198 7Apj. . .312L. .11J the Astrophysical Journal, 312:L11-L15
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.11J The Astrophysical Journal, 312:L11-L15,1987 January 1 .312L. © 1987. The American Astronomical Society. All rights reserved. Printed in U.S.A. 7ApJ. 198 INTERSTELLAR DUST IN SHAPLEY-AMES ELLIPTICAL GALAXIES M. Jura and D. W. Kim Department of Astronomy, University of California, Los Angeles AND G. R. Knapp and P. Guhathakurta Princeton University Observatory Received 1986 August 11; accepted 1986 September 30 ABSTRACT We have co-added the IRAS survey data at the positions of the brightest elliptical galaxies in the Revised Shapley-Ames Catalog to increase the sensitivity over that of the IRAS Point Source Catalog. More than half of 7 8 the galaxies (with Bj< \\ mag) are detected at 100 /xm with flux levels indicating, typically, 10 or 10 M0 of cold interstellar matter. The presence of cold gas in ellipticals thus appears to be the rule rather than the exception. Subject headings: galaxies: general — infrared: sources I. INTRODUCTION infrared emission from the elliptical galaxy in the line of sight. The traditional view of early-type galaxies is that they are Our criteria for a real detection are as follows: essentially free of interstellar matter. However, with advances 1. The optical position of the galaxy and the position of the in instrumental sensitivity, it has become possible to observe IRAS source agree to better than V. (The agreement is usually 21 cm emission (Knapp, Turner, and Cunniffe 1985; Wardle much better than T.) and Knapp 1986), optical dust patches (Sadler and Gerhard 2. The flux is at least 3 times the r.m.s. noise. 1985; Ebneter and Balick 1985; Sparks et al 1985; Hansen, 3. The source is detected in more than one IRAS band. Norgaard-Nielsen, and Jorgensen 1985; Gallagher 1986) and 4. The infrared colors generally resemble those of galaxies thermal X-ray emission (Forman, Jones, and Tucker 1985) (de Jong et al. 1984; Jura 1986a). from some of these galaxies as well as ionized gas that Some of the apparent detections listed in Table 1 are of low produces optical emission Unes (Phillips et al. 1986). Jura weight and may not be the result of the elliptical galaxy in the (1986a) and Tytler (1986) have used the infrared emission observed direction. In order to check for the possibility of given in the IRAS Point Source Catalog to study their dust galactic cirrus (Low et al. 1984) or other contaminating sources content. Currently, we are undertaking an extensive project to in the beam, we have obtained co-added IRAS data for 18 co-add the IRAS data to reach a greater level of sensitivity randomly chosen locations of sky with \b\ > 30°. In this than available with the Point Source Catalog in a comprehen- sample, we find no “detections” at 12 jLim; one “detection” at sive statistical study of dust in early-type galaxies. Because 25 /xm; no “detections” at 60 /xm; and two “detections” at our initial results are so striking, we report here the data for 100 /xm. None of these “sources” appeared in more than one the brightest elliptical galaxies in the Revised Shapley-Ames IRAS band. Therefore, the galaxies that are detected only at Catalog (Sandage and Tammann 1981). Details of the data IRAS band at either 60 /xm or 100 /xm are quite possibly and analysis will be presented in later papers. spurious, and they are noted as such in Table 1. There are seven such objects out of the 58 that we have measured; this II. DATA ANALYSIS is consistent with a rate of -15% apparent detections found in the randomly chosen positions. The presence of cirrus We have used the one-dimensional co-adding procedure emission is also apparent in several of our observations; the provided by the Infrared Processing and Analysis Center noise in the 100 /xm data is sometimes much higher than the (IPAC) to analyze the IRAS data for all elliptical galaxies instrumental noise. The high value of the r.m.s. noise for the brighter than = 12.0 mag in the Revised Shapley-Ames 100 /xm observations of NGC 185 and NGC 221 Usted in Catalog, except for NGC 3078 and NGC 3608 which are in Table 1 is due to the proximity of M31. portions of