Statistical Properties of 6.7 GHz Methanol Maser Sources

Chin. J. Astron. Astrophys. Vol. 3, No. I, (2003) 49-68Chinese Journal of( ht:/wwchwa.orng or ht//hjaa.bao.ac.cn)Astronomy andAstrophysicsStatistical Properties of 6.7 GHz Methanol Maser Sources*Ye Xu 1,2, Xing Wu Zheng3 and Dong-Rong Jiang21 National Astronomical Observatories, Chinese Academy of Sciences, Urumqi 830011;xuye@nju.edu.cn2 Shanghai Astronomical Observatory, Chinese Acadeny of Sciences, Shanghai 2000303 Department of Astronony, Nanjing University, Nanjing 210093Received 2002 August 12; accepted 2002 September 23p1 AAbstract We present a statistical analysis of 482 6.7 GHz mnethanol maser sourcesfrom the available literature, on their maser emission and the characteristics oftheir associated infrared sources. On the color-color diagram, more than 70% ofthe objects fall within a very small region (0.57 ≤[25- 12]≤1.30 and 1.30 ≤[60- 12]≤2.50). This suggests that 6.7 GHz methanol maser emission occurs onlywithin a very short evolutionary phase during the earliest stage of star formation.The velocity ranges of the masers belong to two main groups: one from 1 to 10km s-1, and one from about 11 to 20 km s~ 1. These velocity ranges indicate thatthe masers are probably associated with both disks and outflows. The correlationsbetween the maser and infrared fux densities, and between the maser and infraredluminosities, suggest that far-infrared radiation is a possible pumping mechanismfor the masers which most probably originate from some outer molecular envelopesor disks.Key words: masersISM: molecules一stars: circumstellar matter一stars:formation - ISM: HII regions1 INTRODUCTIONmaser emission at radio frequencies. Methanol maser emission arises from several transitions,the strongest being the 51 - 6oA+ line at 6.7 GHz, which is the second strongest Galactic maserof any molecule, first reported by Menten (1991) and recognized as typical of Class I masers.Class II methanol masers are always found in regions of recent Inassive star formation and manyof them are associated with known ultra-compact (UC) HlI regions - a very early phase inthe star formation process. Stars earlier than type B2 also give rise to bright hydroxyl andwater masers. However, hydroxyl and water nasers can also be found in the later stages ofa star's life, and interstellar water masers also occur around young stars later than type B2.* Supported by the National Natural Science Foundation of China.中国煤化工CNMHG60Y. Xu, X. W. Zheng & D. R. JiangHence, only met hanol masers are unique indicators of massive star-forming regions. At presentextensive surveys have yielded more than 400 6.7 GHz maser sites (Caswell et al. 1995; vander Walt et al. 1995, 1996; Ellingsen 1996; Lyder 1997; Walsh et al. 1997; Slysh et al.1999;Szymczak & Kus 2000). The widespread occurrence and high intensity of the 6.7 GHz maserline make it one of the best tracers of star-forming regions at present.Up to now, there does not seem to have been any systematic statistical study of all theknown methanol maser sources. In order to understand better the connection between methanolmasers and other phenomena typical of star formation region, such as the associated far-infraredsources, we have investigated the statistical properties of all known 6.7 GHz methanol masersources and found some interesting results.2 DESCRIPTION OF THE DATAWe have searched the literature for all known 6.7 GHz methanol maser sources and found atotal of 482 objects. Among these, 361 have IRAS identifications. All the data are tabulated inTable 1. The first four columns of Table 1 give the galactic coordinates, name of the associatedIRAS source and its 1950 