than the statistical errors, the mea- image of the region surrounding the star, with an overlaid surers conferred about their size determination and mask- contour map. It also computes and displays the average ing procedures, and the images were remeastired. A final intensity as a function of radius from the stellar position, as conference, including examination of the appearance of the well as the similar quantity for the excess map (see the images, resulted in a judgement as to whether a heated dust lower right panel of Fig. 1 ). The user examines both the cloud had truly been detected. Finally, all acceptable mea- image and the intensity plots to determine the radius of the surements of radius and fluxes were averaged. object, taken to be the distance from the star at which the We are not very sensitive to systematic errors in the intensity or excess intensity reaches background level. Pri- density determinations arising from the interactively cho- mary weight is given to the excess intensity in the radius sen sizes of hotspots. To see this, consider the case of a determination, although in some cases, where this function smooth medium surrounding a star to large distances. As is noisy, the 60 μπι intensity is also used. The user also long as a reasonable background is chosen, a smaller cho- chooses the inner and outer radii of a background annulus sen size will encompass a smaller flux, yielding a density surrounding the object. (The object circle and background estimate similar to a larger size and larger flux. In both annulus chosen for the sample star are marked in the pan- cases the integrated flux per path length, which is propor- els of Fig. 1.) The program provides the opportunity to tional to the density, is similar.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1130 GAUSTAD AND VAN BUREN
Table 2 contains the measured angular radii and fluxes is advised to examine the actual images on the ISSA sur- for the 302 objects which were detected. The formal errors vey.) Of the 1808 06-B9.5 stars in The Bright Star Cata- in the angular radii are typically 1 arcmin ( 1 pixel), and in log, 1451 stars, those not listed in either Table 1 or Table 2, the fluxes about 20%, but these may be as high as 100% in were judged not to show excess 60 μιη radiation, by exam- some instances where the background has rich structure. ination either of the AddScan trace or of the BigMap im- (Anyone using this data for other than statistical purposes age. The nondetections could be interpreted to give up- Table 2 Data for Hotspots
Type 1 b d hi hs f60 fioo Fir/FBoI θ R η T25/60 Τ601100 (deg) (deg) (pc) (Jy) (Jy) (Jy) (Jy) (arcmin) (pc) (cm ^) (K) (K) 38 B2V 6.73 11455 -24.55 620 0.44 0.45 1.40 1.80 0.000310 10.0 0.15 61 35 70 26 And B8V 6.11 116.70 -18.68 180 -0.08 0.23 2.10 2.50 0.000430 6.0 1.30 51 35 91 B5IV 5.57 118.68 -10.63 260 3.40 3.50 53.00 130.00 0.006700 20.0 1.5 3.90 47 28 96 B9IV 5.74 118.92 -9.62 160 0.33 0.44 1.80 6.90 0.000910 4.0 0.2 4.50 58 25 113 B9 mn 5.94 120.29 -2.79 200 0.56 0.02 7.70 9.50 0.001400 6.0 0.3 3.80 32 35 121 13 Cas B6V 6.18 120.94 3.73 250 0.45 0.61 2.20 5.50 0.000770 4.0 0.3 2.40 59 28 155 53 Psc B2.5IV 5.89 117.70 -47.49 490 0.49 0.24 3.60 5.90 0.000320 7.5 1.1 0.27 47 32 189 B5V 5.67 121.72 -14.99 210 1.40 1.80 13.00 27.00 0.001700 10.0 0.6 2.50 53 29 193 22 o Cas Β5ΙΠε 4.54 121.78 -14.57 200 0.77 0.68 3.90 6.20 0.000140 10.0 0.6 0.21 54 32 208 23 Cas Β8ΙΠ 5.41 122.69 11.98 200 7.60 7.80 35.00 110.00 0.009700 14.0 0.8 11.00 57 26 241 B9.5V 6.21 122.95 -11.30 140 1.50 2.00 15.00 20.00 0.007600 5.0 0.2 34.00 52 34 477 53t And Β8ΙΠ 4.94 132.92 -21.34 160 0.74 0.94 4.50 6.90 0.000620 7.0 0.3 1.70 57 32 482 Β8ΙΠ 6.71 129.52 -3.59 340 1.30 1.20 5.20 11.00 0.002400 6.0 0.6 3.60 57 29 533 1 Per B1.5V 5.52 131.57 -6.70 470 4.20 15.00 81.00 150.00 0.003400 13.0 1.8 1.70 56 30 548 46 ω Cas B8ffl 4.99 128.77 6.55 170 8.90 12.00 57.00 210.00 0.011000 16.0 0.8 12.00 57 25 561 Β5ΙΠ 6.02 130.80 -0.14 380 1.90 3.10 11.00 31.00 0.002500 10.0 1.1 2.00 60 27 604 57 And B8 V+A0 V 4.84 136.97 -18.56 84 52.00 20.00 2.80 2.00 0.001300 5.0 0.1 9.40 146 44 801 35 Ari B3 V 4.66 151.29 -28.93 170 1.60 2.80 15.00 11.00 0.000380 9.0 0.5 0.76 56 42 811 89 π Cet B7V 4.25 191.81 -60.57 96 1.10 1.80 11.00 17.00 0.000620 8.0 0.2 2.50 54 32 873 21 Per B9pSi 5.11 151.88 -23.77 87 0.23 0.15 1.90 4.20 0.000230 6.0 0.1 1.40 48 29 890 B7V 5.28 142.11 -5.63 140 8.90 6.30 69.00 110.00 0.005800 13.0 0.5 10.00 49 32 938 53 Ari Β 1.5 V 6.11 162.98 -34.21 570 0.80 0.50 7.50 14.00 0.000360 7.0 1.2 0.28 47 30 944 55 Ari B8m 5.72 156.01 -24.78 180 1.30 1.40 6.10 17.00 0.001200 10.0 0.5 2.10 57 27 950 B4V 6.15 148.87 -13.30 290 0.29 0.37 4.50 12.00 0.000610 8.0 0.7 0.83 49 27 985 B2.5 Ven 4.84 137.46 7.06 220 4.10 6.10 29.00 130.00 0.001400 14.0 57 24 987 29 Per B3 V 5.15 145.60 -6.06 190 0.65 0.16 4.20 3.50 0.000087 6.0 44 41 1011 B5V 5.29 146.78 -6.50 170 0.51 0.31 2.50 10.00 0.000210 6.0 0.3 0.66 52 24 1034 B5V 4.98 147.52 -6.19 150 0.38 0.02 2.20 4.60 0.000100 5.0 0.2 0.41 37 29 1035 B9Ia 4.21 141.50 2.88 1000 10.00 15.00 120.00 320.00 0.003700 16.0 4.8 0.69 52 27 1074 B1 V 5.90 156.32 -16.75 590 -3.20 18.00 44.00 47.00 0.001200 17.0 2.9 0.37 64 37 1079 6 Tau B9IV 5.77 175.51 -36.55 160 1.00 1.00 3.20 15.00 0.001500 7.0 0.3 4.00 60 24 1092 B8V 5.83 282.23 -43.68 150 0.26 0.01 1.50 4.60 0.000340 5.0 0.2 1.40 36 26 1122 39 Ô Per Β5ΠΙ 3.01 150.28 -5.77 110 21.00 29.00 360.00 860.00 0.004400 40.0 1.3 3.20 49 28 1123 40 Per B0.5V 4.97 158.92 -16.70 400 -5.40 -1.80 260.00 260.00 0.001300 31.0 3.6 0.34 38 1142 17 Tau B6ffle 3.70 166.18 -23.85 130 52.00 80.00 430.00 600.00 0.011000 8.0 0.3 34.00 56 33 1144 18 Tau B8V 5.64 165.70 -23.26 140 1.70 0.85 21.00 49.00 0.003600 8.0 0.3 10.00 44 28 1149 20 Tau B8m 3.87 166.17 -23.51 98 86.00 98.00 720.00 1000.00 0.030000 12.0 0.3 79.00 53 33 1151 21 Tau BSV 5.76 166.05 -23.36 140 9.20 4.60 77.00 110.00 0.011000 5.0 0.2 50.00 46 33 1163 B2.5V 6.57 160.08 -16.25 360 0.35 1.10 2.90 6.70 0.000310 8.0 0.8 0.33 63 28 1165 25 η Tau B7me 