the sky not scanned by IRAS. The preliminary fluxes for these 58 galaxies, along with the classifications given by Sandage and Tammann (1981), the fluxes at B converted to mJy, and the distances from the prescription III. RESULTS given by Knapp, Turner, and Cunniffe (1985) with Virgo- The elHptical galaxies Usted in Table 1 are strongest at 12 -1 -1 centric flow and H0 = 100 km s Mpc are given in Table /xm and 100 /xm. At 12 /xm it is likely that the emission 1. The 1 a errors are quoted for all detections; 3 a upper mainly arises both from the photospheres of stars and from limits are given for nondetections. dust in circumstellar envelopes around mass-losing red giants Most of the positive results shown in Table 1 indicate real (Soifer et al 1986; Impey, Wynn-WilUams, and BeckUn 1986). © American Astronomical Society • Provided by the NASA Astrophysics Data System .11J .312L. TABLE 1 Fluxes from Shapley-Ames Ellipticals2 7ApJ. Fv (mJy) M M D FP(B) 1 7 198 Galaxy (Mpc) (mJy) 12 /Ltm 25 /um 60 ¿im 100/un (M0 yr' ) (10 M0) B® < 10.0 mag NGC 147(dE5) . 0.7 460 < 87 < 63 < 135 < 540 2.2(-4) < 0.0042 NGC 185(dE3p) 0.7 570 < 90 < 75 420(24) 1500: (202) 2.3(-4) 0.012 < 255 < 4200 l.l(-3) < 0.033 NGC 221 (E2)... 0.7 1350 450(39) 230(36) a NGC 4486(E0).. 13.5 630 290(34) < 153 330(40) 440(93) 0.27 1.3 10.0 <B^< 11.0 mag < 87 340(82)b 0.077 0.91 NGC 1399(E1) 12.9 214 90(25) < 60 b NGC 1407(E0) 16.4 189 < 69 87 120(30) 480(74) < 0.10 2.1 < 66 180(55)b 0.044 0.25 NGC 1549(E2) 9.3 233 100(20) 60(16) c NGC 3379(EO) 7.6 327 220(42) 153 < 123 < 327 0.065 < 0.30 NGC 4125(E6) 18.9 220 < 117 72 620(44) 1670(69) < 0.22 9.5 < 732 0.14 < 2.1 NGC 4365(E3) 13.5 256 150(35) 147 < 132 b NGC 4374(E1) 115 359 200(38) 190(42) 500(27) 1280(94) 0.19 3.7 NGC 4494(E1) 12.9 224 < 90 123 < 108 < 510 < 0.08 < 1.4 < 141 < 282c 0.18 < 0.82 NGC 4621(E5) 13.5 240 190(44) 129 b NGC 4697(E6) 11.7 401 290(24) 123 330(23) 1240(76) 0.20 2.7 420(37) 1000(76)b < 0.21 9.8 NGC 5322(E4) 24.7 192 < 66 63 b IC 1459(E4)... 14.8 183 170(29) 230(44) 450(31) 1180(103) 0.19 4.1 11.0 < Bj< 12.0 mag NGC 596(E0).. 18.4 79 < 105 < 162 78 < 339 < 0.18 < 1.8 123 < 189c 0.13 < 0.83 NGC 720(E5).. 16.6 154 90(28) < 123 b,c NGC 821 (E6).. 17.5 78 < 99 < 201 123 500(130) < 0.16 2.5 NGC 1275(Ep) 52.5 76 860(34) 3820(39) 5760(63) 7500(200) 12 330 78 390(61)b 0.15 1.5 NGC 1395(E2). 15.7 150 120(28) < 87 b,c NGC 1404(E2). 17.9 167 < 132 < 75 84 290(56) < 0.22 1.5 111 < 147 < 0.062 < 0.52 NGC 1427(E5). 14.9 74 < 54 < 63 b,c NGC 1537(E6). 12.1 105 < 96 < 48 81 280(82) < 0.072 0.66 NGC 1700(E3). 38.3 84 < 111 < 102 < 90 < 654 < 0.84 < 15 NGC 2325(E4). 21.8 86 < 99 < 66 < 159 < 630 < 0.24 < 4.8 NGC 2300(E3) 22.3 71 < 60 90 < 105 < 276 < 0.15 < 2.2 NGC 2974(E4). 22.5 94 < 69 87 420(33) 1900(53) < 0.18 15 NGC 2986(E2). 25.2 82 < 84 90 < 60 < 192 < 0.27 2.0 NGC 3136(E4). 15.8 120 < 75 75 < 168 < 249 < 0.096 < 1.0 NGC 3193(E2). 18.6 82 < 105 144 < 114 < 1083 < 0.19 < 6.0 < 177 < 441 0.82 < 5.9 NGC 3250(E3). 29.0 85 190(56) 120(21) b NGC 3377(E6). 6.0 161 < 105 < 216 170(45) 350(60) < 0.02 0.20 190(46) 750(169)b 0.69 12 NGC 3557(E3). 32.1 143 130(26) < 84 b c NGC 3610(E5). 23.0 107 < 108 < 63 < 93 280(86) ’ < 0.29 2.4 NGC 3613(E6). 25.7 97 < 81 < 99 < 78 < 258 < 0.28 < 2.7 NGC 3640(E2). 12.0 139 < 123 < 129 < 117 < 198 < 0.091 < 0.46 NGC 3706(E4). 31.2 75 < 96 < 135 < 123 < 336 < 0.48 < 5.2 < 168 < 627 < 0.20 < 3.4 NGC 3904(E2) 18.5 82 < 114 < 120 c NGC 3962(E1). 22.3 101 < 108 < 177 280(50) < 903 < 0.28 < 7.2 NGC 4261(E3). 11.7 125 < 174 < 195 < 135 < 585 < 0.12 < 1.3 NGC 4278(E1). 7.9 157 < 129 < 96 590(56) 1930(99) < 0.041 1.9 NGC 4373(E4), 35.1 80 87 < 93 < 138 < 699 < 0.55 < 14 IC 3370(E2p) . 30.5 76 102 < 165 520(35) 1910(119) < 0.49 28 NGC 4473(E5) 13.5 166 144 < 120 < 183 < 321 < 0.14 < 0.94 < 195 < 636 < 0.12 < 1.9 NGC 4564(E6) 13.5 79 132 < 144 b NGC 4589(E2) 24.8 84 96 < 90 200(31) 660(168) < 0.30 6.5 < 144 < 339 < 0.12 < 0.99 NGC 4660(E5) 13.5 79 126 183 b NGC 4696(E3) 30.6 127 105 87 100(27) 770(155) < 0.51 12 NGC 5018(E4) 31.4 97 160(31) 210 1020(40) 2030(96) 0.81 32 NGC 5044(E0) 29.9 79 < 138 291 < 159 < 312 < 0.63 < 4.5 < 102 < 480 0.38 < 4.1 NGC 5061(E0) 23.1 139 140(23) 117 b IC 4296(E0)..