equatorial coordinates. Colunns 5 to 7 give the peak radial velocity,the radial velocity range and the peak fux density. Colunn 8 is the distance. Some of thedistances are directly quoted from the references and those that have no published distancesare heliocentric kinematic distances, computed from the peak velocities of the 6.7 GHz methanolspectrum using the galactic rotation curve of Wouterloot & Brand (1989), and assuming Ro =8.5 kpc and日o = 220km s-1. Column 9 lists the references.3 DATA ANALYSIS3.1 Galactic DistributionThe distribution of all known methanol masers in the Galaxy is plotted in Fig. 1. It is seen50 F00 Fso f50 t-10000-150 - 100 s00100 150 200Calactic LongitudeFig.1 Distribution in longitude-latitude (upper panel) and longitude-velocity (lower panel)of all known methanol masers in the Galaxy.中国煤化工，YHCNM H云就缩子: lStatistical Properties of 6.7 GHz Melhanol Maser Sources51that the vast majority lies in the inner galaxy region. The number of masers is about 49%(235/482) in the first quadrant, and 44% (214/482) in the fourth quadrant, i.e, a ratio of1.1:1.0. This differs slightly from the results of Gaylard & MacLeod (1993) and MacLeod & .Gaylard (1992). About 74% (357/482) of the masers lie within |6 < 0.59， and only around11% (53/482) have galactic latitudes greater than 1°, (the largest is -12.6° for the source06053-0622).The distribution in the longitude-velocity diagram shows that the ma jority of the objectsare located in the 'molecular ring' and fllw the same distribution as the molecular gas (Dameet al. 2001). This is consistent with the result of van der Walt et al. (1995).3.2 Infrared Flux DensityOf the 482 6.7 GH methanol maser sources, 361 have IRAS identifcations. Almost 97%(346/361) of the soures satisfy the inequalities Fi2 < F25 < Foo < Floo, which characterize .the evolutionary stage of young sellar objects, the youngest ones having the steepest spectra,and this also indicates that the emission is mainly produced by cool dust (T≤30 K). About62% (23/361) of the objets have Foo > 500 Jy and only six objects have Fa0< 100Jy. It isevident that the 6.7 GHz methanol maser emission is much more likely to occur in sources withhigh 60 μm fuxes.3.3 Color-Color PlotTo analyze the infrared properties of the 6.7GHz methanol Inasers, we plotted the color-color diagram for the 361 IRAS identifed sources. Figure 2 shows the [25 - 12] vs. [60- 12] and[60- 12] vs. (60 - 25] diagrams (here [i - jil = log F/ER). The box on the upper right corner .05 1.0 1.52023 303.54.0log (F6o/ Fzs)Pig.2 IRAS clorcoloror diegramn for 361 oijcts. Upper panel: The box in the uper rightcorner delineates the WC89 criteria for UCHII regions More than 70% sources fall in averysmall region (the central box); 0.57≤(25-12]≤1.30 and 1.30≤[60- 12]≤2.50. Lowerpanel: The dotted line is the best ft line.中国煤化工。.MYHCNMHG32Y. Xu,X. w. Zheng & D. R. JiangTable 1 Parameters of CHgOHI SpectraSourceIRLASRA. ([1950) DEC (1950) Vvoak, Vange、 Speak D、INameNane121.24- 0.34 00338+6312 00 33 53.363 12 32-22.4 -27.-21 .10.9l963 1230.910123.06- 6.31 00491+5617 00 49 29.25617 31123.06- 6.31 00494+5617 00 49 29.256 17 37-29.0 -31,-2133.72+ 1.22 02219+6152 02 21 54.461 52 34-44.3 -47,-39 5133.95+1.07 02232+6138 02317.7 61 3858-44.6 -48,-31 3741 2.212136.84+1.14 02455+6034 02 45 30.16034 35-45.3 -46,-44 24 4.93 3, 5174.20- 0.08 05274+3345 05 27 27.633 45 372.1 0、+6941.811174.20- 0.08 05274+3345 052727.6 33 45 371.8 0,+5481.811 3,8173.48+2.43 05358+3543 05 3548.8354341.