2.87 166.67 -23.45 75 23.00 19.00 150.00 170.00 0.001300 9.0 0.2 5.80 52 36 1174 30 Tau B3 V+F5V 5.07 177.17 -32.53 210 0.90 2.50 25.00 30.00 0.000770 11.7 0.7 0.99 50 35 1185 B8m 6.07 168.50 -24.44 250 0.38 1.20 1.50 5.50 0.000880 5.0 0.4 2.20 73 25 1191 B1 V 5.77 160.23 -15.14 510 2.60 5.90 27.00 50.00 0.000800 11.0 1.6 0.44 57 30 1199 31 Tau B5V 5.67 182.07 -34.88 170 0.33 2.50 12.00 21.00 0.000820 12.0 0.6 1.30 57 31 1215 B1.5V 5.49 160.47 -13.97 380 0.77 0.90 12.00 19.00 0.000300 7.0 0.8 0.34 48 32 1239 35 λ Tau B3 V+A4IV 3.47 178.37 -29.38 97 5.70 -8.00 34.00 74.00 0.000180 16.0 0.5 0.35 29 1243 B5V 5.67 180.76 -30.80 180 0.96 1.50 7.40 25.00 0.000860 7.0 0.4 2.20 56 25 1244 35 Eri B5V 5.28 191.88 -37.81 190 0.64 1.30 6.70 20.00 0.000780 7.0 0.4 1.80 56 26 1258 B2.5V 6.46 214.57 -45.74 490 0.25 -0.15 2.50 3.40 0.000220 11.0 1.6 0.12 34 1268 41 Tau B9pSi 5.20 167.43 -17.96 110 1.40 1.30 2.00 4.40 0.000580 6.0 0.2 2.80 70 29 1307 B8Vn 6.23 182.69 -28.42 150 12.00 25.00 120.00 220.00 0.034000 10.0 0.5 67.00 56 31 1328 B9V 6.22 158.72 -5.93 160 0.93 0.50 3.20 8.20 0.001500 5.0 0.2 5.90 54 27 1333 Β 1.5 IV 5.55 152.80 0.57 490 17.00 77.00 540.00 690.00 0.020000 24.0 3.4 5.20 53 35 1350 53 Per B4IV 4.85 156.08 -2.40 200 2.10 2.70 15.00 39.00 0.000870 9.0 0.5 1.50 55 27 1377 55 Per B8V 5.73 165.38 -10.65 140 0.62 0.50 2.70 7.70 0.000600 6.0 0.2 2.20 55 27 1399 72 Tau B7V 5.53 174.31 -17.69 160 55.00 110.00 280.00 860.00 0.075000 38.0 1.8 37.00 63 26 1415 B3 V 5.55 193.42 -30.57 250 1.00 2.30 15.00 15.00 0.000740 11.7 0.8 0.80 54 38 1443 δ Cae B2IV-V 5.07 250.37 -43.22 410 0.19 1.20 13.00 12.00 0.000480 14.7 1.8 0.24 50 38 1445 B9pHg 5.88 170.77 -12.53 130 0.51 0.30 1.70 -0.60 0.000300 5.0 0.2 1.40 55 1471 B8V 5.92 177.88 -17.22 150 0.51 0.32 3.20 11.00 0.000860 4.0 0.2 4.30 50 25 1512 Β5ΙΠ 6.35 176.62 -14.03 390 0.30 0.68 4.80 7.70 0.000700 8.0 0.9 0.70 53 32 1520 57 μ Eri B5IV 4.02 200.53 -29.34 130 0.70 0.90 1.40 0.40 0.000095 7.0 71 79 1553 B5V 6.11 189.03 -21.00 200 0.26 2.90 2.50 7.90 0.000550 8.0 26 1555 5 Cam B9.5V 5.52 153.07 7.36 96 0.40 1.50 5.10 11.00 0.001500 7.7 0.2 6.20 29 1600 B7V 6.09 186.12 -16.94 170 0.60 -1.10 17.00 26.00 0.001900 11.0 0.6 3.10 33 1622 11 Cam B2.5 Ve 5.08 150.99 10.80 230 9.70 6.00 47.00 100.00 0.001200 13.0 0.9 1.30 52 29 1640 B2.5IV 6.41 214.33 -30.21 650 1.20 1.40 22.00 57.00 0.004700 13.0 2.5 1.70 47 27 1659 103 Tau B2V 5.50 179.25 -9.56 270 -0.80 2.70 19.00 13.00 0.000280 15.0 53 46 1660 105 Tau B2 Ve 5.89 181.34 -11.09 270 16.00 9.70 140.00 370.00 0.003400 20.3 1.6 1.90 47 27 1669 Β2Π+Κ3 6.02 168.95 -1.49 350 9.00 6.00 28.00 58.00 0.000270 6.0 0.6 0.41 56 29 1679 69 λ Eri B2 IVne 4.27 209.14 -26.69 280 -1.70 1.10 21.00 -33.00 0.000016 24.0 2.0 0.00 46 1705 4 κ Lep B9V 4.36 213.88 -27.55 70 0.80 0.70 6.80 19.00 0.000620 9.0 0.2 3.00 50 27 1712 09.5 Ve: 5.96 172.08 -2.26 580 120.00 440.00 2200.00 2600.00 0.017000 20.0 3.4 4.40 56 36 1713 19 β Ori B8 lae: 0.12 209.24 -25.25 280 50.00 13.00 10.00 12.00 0.000029 10.0 0.8 0.03 81 35 1719 15 Cam B5V 6.13 152.71 11.75 230 1.10 1.90 13.00 28.00 0.002000 9.0 0.6 3.00 53 29 1731 B3IV 6.56 218.64 -28.40 580 -0.50 0.17 3.80 9.00 0.000550 11.0 45 28
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1131
Table 2 (Continued) cu Type ι b d fl2 f25 fóo fioo F IR/FBoI θ R η T25/6O ^601100 (cleg) (deg) (pc) (Jy) (Jy) (Jy) (Jy) (arcmin) (pc) (cm"3) (Κ) (K) 1735 20 τ Ori B5 III 3.60 208.28 -23.96 140 2.30 1.10 8.60 8.20 0.000120 14.3 0.6 0.18 52 39 1749 20 ρ Aur B3 V 5.23 166.56 2.93 230 0.50 0.65 4.50 13.00 0.000270 5.5 0.4 0.68 53 27 1750 B9IV 6.33 177.88 -5.08 180 2.40 3.60 7.30 31.00 0.006500 8.0 0.4 14.00 67 24 1753 B3 V 6.36 220.34 -28.36 390 0.90 0.31 1.40 2.50 0.000180 6.0 0.7 0.24 56 31 1759 B8 III 6.39 207.19 -22.66 300 1.20 2.30 7.80 25.00 0.004400 5.0 0.4 9.20 60 26 1763 B1 V 5.80 194.62 -15.61 620 44.00 200.00 1700.00 3000.00 0.057000 22.0 4.0 13.00 52 31 1798 113 Tau B2 Vn 6.25 188.00 -10.32 460 1.40 5.50 18.00 26.00 0.001500 7.7 1.0 1.30 61 33 1808 115 Tau B5V 5.42 187.07 -9.42 190 2.20 6.30 15.00 38.00 0.002000 10.7 0.6 3.20 65 27 1810 114 Tau B2.5 IV 4.88 183.75 -7.17 310 2.20 -1.00 88.00 93.00 0.002400 22.0 2.0 1.10 37 1847 B7ine 5.46 188.50 -8.88 230 1.40 3.50 17.00 39.00 0.002200 9.0 0.6 3.30 56 29 1855 36 ν Ori B0V 4.62 210.44 -20.98 530 0.49 4.30 5.00 0.40 0.000070 4.5 0.7 0.09 75 1858 120 Tau B2 IV-Ve 5.69 187.39 -7.84 410 4.80 12.00 70.00 140.00 0.004000 15.0 1.8 2.00 55 30 1861 B1IV 5.35 205.14 -18.20 690 1.10 32.00 170.00 97.00 0.006300 17.0 3.4 1.70 55 50 1868 B1 V 5.34 204.84 -17.81 540 6.70 26.00 130.00 190.00 0.003600 11.0 1.7 1.90 56 33 1875 121 Tau B2.5 IV 5.38 182.95 -4.52 360 2.80 23.00 34.00 71.00 0.003200 18.0 1.9 1.60 71 29 1876 37 φΐ Ori B0ΙΠ 4.41 195.40 -12.29 670 1.90 30.00 310.00 370.00 0.002100 14.0 2.7 0.70 50 35 1895 41 θ1 Ori 06 5.13 209.01 -19.38 790 12000.00 61000.00 48000.00 32000.00 0.340000 15.0 3.5 87.00 82 45 1928 125 Tau B3IV 5.18 181.90 -2.71 300 0.82 4.50 16.00 12.00 0.001000 9.0 0.8 1.20 60 44 1931 48 σ Ori 09.5 V 3.81 206.82 -17.34 410 7.60 84.00 290.00 150.00 0.000950 10.0 1.2 0.71 60 52 1934 47 ω Ori B3 lile 4.57 200.73 -14.03 290 7.00 18.00 170.00 270.00 0.005300 19.0 1.6 3.00 51 32 1944 B7V 6.38 221.62 -23.71 250 1.10 0.17 1.30 1.70 0.000350 9.0 0.7 0.48 52 34 1945 B8IV 6.43 179.04 -0.50 250 0.85 2.00 10.00 27.00 0.005800 4.0 0.3 18.00 56 27 1946 B3IV 4.86 190.09 -7.31 260 -0.15 3.20 3.90 4.70 0.000240 8.0 0.6 0.37 74 35 1962 B3 IVp 6.21 220.74 -22.74 480 0.06 0.34 1.10 1.90 0.000210 5.0 0.7 0.27 61 31 1993 B2IV-V 5.29 193.17 -7.33 440 1.60 5.50 15.00 39.00 0.001300 10.0 1.3 0.91 63 27 1997 B9 Vn 6.07 187.23 -3.64 150 1.10 0.72 2.00 7.20 0.001100 5.0 0.2 4.70 62 25 2058 Β 1.5 V 6.57 210.05 -14.50 770 0.29 2.40 16.00 28.00 0.001600 7.0 1.6 0.91 53 31 2111 B9 lab 6.05 182.90 2.23 2100 0.70 -0.40 3.60 10.00 0.000650 7.0 4.3 0.14 27 2142 B2 Ven 5.21 213.60 -13.54 280 3.50 8.90 32.00 12.00 0.000860 8.5 0.7 1.10 60 64 2154 B5IV 5.38 211.57 -11.87 250 -0.45 0.17 2.30 6.00 0.000120 6.0 0.4 0.25 48 27 2159 B3V 4.42 194.81 -2.72 160 2.00 2.30 10.00 24.00 0.000360 5.0 0.2 1.40 57 28 2213 Β3ΙΠ 6.52 224.88 -16.35 770 0.70 0.78 1.10 4.70 0.000890 5.0 1.1 0.72 72 24 2266 B2V 5.52 227.52 -16.05 380 0.42 0.65 2.00 2.30 0.000140 4.7 0.5 0.24 61 36 2276 B5III 6.54 199.00 -1.32 530 1.80 3.10 15.00 39.00 0.005500 10.0 1.5 3.20 57 27 2309 B5 Ve 6.12 221.58 -11.80 250 0.72 0.20 3.30 11.00 0.000540 7.5 0.5 0.90 47 25 2344 10 Mon B2V 5.06 214.52 -7.39 300 -1.70 -3.50 19.00 45.00 0.000410 20.0 1.8 0.21 28 2420 52 ψ3 Aur B8III 5.20 175.32 14.77 180 1.20 3.80 8.00 14.00 0.001600 11.0 0.6 2.40 66 31 2442 09.5 III 6.21 210.03 -2.11 1200 1.10 22.00 220.00 240.00 0.002600 11.3 4.0 0.57 50 36 2451 ν Pup B8III 3.17 251.94 -20.54 75 1.50 0.51 1.50 3.60 0.000038 6.0 0.1 0.26 61 28 2467 06e 6.37 206.21 0.80 1500 9.70 83.00 740.00 950.00 0.006900 27.3 12.0 0.51 51 34 2490 42 Cam B4IV 5.14 147.80 24.88 280 0.50 0.48 1.80 2.00 0.000130 7.0 0.6 0.20 59 36 2522 B6V 5.39 226.21 -7.38 170 4.40 5.70 48.00 92.00 0.005500 12.0 0.6 8.30 52 30 2538 13 κ CMa Β 1.5 IVne 3.96 242.36 -14.49 320 11.00 8.30 54.00 130.00 0.000960 23.0 2.1 0.41 53 28 25% 20 ι CMa Β3Π 4.37 228.70 -6.68 390 2.80 2.50 25.00 45.00 0.000550 11.0 1.3 0.39 50 31 2627 Bllb 6.49 222.17 -2.15 1600 3.60 2.60 27.00 58.00 0.001700 4.0 1.9 0.79 50 29 2653 24 o2 CMa B3 lab 3.02 235.55 -8.23 680 2.60 1.10 3.90 17.00 0.000064 8.0 1.6 0.04 59 24 2657 23 γ CMa Β8Π 4.12 228.25 -4.41 320 1.20 0.71 5.10 11.00 0.000260 6.0 0.6 0.41 52 29 2678 B0.5IV 5.39 224.71 -1.79 580 52.00 140.00 870.00 1900.00 0.018000 18.0 3.0 5.30 54 29 2702 B2IV-V 4.83 250.69 -13.83 360 1.70 2.10 20.00 49.00 0.000920 12.0 1.3 0.65 51 28 2734 B0.5V 6.12 239.81 -7.65 920 3.80 4.70 27.00 110.00 0.002100 15.0 4.0 0.47 55 25 2749 28 ω CMa B2 IV-Ve 3.85 239.41 -7.15 230 4.80 2.40 13.00 46.00 0.000250 11.0 0.7 0.31 55 25 2769 B4V 5.80 250.08 -11.91 260 2.20 2.30 19.00 61.00 0.002600 11.0 0.8 2.90 52 26 2770 B2IV-V 5.03 248.52 -11.12 390 -0.30 0.34 2.90 6.20 0.000092 6.0 0.7 0.12 52 29 2782 09 lb 4.40 238.18 -5.54 1100 -9.30 0.59 160.00 150.00 0.000420 19.0 5.8 0.07 34 39 2787 B2 V+B3 IVne 4.66 248.78 -10.91 230 5.60 7.40 53.00 66.00 0.000980 15.0 1.0 0.88 53 35 2812 B7IV 4.96 233.29 -2.06 140 5.10 5.80 45.00 96.00 0.003600 11.0 0.5 7.30 52 29 2829 B7III 6.31 248.48 -9.49 400 0.06 -0.25 1.10 4.10 0.000320 5.0 0.6 0.50 25 2897 B1 V 6.21 230.45 2.52 660 -0.80 0.25 4.80 -3.80 -0.000007 8.0 1.5 0.00 46 2907 B8pSi 6.26 253.13 -9.78 200 2.00 5.30 24.00 87.00 0.014000 9.0 0.5 24.00 57 25 2911 B3 Vne 5.54 249.85 -7.95 230 4.40 5.50 31.00 63.00 0.001900 13.0 0.9 2.00 55 29 2954 B2IV-V 5.80 250.46 -7.16 550 -0.22 -0.72 14.00 13.00 0.000740 8.0 1.3 0.52 40 3020 B6IV 6.03 257.51 -9.53 270 0.17 0.25 1.80 2.50 0.000320 4.0 0.3 0.93 53 33 3023 B2IV-V 5.90 239.19 1.34 600 -0.03 0.68 1.90 6.60 0.000280 5.0 0.9 0.28 63 25 3078 B2IV 6.04 257.32 -8.10 630 1.60 0.88 3.90 13.00 0.000570 9.0 1.7 0.31 57 25 3088 B1.5IV 5.70 267.62 -13.54 630 -0.85 1.80 10.00 -0.88 0.000290 11.0 2.0 0.13 55 3091 B2V 5.49 251.48 -4.14 380 0.40 0.37 4.20 8.30 0.000180 6.0 0.7 0.24 49 30 3129 B1 Vp+B3 IV: 4.41 263.48 -10.28 350 -0.71 7.70 48.00 53.00 ,0.000410 13.0 1.3 0.28 54 36 3142 B2IV-V 6.32 264.20 -10.51 580 1.10 3.50 43.00 100.00 0.004300 12.0 2.0 1.90 49 28 3147 B2 IVpne 5.81 273.93 -15.80 500 2.60 1.90 12.00 24.00 0.000830 15.0 2.2 0.34 54 29 3157 B2IV-V 6.10 268.39 -12.48 540 0.91 0.96 6.20 6.00 0.000590 8.0 1.2 0.42 54 38 3159 B3V 4.82 276.55 -16.92 190 -0.04 0.39 1.60 -2.20 0.000019 6.0 0.3 0.05 58 3217 B6 Ve 6.28 277.20 -16.24 240 -0.27 -0.17 2.00 4.40 0.000180 8.0 0.6 0.29 29 3223 ε Vol B6IV 4.35 281.62 -18.56 ,130 1.20 0.87 6.20 15.00 0.000250 9.0 0.3 0.66 53 28 3244 B2.5 IV 5.13 262.88 -6.92 340 0.49 1.30 5.50 7.10 0.000330 7.0 0.7 0.43 58 34 3415 B3 V+B3 Vn 5.26 274.14 -10.52 230 1.10 1.50 13.00 15.00 0.000560 11.0 0.7 0.69 52 36
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1132 GAUSTAD AND VAN BUREN
Table 2 (Continued)
HR Name Type VI b d fi2 f25 ^60 flOO F 1R/Fbo1 θ R η T25/6O Teo/lOO (deg) (deg) (pc) (Jy) (Jy) (Jy) (Jy) (arcmin) (pc) (cm'3) (Κ) (K) 3454 7 η Hya B3V 4.30 223.25 26.32 160 0.38 1.10 3.40 3.10 0.000088 6.0 0.3 0.28 61 39 3494 B3Ia 5.46 265.33 -1.69 1700 3.80 5.00 19.00 48.00 0.001200 4.0 1.9 0.58 59 28 3525 Β1-2ΙΠ 6.00 262.80 1.25 870 -6.00 55.00 520.00 200.00 0.025000 21.0 5.3 4.20 51 63 3527 Born 5.10 266.25 -1.54 990 3.60 17.00 150.00 200.00 0.002500 10.0 2.9 0.78 51 34 3536 B8m 5.59 275.00 -8.43 230 0.44 0.56 2.10 9.20 0.000840 5.0 0.3 2.30 59 24 3574 B5V 4.69 271.62 -4.79 140 2.50 4.20 5.50 22.00 0.000720 8.0 0.3 2.10 73 24 3582 B2IV-V 4.92 276.70 -8.90 380 0.67 0.94 5.00 4.40 0.000240 7.0 0.8 0.28 56 40 3642 B2 IVe 4.71 286.19 -15.43 330 0.78 0.97 8.70 9.20 0.000270 9.0 0.9 0.28 51 37 3654 B5Ia 5.00 267.36 2.25 1600 1.80 1.30 22.00 24.00 0.000700 12.0 5.7 0.11 46 37 3659 B2IV-V 3.44 277.69 -7.37 190 -0.26 1.30 23.00 28.00 0.000180 13.0 0.7 0.22 47 35 3663 Β3ΠΙ 3.97 280.22 -9.61 240 1.40 5.40 99.00 190.00 0.002100 21.0 1.5 1.30 46 30 3860 ζ Cha B5V 5.11 295.57 -21.04 170 0.27 1.00 6.90 6.40 0.000410 8.0 0.4 0.93 53 39 3886 B2.5IV 5.55 271.85 6.67 440 -0.80 0.70 12.00 19.00 0.000660 12.0 1.5 0.39 47 32 3925 B3V 5.71 273.25 7.14 270 -0.85 1.10 15.00 28.00 0.000680 12.0 0.9 0.65 48 30 3943 B3 V 6.05 275.67 5.04 330 2.20 2.30 17.00 40.00 0.002100 8.0 0.8 2.50 53 28 3971 B7IVne 6.14 284.49 -5.18 240 0.36 0.42 2.60 5.60 0.000670 4.0 0.3 2.20 54 29 4037 B8me 3.32 290.16 -11.18 77 3.60 1.80 3.10 2.30 0.000078 8.0 0.2 0.39 68 43 4140 B4 Vne 3.32 287.18 -3.15 78 38.00 51.00 510.00 970.00 0.004800 5.0 0.1 38.00 50 30 4329 B2V 5.57 294.51 -9.74 330 0.43 0.32 2.00 7.10 0.000086 5.0 0.5 0.17 54 25 4355 B8V 5.23 292.44 -3.33 110 0.44 -0.71 0.81 98.00 0.002200 8.0 0.3 7.40 13 4387 B9.5-A0 V 6.27 297.03 -13.33 150 1.00 1.60 4.80 21.00 0.005200 7.0 0.3 16.00 61 24 4390 B5Vn 3.89 289.96 6.09 98 0.44 0.47 1.20 0.29 0.000048 5.0 0.1 0.30 64 96 4401 B5V 5.11 293.78 -3.66 160 0.46 0.68 20.00 70.00 0.001400 4.0 0.2 6.80 43 25 4549 B4V 4.90 296.73 -3.05 170 -0.68 -0.03 6.50 13.00 0,000140 4.0 0.2 