-13.6 -16,-11 256 1.811173.63+2.87 05379+3550 053759.533 5038173.70+2.89 05382+3547 05 3815.73547217.5 16.544183.35-0.58 05480+2545 05 4804.825 4529-14.5 -16,-14 19 2.147 3.5213.71- 12.6008053- -0622 06 0521.7-06 222810.5 +6,+13 337 0.811 4,9213.71-12.60 06053-0622 060521.712 +9,+13 166 0.811189.78+0.34 06055+2039 060536.617 1.5189.78+ 0.3406055+2039 06 05 36.620 39 30i5 1.5189.03+0.78 06056+2131 06 0541.121 313510.9 +9, +1321 31 359.2 +9.+1219189.03+ 0.78 06056+2131 06 0541.117188.95 + 0.89 08058+2138 06 05 53.510.4 +8,+12553188.95+ 0.89 06058+2138 06 05 53.521 39 02495188.80+ 1.0306061+21-5.54.8192.60- 0.0506099+1800 06 09 59.11200 15.L06 09 59.1.135024196.45- LG60617+ 1350，232.62+ 1.0007299-1651232.62+ 1.00 07299- 165107 29 55.0.-1651472.0259.94- 0.0408337- 4028 08 33 42.6- 4028 02263.25+ 0.52 08470-4243 08 47 00.5- 4243 1512 +11,+15 57.32.2264.29+1.46 08546- 425408 54 36.2-425406+6,+10 0.24,9269.46-1.47 09015-4843 0901 33.2 - 48 43 244.6269.16-1.14 09018- 4816 09 0150.3-48155716 +7.+16 14270.25 +0.8409149- -4743 091454.1- 47 4313.2284.35- 0.42102220.0 -57 37 25; +3,+112.1285.26- 0.05.57 46441030 19.3.10.0285.35+ 0.0010303-5746 10 3019.3-57 4658287.36 + 0.64 10460- 581110 46 03.4-5810 5863.8287.38 + 0.65 10460-5811 10 46 06.3-58111182290.41-2.91 10555-6242 10 5535.1-624250290:38+1.66 1101-5829 1007.7_ 582959291.57- 04311 9201605302291.58-0.4311 12 58.1-6053 40+9,+20 3.4293.83 - 0.75 11298-615511 2948.2- -61 554910.5293.95- 0.8911304- -6206 11 30 25.0.-6206273710.9294.51- 1.62 11332-6258 11 33 12.9-625815294.52- 1.62 11332-6258 11 33 15.0-625813295.00- 1.74 11368- - 631211 3704.8-63 1329-13,-12 26.3 1.5/5.7296.89-1.31 11543- -6315-631529.+21.5,+23 2.4298.22- 0.331207 16.9-6233 0137 +33,+39 1.5298.26+0.74 12091- -612912 0908.4-61293730 -31,-29 14 3.8/5.89299.02+0.13 12146-6212 12 1445.6-62 122218 +18,+20 4.59.94,8.9300.51-0.18 1222 -6240 1227 15.9-.6240251.7.3300.51-0.18 12272-6240300.97+1.15 12320-6122 12 3202.6-61 2306-37 -40,-36 5.0 4.99中国煤化工MYHCNMH alds.Statistical Properties of 6.7 GHz Methanol Maser SourcsTable 1 (continued)SourceIRAS RA. (1950) DEC (1950) Vpoak Vange Spak D.Name300.97 + 1.1512320-6122 12 32 02.2-61 2259-38,-363.9 4.99301.14- 0.2312326- 624512 32 42.6- 62 45 57-40 -41,-38 L.54,302.03 - 0.0612405- 623812 4034.5- 62 38 46-35-35. 9。 3.3/6.9302.02- 0.0812405-6238 12 40 29.5- 62 39 39-36,-34 10.8 3.3/6.99305.20 + 0.21130758.6 -62 18 42-44 -47,-43 50 4.6/6.99305.21 + 0.2113079- 6218 13080L.7 -621845 -38 - -42,-34480 4.4/5.44.9305.20 + 0.0213080- 6229130805.7- 62 29 58-33 -44,-29 52 3.3/6.5305.25 + 0.2513 08 20.5-62 16 07305.35 + 0.2013092-6218 1309 16.3- -62 18 36-33-39,-34305.36+ 0.15130924.2 - -6221 22-36 -39,-34305.37 + 0.19130926.3- -62 19 15305.55+0.02 116228 1311078 -622832305.89+ 0.0013140- 6226 13 14 02.9- 62 27 26 .10.8 3.1/6.8306.33- 0.3413180- 6245 13 18 07.3- 62 45 01240.3308.74 + 0.5513374-6130 13 3725.6- 61 30 19-40 11.2 4.9/5.7308.92 + 0.12133935.4- 61 53 47309.39 - 0.1413 43 55.9- 62 03 14309.92 + 0.4813471-6120 134711.9- -61 2019-60 -65,-53 780 6.30310.13+ 0.7513484-6100 134824.4 -61 01 30-58,-54 137.9310.18- 0.12.13504-6151 135027.9- -61 51 38311.63+ 0.2914013-6105 1401 18.2- -61 05 4558 - -63,-56 1.9 5.0/8.10311.64- 0.3814030-6144 14 03 00.9- 61 43 54+31, +35311.65-0.38 14030 -6144 14 0301.6 - -61 44 0632 +31,+36311.96+ 0.14140419.7- -61 08 343.1/8.3312.11 +0.3114050-6056 14 0505.2- -60 58 29312.12+ 0.2714054-6102 14 05 16.2. - 60 58 32-52,-48 15.0312.60 +0.04 14095-6102 14 09 36.2 -61 02 5788 -69,-59312.60+0.05 14095-610214 0936.3 -61 02 41-13,-19313.47+0.1914159-6038 14 1600.5 .