0.67 30 4552 ß Hya B9 IllpSi 4.28 289.27 27.41 110 0.99 0.83 1.40 2.40 0.000150 5.0 0.1 0.84 68 31 4583 ε Cha B9Vn 4.91 300.21 -15.62 85 19.00 17.00 13.00 14.00 0.003000 4.0 0.1 27.00 81 37 4620 B9V 5.34 295.62 13.57 97 0.44 0.19 1.80 6.20 0.000350 5.0 0.1 2.20 51 25 4621 B2 IVne 2.60 296.00 11.57 120 19.00 19.00 76.00 110.00 0.000300 18.0 0.6 0.42 58 33 4625 B3IVe 5.48 294.39 20.93 310 1.50 0.34 14.00 22.00 0.000750 11.0 1.0 0.67 41 32 4692 B9V 6.21 299.77 -3.16 150 4.90 1.90 17.00 63.00 0.008400 9.0 0.4 19.00 51 25 4732 B3 Vn 4.82 298.98 11.23 190 -1.90 1.80 16.00 -56.00 -0.000170 18.0 1.0 -0.16 51 4743 σ Cen B2V 3.91 299.10 12.47 180 1.90 0.70 11.00 13.00 0.000089 14.0 0.8 0.11 47 36 4798 α Mus B2IV-V 2.69 301.66 -6.30 140 12.00 39.00 160.00 280.00 0.001100 25.0 1.0 0.96 58 31 4844 β Mus B2.5V 3.05 302.45 -5.24 100 4.50 21.00 73.00 110.00 0.000470 15.0 0.5 0.94 60 33 4848 B3V 4.65 302.23 6.38 180 -0.11 2.80 11.00 25.00 0.000320 8.0 0.4 0.69 29 4853 β Cru B0.5 ΙΠ 1.25 302.46 3.18 150 130.00 370.00 1100.00 1500.00 0.001200 36.0 1.6 0.69 34 4898 μ1 Cru B2IV-V 4.03 303.36 5.69 250 -2.00 3.10 15.00 36.00 0.000200 9.0 0.7 0.28 57 28 4913 B8-9V 5.16 303.83 11.66 100 0.24 0.48 5.40 15.00 0.000850 7.0 0.2 3.70 50 27 5026 B6V 5.48 307.41 9.87 190 0.50 0.28 2.60 10.00 0.000390 5.0 0.3 1.30 51 25 5027 B0.5 lae 6.02 307.08 6.83 1500 2.80 31.00 230.00 460.00 0.004400 14.0 6.2 0.64 53 30 5030 B6V 6.05 305.37 -9.42 180 1.50 0.33 3.90 15.00 0.000510 7.0 0.4 1.30 49 25 5103 Β8ΙΠ 6.33 310.29 13.98 300 -0.16 0.24 0.94 -3.60 -0.000130 8.0 0.7 -0.16 59 5151 B0.5 III 6.00 309.98 5.40 1100 -1.70 0.66 23.00 37.00 0.000610 11.0 3.6 0.15 42 32 5190 ν Cen B2IV 3.41 314.41 19.89 200 -0.63 3.10 18.00 35.00 0.000190 16.0 0.9 0.18 55 30 5193 μ Cen B2 IV-Ve 3.04 314.24 19.12 160 2.00 2.90 12.00 7.80 0.000100 13.0 0.6 0.16 58 46 5250 47 Hya B8 VpShell 5.15 321.66 35.45 120 0.30 1.10 5.00 5.40 0.000640 5.0 0.2 3.40 57 37 5336 B4V 5.06 306.93 -17.95 180 7.20 9.50 100.00 210.00 0.004900 13.0 0.7 6.70 50 29 5375 Β1ΙΠ 6.09 318.20 11.83 1100 -0.85 5.40 45.00 50.00 0.002600 15.0 4.9 0.48 52 36 5395 τ1 Lup B2IV 4.56 319.92 14.50 310 6.00 11.00 87.00 130.00 0.002400 20.0 1.8 1.20 52 32 5425 σ Lup Β2ΙΠ 4.42 318.93 9.25 400 1.70 7.30 34.00 71.00 0.001100 12.0 1.4 0.68 57 29 5484 4 Lib B9 5.73 332.75 31.32 120 0.84 1.20 1.50 0.89 0.000960 10.0 0.3 2.60 74 49 5628 Β8-9ΠΙ 6.01 313.03 -12.73 220 0.52 0.53 5.10 15.00 0.001700 7.0 0.5 3.50 51 26 5685 27 β Lib B8V 2.61 352.02 39.23 37 1.80 -0.34 3.20 -3.10 0.000008 9.0 0.1 0.08 5778 4 θ CrB B6 Vnne 4.14 49.69 54.71 100 0.23 1.50 4.60 6.40 0.000180 16.0 0.5 0.35 61 33 5780 B6IV 5.17 356.08 36.36 190 0.62 0.54 2.40 2.70 0.000170 7.7 0.4 0.36 57 36 5863 25 Ser B8m 5.40 5.53 38.99 190 1.50 3.40 7.90 15.00 0.001800 9.7 0.5 3.00 65 30 5883 5 χ Lup B9IV 3.95 340.57 15.82 67 3.10 1.50 10.00 34.00 0.000610 9.0 53 26 5902 45 λ Lib B2.5V 5.03 350.72 25.38 200 4.50 14.00 52.00 63.00 0.001300 22.0 59 35 5904 2 Seo B2.5 Vn 4.59 346.88 21.61 180 1.10 17.00 71.00 55.00 0.001100 9.0 0.5 2.00 58 42 5918 B6V 6.03 337.19 10.42 160 0.40 -0.11 3.90 3.90 0.000220 6.0 0.3 0.70 38 5941 48 Lib Β5ΙΠρβ 4.88 356.39 28.63 250 1.20 9.20 40.00 49.00 0.002200 16.0 1.1 1.70 58 35 5944 6 π Seo B1 V+B2V 2.89 347.22 20.23 180 30.00 310.00 1000.00 530.00 0.002600 23.0 1.2 2.00 61 52 5988 B8p 5.92 350.35 20.85 160 -0.87 0.22 5.30 12.00 0.000670 8.0 0.4 1.60 44 29 5993 9 ω ^ Seo B1 V 3.96 352.75 22.77 240 11.00 27.00 93.00 190.00 0.000660 10.0 0.7 0.87 60 29 6002 11 Seo B9.5 Vnn 5.78 359.41 27.93 . 110 0.68 -1.00 8.30 12.00 0.001500 8.0 0.3 5.30 33 6027 14 ν Seo B3V 4.01 354.61 22.70 100 180.00 320.00 1300.00 2500.00 0.015000 43.0 1.2 11.00 58 30 6028 13 Seo B2V 4.59 348.12 16.84 240 5.20 23.00 420.00 480.00 0.006000 19.0 1.3 4.10 46 36 6084 20 σ Seo B2 III+09.5 V 2.89 351.31 17.00 130 2300.00 8000.00 66000.00 110000.00 0.170000 76.0 2.8 55.00 52 32 6096 B9V 6.23 11.79 31.41 130 -0.08 0.05 1.40 4.70 0.000410 6.5 0.2 1.50 43 26 6143 B2ΙΠ-IV 4.23 345.94 9.22 350 1.20 13.00 45.00 93.00 0.001100 17.0 1.7 0.56 60 29 6165 23 τ Seo B0V 2.82 351.54 12.81 230 490.00 950.00 9000.00 20000.00 0.017000 75.0 5.0 3.00 51 29 6168 35 σ Her B9V 4.20 66.91 42.70 57 0.87 -0.01 1.90 1.80 0.000071 7.0 0.1 0.55 39 6211 B8V 6.46 349.63 9.01 210 -0.01 0.24 3.40 6.10 0.001200 4.0 0.2 4.40 48 31 6219 B0.5 la 5.58 329.98 -8.47 2100 20.00 87.00 580.00 860.00 0.020000 29.0 18.0 1.00 54 33 6294 B6 V+B7 V 6.27 1.62 14.41 200 -0.24 0.02 1.00 0.19 -0.000007 5.0 40 166
© Astronomical Society of the Pacific Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1133
Table 2 (Continued) cu HR Name Type 1 b d fl2 *25 ÍÓO fioo F IR^Bol θ R T25/60 Τ60/100 (deg) (deg) (pc) (Jy) (Jy) (Jy) (Jy) (arcmin) (pc) (cm' ) (K) (K) 6340 B6IV 6.30 1.91 12.39 280 0.52 0.50 9.40 21.00 0.001600 7.0 0.6 2.50 46 29 6387 B9 6.14 356.95 6.74 150 1.00 1.20 11.00 6.00 0.003600 5.0 0.2 15.00 51 50 6414 B5 Vnn+B5 V 5.88 22.73 21.57 180 0.67 0.84 5.20 19.00 0.000650 9.0 0.5 1.20 54 25 6453 42 θ Oph B2IV 3.27 0.46 6.55 190 8.80 25.00 87.00 180.00 0.001200 17.0 0.9 1.20 60 29 6532 B9.5V 6.42 34.98 22.90 150 0.75 0.66 3.20 8.70 0.002100 6.0 0.3 6.90 56 27 6601 B1.5V 6.30 18.67 11.58 310 5.20 16.00 100.00 52.00 0.001400 21.0 1.9 0.66 54 52 6712 66 Oph B2 Ve 4.64 30.99 13.37 210 2.20 1.50 1.40 2.20 0.000033 6.0 0.4 0.08 78 32 6736 9 Sgr 08 If 5.97 6.01 -1.20 1800 3600.00 15000.00 95000.00 93000.00 1.100000 20.0 11.0 96.00 54 38 6762 B0.5 Ib 6.28 8.93 -0.44 1600 17.00 110.00 1100.00 3600.00 0.052000 6.3 3.0 16.00 50 26 6788 B1 V 6.16 358.45 -7.10 740 0.30 1.70 2.90 -2.40 0.000160 6.0 1.3 0.11 69 6808 B9V 6.33 326.26 -22.05 160 0.66 0.38 3.00 6.00 0.001300 7.0 0.3 3.50 52 6938 δ2 Tel Β3ΙΠ 5.07 349.23 -15.91 380 2.10 1.50 2.70 0.20 0.000150 8.0 0.9 0.15 67 6941 B2V 6.69 34.13 6.60 440 2.50 2.50 42.00 95.00 0.002800 11.0 1.4 1.80 47 28 7029 B2.5V 4.87 359.80 -14.08 240 -5.00 -14.00 76.00 86.00 0.001100 29.0 2.0 0.52 36 7030 B8V 6.41 60.81 15.74 190 0.68 0.04 5.50 16.00 0.001900 9.0 0.5 3.50 36 26 7035 B5: V 5.83 9.73 -9.76 180 9.90 7.70 59.00 120.00 0.004400 10.0 0.5 7.50 52 29 7171 B7 ni-IV 6.50 51.45 7.34 370 0.56 0.53 5.80 22.00 0.001900 10.0 1.1 1.60 49 25 7173 B2Vp 6.75 42.85 2.88 370 -2.20 -4.40 7.80 -74.00 -0.000600 16.0 1.7 -0.32 7185 B5IV 6.41 69.51 15.36 420 0.34 0.19 1.30 3.50 0.000400 5.0 0.6 0.59 53 27 7200 B2IV-V 6.69 52.67 7.25 650 2.10 2.50 13.00 57.00 0.002900 13.0 2.5 1.10 56 24 7202 B5V 5.69 57.62 9.65 200 0.06 -0.31 4.60 4.70 0.000270 9.0 0.5 0.45 38 7270 B9 6.30 7.95 -16.96 160 0.68 2.00 16.00 38.00 0.007800 9.0 0.4 17.00 52 28 7287 21 Aql Β8Π-ΙΠ 5.15 37.52 -3.90 490 2.00 1.80 20.00 28.00 0.001800 7.0 1.0 1.70 49 33 7342 46 υ Sgr B2 Vpe+A2 la 4.61 21.84 -13.77 170 130.00 47.00 11.00 5.80 0.000440 4.0 0.2 2.00 119 51 7361 B9pHgMn 6.52 95.51 21.33 170 1.90 1.70 6.40 24.00 0.004600 14.0 0.7 5.90 58 25 7364 B9.5V 6.40 54.57 2.32 150 0.35 0.58 2.10 0.67 0.001300 6.0 0.3 4.50 60 73 7397 Β6ΠΙ 5.85 39.79 -6.85 290 1.10 0.45 4.30 10.00 0.000490 5.0 0.4 1.00 50 28 7418 6ß2Cyg B8 Ve 5.11 62.12 4.57 110 32.00 8.70 2.90 -4.30 0.001000 8.0 0.3 3.50 104 7474 44 σ Aql B3V+B3V 5.17 43.27 -8.07 170 19.00 32.00 170.00 420.00 0.005900 20.0 1.0 5.30 55 28 7567 B1ΙΠ+Β3 V 5.69 75.22 7.13 820 0.40 0.50 3.70 10.00 0.000220 3.0 0.7 0.27 53 27 7593 57 Aql B7Vn 5.71 32.66 -17.76 170 4.60 4.60 37.00 110.00 0.008600 10.0 0.5 15.00 52 26 7664 B9pHgMn 5.67 55.58 -7.97 130 0.69 -0.08 8.00 25.00 0.002300 11.0 0.4 5.10 26 7668 6.53 8.38 -29.04 210 0.44 0.81 2.40 -2.20 0.001100 11.0 0.7 1.50 62 7678 Β 1.5 lae 5.64 69.49 0.39 1100 10.00 150.00 1000.00 860.00 0.010000 20.0 6.5 1.40 53 41 7709 B1 V 6.49 33.97 -21.71 880 1.20 0.45 4.90 9.60 0.000310 9.0 2.3 0.12 49 30 7710 65 θ Aql B9.5 ID 3.23 41.58 1.50 0.36 3.20 5.80 0.000095 9.0 0.2 0.52 51 31 7716 Β libe 6.26 61.57 -6.45 2000 -1.90 2.20 3.10 -24.00 -0.000540 11.0 6.4 -0.07 71 7844 45 ω 1 Cyg B2.5 IV 4.95 86.07 5.74 290 53.00 62.00 590.00 1500.00 0.028000 31.0 2.6 9.70 51 27 7881 υ Pav B9III 5.15 328.39 -35.58 150 0.58 0.15 5.60 9.30 0.000700 6.0 0.3 2.40 42 31 7894 28 Vul B5IV 5.04 67.00 -10.35 210 0.53 2.80 8.60 29.00 0.000970 9.0 0.6 1.60 61 25 7940 B2m 6.32 93.88 9.00 470 0.40 6.30 20.00 5.40 0.000630 14.0 1.9 0.30 61 87 7977 55 Cyg B3Iae 4.84 85.75 1.49 1000 18.00 53.00 340.00 460.00 0.005100 15.0 4.5 1.00 54 34 7993 B0.5V 6.45 99.94 12.61 710 1.40 2.60 17.00 46.00 0.000600 11.0 2.3 0.24 54 27 8007 B2 ΙΠν 6.56 72.75 -10.48 990 0.10 1.70 17.00 4.60 0.001700 12.0 3.5 0.44 51 84 8020 B8Iae 5.67 87.51 1.42 1800 25.00 20.00 160.00 490.00 0.012000 8.0 4.2 2.50 52 26 8047 59 Cyg Bine 4.74 88.03 0.97 340 4.00 6.70 32.00 83.00 0.000490 10.0 1.0 0.44 57 27 8105 B1 Vp 6.54 81.05 -8.08 890 -0.18 -0.02 1.80 4.00 0.000079 7.0 1.8 0.04 29 8153 B2me 6.42 98.00 6.53 590 20.00 56.00 790.00 1300.00 0.041000 11.0 1.9 20.00 48 31 8154 68 Cyg 08e 5.00 87.61 -3.84 640 120.00 460.00 4500.00 7600.00 0.015000 57.0 11.0 1.30 50 31 8171 6 Cep B3 IVe 5.18 102.74 10.69 260 24.00 25.00 320.00 610.00 0.016000 12.0 0.9 16.00 49 30 8176 B3IV 6.38 309.46 -31.74 360 1.00 0.90 6.20 28.00 0.000790 8.0 0.8 0.85 53 24 8357 B6IV-V 5.71 99.56 1.28 250 0.78 2.10 12.00 46.00 0.002600 5.0 0.4 6.40 55 25 8371 13 Cep B8Ib 5.80 100.39 1.68 670 4.30 3.30 23.00 74.00 0.000960 5.0 1.0 0.90 53 26 8384 B2V 6.43 106.55 9.00 480 5.30 2.30 1.20 5.10 0.000260 4.0 0.6 0.42 90 24 8385 18 Peg B3ffl 6.00 65.80 -36.51 560 0.37 -0.93 1.80 1.10 0.000027 9.3 1.5 0.02 47 8425 α Gru B7IV 1.74 350.00 -52.47 36 2.70 1.50 1.30 -0.40 0.000008 6.0 0.0 0.11 79 8490 B8Vn 6.11 106.20 5.53 180 1.50 1.80 16.00 33.00 0.005500 4.0 0.2 24.00 51 29 8523 2 Lac B6V 4.57 97.79 -8.86 120 0.25 0.25 2.70 1.00 0.000078 7.0 0.2 0.29 49 65 8539 52π Aqr B1 Ve 4.66 66.01 -44.74 320 29.00 18.00 180.00 220.00 0.001300 48.0 4.5 0.26 50 35 8541 4 Lac B9 lab 4.57 99.90 -6.71 1300 1.30 0.86 5.50 13.00 0.000480 7.0 2.7 0.16 53 28 8549 B2V 6.46 93.58 -17.05 550 -0.30 1.70 9.30 6.40 0.000620 8.0 1.3 0.44 55 45 8603 8 Lac B2 Ve 5.73 96.38 -16.15 400 0.26 3.20 26.00 50.00 0.001300 10.0 1.2 1.00 52 30 8677 B9.5IV 6.36 107.31 -0.57 200 1.40 4.40 39.00 76.00 0.022000 4.3 0.2 79.00 51 30 8690 14 Lac B3 IV:e 5.92 100.04 -15.47 310 0.84 0.43 2.80 6.30 0.000190 6.0 0.5 0.32 53 29 8733 B2IV-V 6.18 100.07 -18.46 650 4.50 4.40 60.00 120.00 0.006600 20.0 3.8 1.60 48 29 8762 1 o And Β6ΙΠρβ+Α2ρ 3.62 102.21 -16.10 120 16.00 24.00 220.00 470.00 0.004800 25.0 0.9 4.90 51 , 29 8768 B2V 6.39 103.11 -14.59 440 -0.32 2.40 6.30 7.10 , 0.000360 11.0 1.4 0.23 63 36 8854 BOVn 6.53 112.02 1.12 650 5.60 25.00 280.00 450.00 0.003400 6.0 1.1 2.70 50 32 8873 Β8ΙΠ 6.32 102.31 -24.37 310 0.08 0.38 2.50 5.80 0.000990 5.0 0.5 2.00 54 28 8887 64 Peg B6m 5.32 101.57 -27.32 270 0.85 0.48 4.80 9.00 0.000420 7.0 0.6 0.69 50 30 8965 17 ι And B8V 4.29 109.03 -17.62 78 1.10 0.67 5.60 7.30 0.000260 7.0 0.2 1.50 51 34 9006 σ Phe B3V 5.18 326.59 -63.85 230 -0.60 0.01 6.00 9.30 0.000140 12.0 0.8 0.16 31 32 9070 B4 Ven 6.54 113.55 -15.50 340 0.61 0.84 3.00 3.40 ' 0.000720 7.0 0.7 0.93 60 36 9071 8 α Cas B1 V 4.88 115.55 -6.36 370 2.10 4.30 34.00 45.00 0.000420 12.3 1.3 0.28 52 34 9091 ζ Sel B4III 5.01 16.55 -78.90 330 -0.35 0.50 2.70 3.00 0.000092 8.0 0.8 0.11 56 36 9105 Β9ΠΙ 6.01 113.72 -19.94 180 16.00 6.40 1.80 0.94 0.001500 6.0 0.3 4.40 110 52
per limits to the density of dust-bearing gas at the positions lated using the V apparent magnitude, B—V color index, of these stars, depending on their distances and spectral spectral type, and luminosity class as given in The Bright types, but we have not done so in this paper. Star Catalog, along with the intrinsic colors and bolometric The spectroscopic distances listed in column 7 of Table corrections given by Flower ( 1977) and the absolute visual 2 (as well as those used for the non-hotspots) were calcu- magnitudes of Corbally and Garrison (1984). In the 31