-6038 014313.57 + 0.32.14164- 6028141624.4- 6028 55313.76- 0.8614212- - 61311421 25.0 -61 32 2744-57,-40314.26 + 0.1114222-6026 1422 14.2- 60 26 47314.26+0.1114222-6026 142214.2 -60 26 47-45,-43 20.7 3.4/8.4316.64 - 0.0914404 - 5942143031.6 -59 42 4020 -25,-14 128 1.5/10.6 4,316.40 - 0.3014 3927.1- 60 00 22316.36- 0.3614394-6004 14 3923.8- -60 04 3379.412614394-6004 143923.8- -60 0433143934.7- 6004 570.5/11.8316.81- 0.06 14416-5937 14 4139.3- -59 36 35316.81-0.07 14416-5937 14 4138.9 -59 3711SLE.TO +01014478-590 1447 18.9 - 5905 1318.05+ 0.0014498 _ 5856 14 4954.0- 58 56 43.318.05- 1.4114551- 6016 14 55 14.5; - 601624+44,+47318.78 - 0.1514557-5849 14 5543.8. - 58 49 272.5/10.3318.95- 0.2014567- 584614 5703.8- 58 47 01-35 -39,-31 780 2.6/10.3319.84 - 0.2015030-5821 15 03 03.0- -58 21 35-9 -14,-9 0.4 0.7/12.3 4,9320.23一0.2815061-5814 1505 59.3 -58 14 03-63,-59 24 4.5/8.6320.23- 0.2915061-5814 15 06 00.5 - -58 14 14320.12-0.50 15061-5828 150606.1 - -58 28 44-11 -12,-9 4.6 0.9/12.2321.03-0.505122-5801 151202.6 - 58 00 50-63,-60 90.2 4.4/8.8321.06- 0.5215122-5801 151216.6 -5801 1227 4.4/8.8321.14- 0.53151250.9 -57 59 06-67.-61321.15- 0.5315 1255.3 - -57 58 51-664.7/8.5中国煤化工MYHCNMHG54Y. Xu,X. W. Zheng& D. R. JiangTable 1 (continued)SourceIRASR.A. (1950) DEC (1950) Vpak.Speak DRef.Name(°' ") (kms-1) (kms-1) (jy) (kpc)321.71+ 1.17 [5100- 5613150958.6 -5614 194.322. 16+ 0.63151446.8 -56 27 34322.16+ 0.641514 45.7.-63323.46-0.08 + 15254-5621 15 25 27.7323.74-0.26 15278- 562015 2752.0-56 2040324.70+ 0.331531 03.4-55 18 32324.72 + 0.341531 07.2324.92-0.56 15360-5554 15 3602.0326.47 +0.6915394-5358 15 3928.4326.64 + 0.60 15408 - 5356 ;154045.869.9 3.0/11.2326.66+ 0.5915408- 5356-43327.12+0.51 15437-5343 15 4344.3-5343264,9327.12+0.51 15437-5343 15 4341.8327.29- 0.58 .327.40+0.44 15454-5335 15 4530.4-533610-374,328.25-0.53 15541-5349 155407.6-534925328.81+0.63 15520 -5234 15 52 00.3-5234 22328.96+0.57 15530- -523115 5301.2. -523146320.46+0.48 15557-5215 15 55 54.2.-521612 .329.46+0.51 15557-5215 15 5547.9-521518-72330.07+1.05 15565-5126 15 56 31.8-51 2641.329.03- 0.2115 5642.0-5304 22329.03- 0.2015 56 40.6 .-53 0358329.31+0.15 15567-5236 155643.5- -5236 19-106-107,-10510.57.8/9.69329.18-0.31155755.5 -5303 26.-56329.18 -0.3215 5756.3-530327329.60+0.10 15584-5230 1558 17.429.7 4.0/10.7329.40-0.46 15596-5301 15 59 40.8-530113-67329.40-0.46 15596- 530115 5941.1-530133332.29+2.26 16019- -49031602 03.2-490414 .08.8 1.9/13.1330.95-0.19 16060-5146 16 0604.7-514711- -88330.96-0.18 16060-5146 16 0605.0-51 4644330.88-0.38 16065-5158 16 06 34.0-515900-73; 0.8 4.7/10.2 4,331.13-0.24 16071-5142 16 07 10.6-514233331.13-0.24 16071-5142 1607 10.8-514229-9128331.28-0.19 16076-5134 16 07 38.1-513412207 5.0/10.0 4,9331.54- 0.0716 082.7-511810-84331.52 - 0.101608 23.2.-51 2045331.45-0.19 16084-5127 16 08 24.8-512715331.34- 0.34 16085- -5138 16 08 35.8-513816331.34-0.35 16085-5138 16 0837.4-513832331.56-0.12 16086-519 1608 40.6-511959-104 -105,-94 47 6.5/8.4 4,332.96+0.77 16112-4943 1611 16.9-494308-513.6/11.5332.54-0.13 16132-5039 1613 14.8-503946332.65-0.62 16158- -5055 16 1554.4-5056203.5/11.6333.16-0.10 16159 -5012 16 1555.45.8/9.4333.20 - 0.08161600.1-5010085.1/10.033.23 - 0.06161604.9-813.8 5.1/10.1 .332.72- 0.621616 14.2-505318-465.4 3.3/11.8333.07- 0.45161702.4-5031 22333.12-0.43 16172- 5028 1617 12.3-502840333.13 - 0.441617 15.5-50 28471617 16.7-502745333.45 - 0.181617 32.3 - -50 0408. -43,-41 85 3.1/12.1中国煤化工MHCNMHGi.1.Statistical Properties of 6.7 GHz Methanol Maser Sources55Table 1 (continued)SourceIRASRA. (1950) DEC (1950)，Vveak... Veagr、 Speak D、Ref.Name(" (kms~4) (kms~)(jy) (kpe333.47-0.17 16175 - 500216 1734.7 - 50 02 4542 -49,-360 3.1/12.1 4,9335.73 + 0. 1916 25 46.0- 4811234 3.3/12.2335.79+ 0.17162606.0-48002267 3.6/11.9335.59-0.29 16272-48371627 15.4 -48 37 20110 3.5/120 4,9335.55 - 0.311627 11.3 - 483928 ;-116 119,-1123 6.9/8.63.7/11.835.61- 0.31162727.8- -48 37 03336.36-0.14 16297-4757162947.9 -47 57 28-744.8/10.8 .336.36-0.15 16297- 4757162950.9 - -47 57 46.21 4.8/10.8336.41 - 0.26-85.65.3/10.3 .336.43-0.26 16306-4758 :1631 00.1-93-77,-75336.83+ 0.0232 5.0/10.7336.86- 0.01 16313- 47291631 00.6- 47 30 20-77-82,-6816 5.0/10.71631 11.2 -47 2939350 29/17336.02 - 0.82 16313- 4840T68 224- 48 400-55,-394103.9/117336.99-0.03 16318-47241631 51.9 -47 2503-126 -127,-116 38 7.6/8.1337.00- 0.01631 50.6 _ 4724 292628336.83- 0.:163244.0--474623- -22 41.5 2.2/13.5337.62- 0.06 16344- 46581634 29.4 - 46 58 57;-321 3.3/12.4 4,9338.28 + 0.541634 29.8 - 46 05 00;-54.1/11.7337.63 - 0.081634 38.7 -46 58 53337.71 -0.0616348- 46541634 49.6- 46 54 43338.00 + 0.13163509.8- 46 3412-32 -36,-3142.7/13.0337.40-0.41 16351-4722163509.9 -47 22 22-39.5.337.41 - 0.4116351- 4722163509.8 -47 22 07338.08+0.02 16359-4635163558.81635 58.2-463528338.47 + 0.291636 18.6.-46 0635338.47+ 0.29163619.2 - -46 06503g1055163654.8 -4536 14-62338.44+006163711.646172338.43+0.05 16371-46171637 12.0_ 461749337.92- 0.4816 37 29,7337.92-0.46 16374- 470116 37 25.047 3.1/12.7338.93 + 0.3916376 - 45421637 39.5 - 45 42 380.68 2.4/13.5338.46- 0.25 16381- 46291638 36.1-4628383 3.8/12.0 4,916 3836.5- 4628372 3.8/12.0338.87- 0.081639 28.7- 46 03 389 3.3/12.5338.88- 0.081639 29.4 - 46 03 0514 3.3/12.5338.93 - 0.061639 36.5 - 46 00 052 3.4/12.5339.62-0.12 16424-45311642 26.5- 4531 1883 3.1/12.84339.62-0.13-4531433.1/12.8340.25 - 0.0516445-4459340.05-0.24 16445 - 4516340.06- 0.2516445 - 45161644 36.9 - 45 16 271 4.4/11.624079-010164532.7 -45 31 24-91 - 105,-885.6/10.3339.68- 1.21 16474 -4610164725.0 - 46 105926298339.68- 1.2116474 -461016 47 26.2_ 4611 12341.27+ 0.071647 40.3。 4408 38341.28 + 0.061647 43.9- 44 08 41.5 5.1/11.0339.88- 1.26 16184- 4603164824.8 -46 03 34，-27 1820 3.3/12.7 4,9341.22- 0.211648 42.1- -4421 53-3867 3.3/12.8342.38+0.10 16513-4316A 165123.6 -43 1651-91 -92,-885.8/10.4342.36+0.10 16513-4316A 165123.6 - -43 16510.4 3.7/12.5342.36+0.10 16513- -43164 1651 23.6- -43 16 513 -16,-2 0.7 0.8/15.4-400946-18-21345.01+ 1.80 16533- 4009165318.9- 40 09 293 -15,-10 31 1.7/14.7 .中国煤化工YHCNMH G自过i56Y. Xu, x. w. Zheng& D. R. JiangTable 1 (continued)SourceIRAS(1950) DEC (1950)Ypeak,DRef.danie(kpe)343.93 + 0.12165639.1 - 42 02 58+11,+15343.91+0.11 16566- 420416 56 38.7-42025814344.41 + 0.0516 58 34.0-41 4315344.42+ 0.05 16586- 414216 5837.1-41 4236-41 3736344.22-0.57 17006- 4215170033.8- 42 14 35344.23-0.57 17006-4215 17 0035.0 -42 1429-20 -33,-16 118 2.3/14.0 4,9345.51 +0.3517008-4040 17 0054.2- 40 40 18-18-23-1117423/143 49345.00- 0E 17016- 4 T120306”_403702.-10-13-8 1.6346.48+ 0.1312045417346.48+0.1317 04 55.0-4001 40346.52 + 0.12170505.5- 40 0015-2,00.9 0.3/16.2346.52 + 0.0917052 - 4001170513.4- 4001 25345.41- 0.9517059-413217 0604.9 -41 32 04-15 -19,-13 2.8 2.0/14.5 4,9347.58+ 0.2117079-3905 17 0759.5- 39 0558-103 -104,-95 2.7 6.5/10.1 4,9347.63 + 0.2117 08 09.6- 39 03 36-92 -93,- -89 11.5 6.2/10.4347.63 + 0.1517 0823.9- -39 05 50. - -97,-91 14 6.4/10.2347.63+ 0.1517 0824.8 - 39 06 00-97 -98,-96 18 6.4/10.2347.82 + 0.0217 0932.1- 3901 175 -26,-23 3.4 3.2/13.4347.91+ 0.0517096-3856 17 0939.4 .17 0939.1-385916-38 5602347.87 + 0.01170941.7- -38 59 13348.89 + 0.0917 1227.6 -38 065017 12858.4- 37 56205.9/10.8349.07- 0.0217 1325.5- -38 02 07349.10+ 0.1117 13 00.5--375619348.89- 0.1917136- 381617 1337.2-38 16 16350.02+0.43 17143-3700 17 14 23.8-36 5953350.01+0.43 17143-3700 17 1422.4 -37 0018.-1231 -37,-291.9/14.7,9348.24-0.98 17149-3916 17 1456.4 -39 16 02348.55-0.97 17158-3901 171551.1 - 39 0029-23.-9 40.5 2.1/14.6348.55-0.98 17158- -3901 17 1553.0- -39 00 532./14.6.9350.10+0.09 17160 -370717 1602.9 -37 0748-74 -76.