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1134 GAUSTAD AND VAN BUREN cases where no color index is listed in The Bright Star Table 3 Catalog, we have estimated B—V from information con- Hotspots with Reflection Nebulosity 2 tained in the SIMBAD data base. If no luminosity class is 41 PB 482 PB 548 PB 561 PB 950 PB given in The Bright Star Catalog, we assumed the star to be 1035 PB 1092 EJ 1142 PB 1144 PB 1149 PB on the main sequence, of luminosity class V. The ratio 1151 PB 1165 PB 1307 PB 1399 PB 1555 PB 1659 PB 1660 PB 1712 PB 1719 PB 1735 PB AV/E{B— V) =3.0 was assumed throughout. 1750 PB 1808 PB 1810 PB 1847 PB 1861 PB The apparent bolometric magnitude was converted to a 1868 PB 1875 PB 1928 PB 1934 PB 1945 PB -5 bolometric flux FBol using the calibration 2.48 X10 1962 PB 2111 PB 2276 PB 2451 EJ 2538 PB -2 _1 2627 PB 2678 PB 2769 EJ 3088 EJ 3147 EJ erg cm s for mBol=0 (Allen 1973). The infrared flux 3223 EJ 3525 EJ 3536 EJ 4583 EJ 4743 EJ Fir was calculated by summing the intensities in the four 5027 EJ 5336 EJ 5375 EJ 5685 PB 5904 PB IRAS bands multiplied by their bandwidths (Beichman et 5944 PB 5988 PB 5993 PB 6027 PB 6028 PB 6084 PB 6294 PB 6340 PB 6532 PB 6762 PB al. 1988). For those cases in which the 12 μτη intensity is 6788 EJ 7035 PB 7171 PB 7185 PB 7200 PB larger than that at 25 μπι, indicating a contribution from a 7287 PB 7593 PB 7678 PB 7844 PB 7894 PB 8007 PB 8020 PB 8047 PB 8153 PB 8171 PB hot point source (such as a circumstellar shell), we first 8176 EJ 8490 PB 8854 PB 8887 PB subtracted from the intensity at each band an intensity equal to that at 12 μτη multiplied by the inverse fourth PB ~ Palomar Sky Survey Blue Plate power of the ratio of the band wavelengths, i.e., assuming EJ ~ ESO Sky Survey J Plate an emissivity inversely proportional to wavelength squared and the Rayleigh-Jeans approximation to the Planck func- scale, but some regions like Orion (/=210°, b= —20°) are tion. The ratio FiR/FBoi given in column 12 of Table 2, richer than others (/=340°, b= —10°) by more than would when multiplied by a factor of approximately 2 to account be expected if the distributions were statistically the same. for the infrared flux missed by the IRAS detectors, is equal Aside from the expected concentration toward the ga- to the absorption optical depth of the dust in the hotspot lactic plane, Fig. 2 also shows a concentration of hotspots surrounding the star. towards the plane of Gould's Belt, which intersects the The radius r of the hotspot, given in column 14 of Table galactic plane at longitudes 112° and 292° at an inclination 2, is calculated from the measured angular radius θ and of 18° (Allen 1973). This phenomenon is illustrated more spectroscopic distance d. The equivalent gas density n, clearly in Fig. 3, which is a projection onto a plane per- given in column 15, is calculated from the approximate pendicular to the line towards longitude 112°. Note that the relation (2). The color temperatures given in the last two median line for the hotspots slopes from lower left to upper columns of Table 2 were calculated by fitting a blackbody right, as does Gould's Belt. Errors in the distances may curve, multiplied by an emissivity inversely proportional to mean typical errors on this map of 30% in the star posi- wavelength squared, to the ratio of the fluxes (corrected as tions along a projected radius, however, so the interpreta- described above for any hot dust-like point source contri- tion that the hotspots are associated with Gould's Belt bution) at the two wavelengths indicated. A dash in this should be treated with caution. column indicates no fit could be found, usually because of Figure 4 is a map showing the distribution of hotspots a measured negative flux at one of the wavelengths. Mea- projected on the galactic plane to a distance of 400 pc. sured negative fluxes can arise when the background is Remember that distances are uncertain by roughly 30% on very structured and the source is weak, making it difficult these maps so there is significant radial mixing. Even so, to find the correct background level. the appearance of this map is strikingly different from Fig. In anticipation of future work, we examined the Palo- 2. There are distinct regions where hotspots are common mar Sky Survey and ESO Sky Survey at the position of and others where they are rare. In particular, within 75 pc each hotspot for evidence of reflection nebulosity. Of the of the sun there is a paucity of hotspots (and hence of 302 hotspots, 79 (26%) show extended emission which is dust), extending to larger distances roughly in the direc- brighter in the blue (POSS blue plate or ESO / plate) than tion of longitudes 80° and 260°. This can also be seen in Fig. in the red (POSS red plate or ESO R plate). These objects 5, which is a projection onto a plane perpendicular to the are listed in Table 3. line towards longitude 80°. A low density region about 60 pc wide roughly centered on the sun is clearly seen. Others 4. THE DUST DISTRIBUTION have referred to this phenomenon as the "local hole," but The distribution of program stars on the sky is shown in because the shape of the low density region appears more Fig. 2, which is an Aitoff equal-area projection in galactic linear than spherical, we suggest that "local trough" may coordinates. The larger symbols represent stars with de- be a more appropriate terminology. tected hotspots, i.e., those which are embedded in dust The significant grouping of hotspots at /= 170°, r = 150 clouds. When compared casually with the distribution of pc is the Taurus-Auriga dark cloud and star-forming re- all stars the hotspot distribution seems similar on a large gion and the one at /=350°, r=150 pc is the Sco-Cen region, which also contains the ρ Ophiuchi complex. While the density of our sampled stars also increases in these 2SIMBAD, an acronym for Set of Identifications, Measurements, and Bibliography for Astronomical Data, is a remotely accessible data bank regions, particularly Sco-Cen, the density of hotspots in- maintained by the Centre de Données Astronomiques de Strasbourg creases much more. This indicates that the star-forming (Egret et al. 1991). clouds are not isolated, but embedded in a halo of lower
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1135