-60 41 6.0/10.7 4,9351.16+0.70 17165- -355417 1636.5 - 35 54 39-5350.34+0.10 17166- -3656 17 1639.1 -36 55587,-61 26.9 5.8/10.9-66 -67,-56 12 5.8/10.9348.70- 1.04.17 1637.1-8-17,-3 60 0.6/16.1351.42 + 0.65 17175-3544 17 1732.4- 35 44 043300351.44 + 0.66171733.6 - 35 4211. -3 -14,+1 16 0.7/16.185208+01617200-3658 172008.2 -36 58 54-16,-13 31.3 2.5/14.3352.11+0.17172128.2612.-70,-64 2.3 6.2/10.7351.58- 0.3517220- 360917 2202.5-360951.17 22 03.2-3610096368/100351.78- 0.5417233- 3606 17 23 20.7-360645353.46+ 0.5617234- -340517 2333.2- -34 05 53-503 5.9/i1.0 49353.45 + 0.5417 2335.7- -34 0654352.51 -0.1517238-3516 17 23 48.5-351713-54,-49 6.5 5.7/11.2352.52-0.16 17238- -3516 17 23 51.4-3517 00-54,-49 6.3 5.7/11.2 4,9352.60-0.18 17242 -3513 17 2412.2-351337-96,-801.7 7.0/9.9352.12- 0.9317258- 3602 1725 55.7-360220-18,-7 20.1 2.5/14.3353.22-0.24 17260- -3445172605.6-34 45 06-160.4 3.4/13.5354.62+0.47 17269- -331217 26 59.8-3311 34-23 -27.-13 216 4.6/12.3 49353.41 - 0.3617271-3439 17 27 06.6 - -34 36 30-20352.63- 1.0717278- 3541 17 27 52.4 -35 4L 57-3 -7,7 180 0.9/16.0中国煤化工FHCNMHaB t57Statistical Properties of 6.7 GHz Methanol Maser SourcesTable 1 (continued)SourceIRASR.A. (1950) DEC (1950) Vpeak. VrangSponk DRe[.Name(hm") (°1")(kms-~1) (kms-')(jy) (kpe352.64- 1.09 17278- 3541172758.8-8,7 143.2 0.9/16.04 +92,+103 18+91,+95 21.0355.34+0.15 17302 -3245 173012.2- -32 45 5620+5,+21 9.8356.66- 0.27 17352- 315317 3514.2 -31 53 07356.66- 0.27 17352-3153 17 35 15.4- -35 53 179.6 2.4/146350.14+ 0.0317402- 2938 174014.2 .-2938034.8/12.2 4,9358.38- 0.4817403- 3032 17 4022.3 _ 30 32 35358.38- 0.48 17403-3032 17 4022.3- 30 32 3525.0 21.2359.44- 0.10174129.1 -29 2659-52.026.8 8.2/8.810359.44 - 0.10174129.1 -29 26 59-52” 8.2/8.8359.61- 0.217 4227.2- 29 22 18359.62- 0.24174227.8 _ -2921 5822.5 +14,+27 88.700.50+ 0.1817429-2823 17 4255.1 - 28 23 563.0/14.00.21 - 0.0049.20.22 - 0.0117430 -284450.53+0.18 .17430- -28221743 00.00.53 + 0.1817430-2822 17 43 00.0 - 28 22 22).4 5.2/11.8 917430-2822 17 43 00.0 - 28 22220.38 + 0.0417432-2835 17 4311.3- -2834 3728.70.81 + 0.1817436-2807 17 434.5. -28 06310.84+ 0.1817 13451.州08263..0.83+ 0.1917436- -280617 43 41.0-2806314.0.84 + 0.1917436-2806 17 4342.3- 28 06 240.30一0.2017439 - -2845 17 4357.7- -28 45 5529.5 8.0/9.00.31 - 0.2017439-2845 17 43 58.2 -2845 151388.0/9.0 9, 100.60- 0.0517440- 2825 17 4404.8- 28 25 4949.5; 8.2/8.80.64 - 0.0417440 -28231744 08.9- 28 23 29498.1/8.6 4,9,100.66- 0.0370.40.66-0.04- -28223352.03.0359.97-0.46 17441-2910 174409.8 -2910 590.65- 0.061744 13.8. -2823 41.51.0 +49,+52 3.4 8.3/8.70.65 - 0.05174411.4 - 28 23 2248.0 +46,+49 31.7 8.3/8.717 4411.0- 28 23 234833 8.3/8.707- 00317A1- 387 1 u- 258 OS8.282/880.67- 0.0317441-2822 174409.8 - 28 22 05o_ -28214069.20.67 - 0.0417441- 2822 17 4412.0 - 28 22 0260.40.68 - 0.0317441-2822 1744 11.1 - -28 21 1273.44.4 8.2/8.80.69- 0.0417443- -2821 1744 14.7- 28 20 5268.6328.2/8.8 4,90.70-0.04 17443-2821 1744 16.2 - 28 20 3068.51.13-0.11 17455-2800 17 4532.3- -28 00 432.610.0358.26- 2.0517463- -3128 1746213- 31 28 205.358.27- 2.08 17463-3128 174627.0- 31 28 3816.70.55-0.8517470- 2853-2853391468 7.5/9.5 4.92.14+ 0.01.2.61+ 0.1317480- - 2636 17 48 04.7- 26 36 57.52 2.0/15.02.55 + 0.1817480- 263617 4744.4 - 26 38 5263.7 2.0/15.0391 +0.0017 5133.1- 2534 166.55- 0.10157-201157869-2026.55-0.1017577- 2320 1757469. 220196.78- 0.27_2 135+14.+306.79 - 0.2617589-2312 175854.7-23 12 3926.9 +15, +308.14十0.2317599- 2148 17 59 59.9_ 21 48 1220+18,+228.13. + 0.2217599 -2148 18 0001.2- 21 4911+19, +214.6 4.29中国煤化工fHCNMHG58Y. Xu, x. w. Zheng & D. R. JiangTable 1 (continued)SourcIRASRA. (1950) DEC (1950)Vrange、Speak. DRef.Name(hm")(km6-1) (kmB-1) (Jy) (kpc)10.10+0.7518021 - 1950180212.0 - -19 50 520.4 0.4/16.38.67- 0.35.18032 - 2137180314.8 -21 37548.67- 0.365.6 4.8/11.9180322.8 -21 872448 4.8/11.98.68 - 0.3718032 - - 2032180314.7 -2032089.62+ 0.2018032- 2032 .1803 16.0 - 2031 53-4,+9 509016.59.99- 0.0318048- 2019 .18 04 53.1-20190447 +40, +52289.98 - 0.0418048 - 20191804 55.0 - 20 19 58+40,+48 35.4 5.0/11.810.48 + 0.0318056- 195218 05 39.71951 5255 +58, +66 1610.47 + 0.0318056 - 195218 05 38.7-19523473.4 +70, +75.818 05 40.0- 195224314,10.44 + 0.0118056 - 195418 0541.3 - 19 54 2516.5 5.9/10.810.45- 0.02180547.0- 19 55 0173.2 +68,+79 25 5.9/10.810.30- 0.1518060 - 2005180557.9 - -20 06 2610.6 +4, +186.0910.31- 0.1518060- 200518 0600.3- -20 05571110.33- 0.17180606.7 . -20 0534+4,+17108.7 1.9/14.810.88 + 0.1318061- 1927180609.6 -1927 5616.8 +14.+18 4.5 2.6/14.110.32 - 0.2618064 - 2008180626.0 - 2008 4239.0 +9, +40.4.5/12.210.96 + 0.0118067- 192718 0644.2 - 19 2735+23,+26 20.210.96 + 0.0218067-.192723.9 +23.+253.3/13.4 .10.96+ 0.022518 3.3/13.418 0642.4 - 19 220320 +15,+21 0.7 2.9/13.810.62- 0.3218072- 195418 0716.2-1954 4918.918 0721.4.1963918.9.10.63-0.38 18075- 195618 0731.012.89+ 0.4918089- 173218 08 56.412.89+ 0.4918089 - 173238.9614.1/12.512.03- 0.03 18090- 183218 0906.382 6.7/10.012.03-0.03 18090- 18321809 05.7- 1832 42107.4 +105,+112 77 6.7/10.011.91- 0.11180908.0 - 1841 1536 +33,+37 2.6 4.0/12.611.90-0.14 18092- 1842180915.2- 18 422137 4.4/12.211.90- 0.141809 13.742.6 +39,+4419 4.4/12.211.94-0.15 18094 184018 0920.3 - 18405148 +45.+49 2.3 4.7/11.911.95- 0.1618094- .184046.8 +46,+49 2.312.25- 0.05 18096- .1821180937.2.212.21-0.10 18097- 1825A 180944.0 - 18 25 0920+19,+214,912.20- 0.1118097- - 1825A 18 0944.1-1825361718 0946.4263.5 3.3/13.412.22- 0.1118097-18257.9 2.6/14.011.99-0.28 18099 -1841180955.6 - 18 41 32601.8 5.2/11.411.99-0.28 18099- 184160.212.63- 0.0218102- 1800181016.7 - 18 002624.02.9/13.6512.63-0.02 18102- 180011080157.7， 5.0/6818108 -17597.75.0/11.8 .12.68- 0.18181059.811.94- 0.6218 1104.1323.8/12.94,5,912.93- 0.0818111- 17461811 07.013.18 + 0.05 18111- 17291811 10.148.512.91- 0.26 18117- 175318 11 43.8-1753043912.91- 0.26 18117- 1751811 43.7 -17 53 0139.824213.71- 0.0818126- 1705181241.1 -17 053351.9 +42,+52 3.4 4.6/11.914.10+ 0.09 18128- 1640181251.1 -16395315.3+5,+16.20014.10+ 0.09 18128- 1640 .181251.8 -16 40 0115.111.50-1.49 18134-1942181324.6 - 19 42 257 +5,+17 1601.1/1.511.51- 1.5018134- 1942181328.3 - 194225+6.+17 247.7 1.1/15.5 .11.51- 1.50 18134- 1942181328.3-19422516 1.1/15.514.44- 0.06 18141- 16261814 06.2 -16 26 3127.0 +26, +283.0 3.0/13.4中国煤化工YHCNMHalk. lStatistical Propertics of 6.7 GHz Methanol Maser Sources59Table 1 (continued)SourceIRASR.A. (1950) DEC (1950) Vpeak Vang、 Speak D、DRef.Namekms"' )14.61+0.01 18141-1615 18 14 09.0-16 154723+19,+35 2.3 2.8/13.691461+0.01 141-1616 18 1000-1615474.8 +22,+28 2.9 2.8/13.613.66-0.60 18144-1723 18 1429.8-17 23235L0 +47.+52 33 4.42018.34+1.77 18151-1208 18 1509.0-12 083328.2 +27,+29 T2 2.6/13.53318.34+ 1.7718151-1208 1815 09.0-1208 3327.7 +27,+29 65 2.6/13.5318.33+1.76 18151-1208 18 15 10.3-12 08 60+27,+29 46.1 2.6/13.5315.08-0.12 18155-1554 18 1534.8-1554 50.45.8 +45,+46 3.14.2/12.3 514.33 - 0.6418159- 1648 18 1559.6-1648 5521.15.03-0.68 18174-1612 18 1731.6-16 13 024;15.03-0.67 18174-1612 181729.3-1612 480.9 +20,+23 192.51815.66-0.50 18181-1534181806.7-15 34 3616.59-0.05 18182-1433 18 18 18.5-1433 16+52,+69 21 4.7/11.6 4,16.58- 0.0518182-1433 1818 16.8二14 81961.6+56,+69 244.7/11.616.36-0.21 18184-1449 181825.6-14 112690.8 +90,+91 1.35.8/10.590.817.64+0.16 18196- 133118 19 36.5.- 1331 3817.64+0.15 18196-1331 181937.3-1331 45+212:2.01117.64+0.15 18196- . 