Fig. 2—The distribution of the survey stars on the celestial sphere, mapped as an AitofF equal-area projection in galactic coordinates. The larger symbols represent hotspots, stars embedded in heated dust, the smaller symbols stars showing no detectable extended excess infrared emission.
-3 density material [nHe ( 1,10) cm ], whose precise mor- stand the selection effects inherent in our procedure and phology is not yet apparent. the completeness of our data. The nominal visual magni- Of course, the reality of the distribution patterns dis- tude limit of The Bright Star Catalog is 6.5, but about 200 played in Figs. 2-5 depends on the accuracy of the spec- stars brighter than this limit are not in the catalog, nor are troscopic distances. The HIPPARCOS mission is expected they included in our sample. Figure 6 is a histogram show- to provide parallaxes with 2-marcsec accuracy, and there- fore distances with ~ 10% uncertainties at our complete- ness limit of 150 pc. Once these become available, we will reexamine the three-dimensional distribution of cirrus hotspots.
5. COMPLETENESS In Sec. 6 we will determine the filling factor for the dust-bearing interstellar medium, but first we must under-
Y along 1=112 deg 100 υ 3 0 Ν -100 -200 -400 -200
Fig. 3—The distribution of the survey stars projected on a plane perpen- Fig. A—The distribution of the survey stars projected on the galactic dicular to the line towards /=112°, showing the concentration towards plane. A region of relative scarcity of hotspots roughly centered on the the plane of Gould's Belt. The meaning of the symbols is the same as in Sun and 60 pc wide, "the local trough," extends in the direction /= 80°- Fig. 2. 260°. The meaning of the symbols is the same as in Fig. 2.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1136 GAUSTAD AND VAN BUREN
200 100
0
-100 -200
Fig. 5—The distribution of the survey stars projected on a plane perpen- dicular to the line towards /=80°, showing the paucity of hotspots along the "local trough." The meaning of the symbols js the same as in Fig. 2. o 2 4 log d (pc) ing the distribution of our program stars with apparent visual magnitude. The distribution turns over at F=6.3, Fig. 7—The distribution of the survey stars with spectroscopic distance. which we take as our completeness limit. We show the distances of all stars as a histogram in Fig. 7. The peak in the distribution occurs at about 180 pc, with some falloff from a constant slope in the previous bin, at nounced dip near 0°, so we do not think this is a serious 140 pc. This is consistent with the above limit: a B9.5 star effect. A crucial assumption in the following analysis is that with Μν=0Λ, the least luminous star in our survey, will have V=6.3 at a distance 150 pc. Coincidentally, this is the program stars provide a fair sampling of interstellar also the approximate scale height of the sample stars, so space. In principle we might expect that some stars of the slope is expected to have a break near here anyway. earlier spectral type, being on average younger, are still The incompleteness of our data beyond 150 pc is also ev- embedded in their natal dust clouds. The fraction of stars ident in Fig. 4. However, both Figs. 4 and 7 show that we embedded in dust clouds (and therefore showing hotspots) have in our sample many stars (those more luminous than would then be a decreasing function of spectral type. A class B9.5 V) beyond this limit, a fact we shall make use of first glance at Fig. 10 seems to show that this is the case, at in Sec. 6. Figure 8 shows histograms of the distribution of least for the Β stars, but we think a different selection effect the detected hotspots with flux in the four IRAS bands. is at work here. The earlier stars are also more luminous, Our primary selection criterion was based on detectability so can heat clouds of lower density to the point where they of extended 60 μιη emission. Figure 8 shows our data to be will be detectable above the IRAS flux limit. If we select reasonably complete to a level of about 5 Janskys at 60 μιη. only those hotspots which have a density above a certain Because of the brightness of the infrared sky near the ga- limit, as in Fig. 11, we see no trend in the fraction of hotspots with spectral type. This is true for all densities lactic equator, one might expect it to be difficult to distin- -3 guish hotspots from the background in this region. The above 0.5 cm . Some very young stars may still be in- distribution of the fraction of stars with detectable hotspots cluded in our sample, but since the majority are of spectral versus galactic latitude (Fig. 9) does not show any pro- type B6 and later, with main-sequence lifetimes of tens of millions of years, most will have moved away from their birthplace to a more random part of the interstellar me- 2.5 dium. We conclude that our program stars provide a fair sampling of the cirrus above a density of 0.5 cm-3 in the broad volume occupied by Β stars. We probably have not 2.0 - fairly sampled the interarm medium, since in external spi- ral galaxies the blue light (and hence the early-type stars) 1.5 - is tightly confined to the arms. ζ Several prominent far-infrared nebulae associated with oen stars in The Bright Star Catalog are not included in our list 1.0 - because they fail the requirement that the color tempera- ture peak on the stellar position. Among these are the bow- 0.5 shock nebulae around a Camelopardalis, ξ Ophiuchi, λ Orionis, τ Canis Majoris, λ Cephei, κ Cassiopeiae, δ Pic- 0.0 toris, and δ Scorpii (Van Buren and McCray 1988). Also 0 2 4 6 8 V missing is the cirrus cloud near a Virginis, which has a complicated structure and apparently does not actually in- Fig. 6—The distribution of the survey stars with apparent visual clude the star, though the stellar position is projected magnitude. against the cloud.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1137
log F (Jy) log F (Jy)
log F (Jy) log F (Jy)
Fig. 8—The flux density distributions of the survey stars at the four IRAS wavelength bands.
6. THE FILLING FACTOR OF THE DUST-BEARING solute magnitudes such that they would be brighter than GAS F=6.3 at distance d (excluding the unexamined stars of Table 1). Among those which show hotspots, we select If the stars in our sample are distributed in an unbiased only those which satisfy the above criteria on flux and fashion relative to the cirrus, then the fraction which are density. If « is the number of hotspots and « the total embedded in dust clouds is equal to the fraction of space- hs tot number of stars so selected, the filling factor of gas with a containing dust. Although various selection effects may density > «' in the volume out to distance d is prevent detection of some embedded stars as hotspots, the η fraction of stars which show hotspots should be a lower f(n>n') = nhs(n>n')/ntot.(3) limit to the volume filling factor for the dust-bearing inter- Figure 12 shows the filling factor calculated in this way for stellar medium. The limit on apparent magnitude trans- lates into different distance limits for stars of different ab- volumes of radius out to 1000 pc. The "local hole" or "local trough" is evident: The filling factor for the volume solute magnitudes. To calculate the filling factor within a out to 150 pc is 7.1 ±1.3%, whereas that for the volume volume to a distance d, we select all stars which have ab- 0.501 I ^ ^ ι ^ Π ^ ι ι I ^ ^ 0.50 _ 0.40 - 0.40 -
•| 0.30 - σ "δCL I-S 0.20-
0.10 - 0.00 I I ι I ι I ι ^^^ ι ι ^ ι ^^ ι ι 0.00 _ 06 07 08 09 B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 -90-80-70-60-50-40-30-20-10 0 10 20 30 40 50 60 70 80 90 Spectral Type Goloctic latitude Fig. 10—The distribution of hotspot fraction with spectral type for all Fig. 9—The distribution of hotspot fraction with galactic latitude. densities.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1138 GAUSTAD AND VAN BUREN
d < 400 pc M < -1.7 V < 6.3 f60 > 5.0 Jy .
06 07 08 09 BO B1 B2 B3 B4 B5 B6 B7 B8 B9 0.0 -3 Spectral Type ' log η (cm )
Fig. 11—The distribution of hotspot fraction with spectral type for den- Fig. 13—Volume filling factors as a function of density for the region -3 within ¿=400 pc. sities above «=0.5 cm . out to 400 pc, e.g., is 14.6 ±2.4%. Note that there are no We have derived a filling factor of 0.15 for the dust- stars in our sample within 50 pc which are found within bearing interstellar medium above a density of 0.5 cm-3. If clouds of density >0.5 cm-3. the power-law distribution described above continues to The filling factor as a function of density for the volume higher densities, clouds more dense than 10 cm-3 have a out to 400 pc is shown in Fig. 13. Above a density of 1.0 filling factor of only 0.01. By comparison, the medium with cm-3, the filling factor (per unit log n) appears to follow a electron densities around 0.2 cm-3, to which we are not power law with density with a power-law index of —1.25, sensitive in a complete sense, has an estimated volume fill- i.e., ¿f(log/)A/(logn) = —1.25. As was discussed in Sec. ing factor of 0.2 (Reynolds 1991). If these two media are 5, we believe our sample is complete to density 0.5 cm-3. distinct, then it leaves a fractional volume as little as ~0.6 Support for this belief comes from the fact that available for the very low density (and presumably hot) 2 <[í/cos ¿>/í/max] >, the two-dimensional V/Vmax statistic gas. It is of interest to view Fig. 7 (Plate 11) of Bregman (Schmidt 1968), is 0.36 and 0.38 for the samples with 0.5 et al. (1993) in this context, particularly noting that their cm-3 < « < 1.0 cm-3 and η > 1.0 cm-3, respectively, not a best match of the amplitude of the observed 21 cm surface significant difference. (The fact that these are both less brightness fluctuations is with an ISM model having a vol- than the value 0.5 expected for a uniform density disk we ume fraction 0.57 to 0.75 in holes. attribute to selection effects based on increased extinction and decreased angular size with distance, and the fact that the distribution is not strictly two-dimensional. ) The devi- -3 7. COMPARISON WITH THE MURTHY ET AL. ation from a power law between densities 0.5 and 1.0 cm RESULTS may therefore be real, but the apparent decrease of the filling factor at even lower densities probably reflects the Our result for the volume filling factor ( 14.6% ±2.4%) inadequacy of our technique for detecting very low density agrees with the estimate of 20% ± 10% obtained in the (and hence low surface brightness) regions. pilot study by Van Buren ( 1989). It is similar, in the sense of being fairly large, to the filling factor for the Η I gas (20%-50%) obtained by Bregman et al. (1993). It is in serious disagreement with the result of Murthy et al. ( 1992, hereafter referred to as MWH), who obtain a filling factor of 0.6%. In this section we present our understand- ing of the reasons for this discrepancy. The set of stars examined by MWH overlaps but is not identical with ours. Our survey considered all O and Β stars in The Bright Star Catalog. MWH added cooler stars of luminosity class I, but excluded stars within 10° of the Galactic plane or in the direction of several nearby molec- ular clouds. Comparison of their list of hotspots with ours, where our samples do overlap, indicates that they have some extra objects (e.g., HR 179, 1320, 6175, 7128, to list 400 600 Maximum Distance (pc) some of the brightest) and miss some that we have found (e.g., HR 811, 1174, 1443, 1600, and 1660). Where both Fig. 12—Volume filling factors as a function of maximum distance sur- groups have looked at the same stars, the agreement on veyed for densities greater than «=0.5 cm-3. detections is only about 50%. We trace many of the incon-
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System DISTRIBUTION OF INTERSTELLAR DUST 1139 sistencies between our hotspot catalogs to differences in the ume within which they assume clouds would be detected. definition of a hotspot, and differences in the observational MWH's modeling could be justified if dust properties and material and methodology. the local radiation field were well enough known and if as The input data set used by MWH was very different a result of the modeling, dust clouds were found to have a from our own. They used the IRAS SkyFlux plates, while statistically uniform spatial distribution. To test whether we used BigMaps, which are essentially the same product the MWH clouds are uniformly distributed in space near as the Infrared Sky Survey Atlas (ISSA). The SkyFlux im- their illuminating stars we calculated the distribution of ages typically include only one-third of the survey data and the d values from their Table 2. We find that the cumula- contain both the zodiacal emission and "stripes" due to tive counts go roughly as n{d © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 1140 GAUSTAD AND VAN BUREN debted to the taxpayers of the United States, the United On-line Data in Astronomy, ed. M. Albrecht and D. Egret Kingdom, and the Netherlands, who collectively made the (Dordrecht, Kluwer), p. 79 IRAS mission possible. Flower, P. J. 1977, A&A, 54, 31 Good, J. C, and Gautier, T. Ν. 1986, BAAS, 18, 1023 Hoffleit, D., and Jaschek, C. 1982, The Bright Star Catalog, 4th REFERENCES revised ed. (New Haven, Yale University Observatory) Allen, C. W. 1973, Astrophysical Quantities, 3rd ed. (London, Houk, N., and Cowley, A. P. 1975, University of Michigan Cat- Athlone), pp. 197 and 282 alogue of Two-Dimensional Spectral Types for the HD Stars Beichman, C. Α., Neugebauer, G., Habing, H. J., Clegg, P. E., (Ann Arbor, University of Michigan, Department of Astron- and Chester, T. J. 1988, Infrared Astronomical Satellite omy) (IRAS) Catalogs and Atlases, Explanatory Supplement Low, F. J., et al. 1984, ApJ, 278, L19 (Washington, DC, NASA), p. X-13 Murthy, J., Walker, H. J., and Henry, R. C. 1992, ApJ, 401, 574 Bohlin, R. C, Savage, B. D., and Drake, J. F. 1978, ApJ, 224, 132 (MWH) Boulanger, F., Baud, Β., and van Albada, G. D. 1985, Lecture Reynolds, R. J. 1991, in IAU Symp. 144, The Interstellar Disk- Notes in Physics, 237, 28 Bregman, J. N., Kelson, D. D., and Ashe, G. A. 1993, ApJ, 409, Halo Connection in Galaxies, ed. H. Bloemen (Dordrecht, 682 Kluwer), p. 67 Corbally, C. J., and Garrison, R. F. 1984, in The MK Process Savage, B. D., and Mathis, J. M. 1979, ARAA, 17, 73 and Stellar Classification, ed. R. F. Garrison (Toronto, David Schmidt, M. 1968, ApJ, 151, 393 Dunlap Observatory), p. 277 Terebey, S., and Fich, M. 1986, ApJ, 309, L73 Draine, Β. T., and Lee, H. M. 1984, ApJ, 285, 89 Van Buren, D. 1989, ApJ, 338, 147 Egret, D., Wenger, M., and Dubois, P. 1991, in Databases and Van Buren, D., and McCray, R. 1988, ApJ, 329, L93 © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System