1331 18 19 37.3._ 1331 452018.07+0.0818207-1311 18 20 42.5-1311 0155+2012118.16+0.10 18208- 1306 18 20 50.0-1306 0157.9 +55,+5918.46-0.01 18217- 125218 2147.5--12525349 +47, +5018.46- 0.01 18217- 1252182147.5 -12 52 5349.2 +48, +5012.1618.46-0.01 18217- 125218 2148.5-12 525118.66+0.03 18220-1241 18 22 02.5-12410080.2 +76,+83 22 5.3/10.818.88+0.05 18224- 122818 22 24.2-12285438.2 +38,+39 3.18.27-0.29 18224-1311 18227.1 -1311 1675.2 +73,+80 1:19.47 + 0.171823 07.3-1154 3018+13, +2719.49+0.15 18232-1154 18 23 12.7-11 54 1621 +20,+27 19.3 2.1/13.9 4,19.49 + 0.1418232-1154 182315.2 - -11 54 2220.7 +18,+25 15 2./13.918.84- 0.3018236-1241 1823 36.041.1 +41,+44 2.3 3.5/12.6318236-1241 18 2336.0-12 05 3642.0 +39,+45 5 3.5/12.6319.36-0.02 18236- 1205 18 23 36.326.3 +24,+29 6.7 2.52019.36-0.02 18236- -120518 23 36.32719.61-0.121824 26.6-1155183.6 4.11919.61-0.14 18244-1155 18 24 29.5-11 55 3957 +50,+61 18 4.3/11.7 4,919.61- 0.1318244-1155 18 2428.2-11 55 3856.3 +48,+58 8.6 4.3/11.719.62-0.23 18248-1158 18 2449.7-1157 5236 +36,+43 0.4 4.0164,20.23+ 0.07 18249-1116 1824 56.9。-11 165972 +60,+78 100 11.1619.20-027。_115436714 +68,+76 9421443.620.08- 0.1418253- 113018 25 23.3_.1130442.9 3.6/12.4.19.88- 0.5318264- 1152 18 26 26.6-11 52216.87- 2.1618265- 151718 26 32.5+15.+1916.87- 2.16 18265- -151718 26 32.915 175114.6 +14,+19 .17.02- 2.4018277-1517 18 27 43.4-15 164524.1 +20, +25.17.01-2.40 18277- - 15171827 42.1-15 17 1723.3 +19,+24 3.21.56- 0.0318278- 1009 18 2749.6-100919116.6 +115,+119 15.72022.04 + 0.2218278- -0936 18 2750.0-09 38 5353.4 +46,+54 5.5 3.9/11.821.88+ 0.0118282-0951 18 2816.6-0951 1020.4 +20,+22 2.9 1.9/13.821.88+0.01 18282 -0951 1828 16.6-09511021 +17,+22. 15. 19/13.8 4,22.35+ 0.0518290-0924 18 29 01.0-0925 15+79,+81 21.1 5.1/10.618290- -0924182901.0-09 251580 +77,+88 13 5.1/10.6 922.35+0.05 18290-0924 18 29 01.0-09251580 +79,+85 12 5.1/10.822.43-0.161829 57.5-09 264129 +22.+40 20 2.5/13.222.43-0.23 18302- -0928 18 30 12.4-09284629.0 +28,+39 3.22.5/13.223.39+0.19 18305 -0826 18 30 30.4-08261874.1 +71.+77 17 4.8/10.823.81 + 0.39 18305-0758 18 3035.0 -07 58 0076.4 +74,+78 9.6 4.9/10.6中国煤化工MHCN MH alhd i30Y. Xu, X. w. Zheng & D. R. JiangTable 1 (continued)SourceRASR.A. (1950) DEC (1950) Vrak、, Vrnangy、Speak. DNarme23.46 + 0.0718310-0825 1831 03.6 -08 25 5687.4 +81,+89 12 5.3/10.323.46+ 0.07 18310-0825 1831 03.6-082556+82,+925.3/10.323.46+0.07 18310-0825 18 3103.6-08 25 5688.4 +85,+90 6 5.3/10.323.47 +0.0518310 -08251831 08.2-08 25 40+86, +8911.3 5.3/10.3325.65+1.05 18316-0602 1831 40.0 .-060223+40, +43113.3 3.31525.65+1.05 18316-0602 183138.9-06020841.8 +41.+42181 3.38825.65+1.05 18316- 0602 1831 40.0 - 06 02 2341.9 +38,+44 178 3.31525.65+1.05 18316- 0602 1831 40.024.18- 2.5318317- .0859- -08594123.25- 0.2418317-0845 1831 45.9-08454718317-0845 183145.9-08 45474.3/11.318317- -08451831 46.3-08453923.01 - 0.4118 31 55.6-09 03 0975 +69,+84 405 4.9/10.823.44- 0.1818319-0834 18 31 55.3-08 3401103 +94,+113 779.0-23.44-0.18 18319-0834 1831 55.3-0834 0102.6 +95, +108 40:2/10.5_08433618321- 0820 18 32 08.5.--0820424.54+ 0.3118322-0721832 13.5.23.19- 0.5018324-0855 18 32 26.4-08 55 0275.2 +73,+83 9.23.70-0.19 18324- 082018 32 27.3-08 20 2380.0 +75,+81 30 4.9/10.6-08 202379.0 +75, +859.2 4.9/10.6323.70- 0.1918324-0820 18 3227.378 +58,+81 26 4.9/10.6324.33 + 0.1518324-0737 1832 35.2-073733.109.9 +107,+120 4.6 6.5/9.024.49 - 0.0418334-0733 1833 23.3 - -07 33 50+113,+116 33.1 6.6/8.9824.49- 0.0418334-0733 18 33 23.3-07 3350115.2 +114,+116 29 6.6/8.9318334- 073318 33 23.3.-0733 50114.4 +108,+116 29 6.6/8.9324.79+ 0.08183329.9-071445114 +105,+115 82 6.8/8.724.81+0.1018335- -0713 1833 30.1-07 1310113.0 +106,+115 9724.85+0.09-07113322.92+ 0.08-070746109.3 +107,+11824.68- 0.1618341 -07271834 09.3-07 2723114.0 +113,+115 16 6.6/8.9324.68 - 0.1618341 -072718 3409.3--072723118.1 +111,+114 3.5 6.6/8.9325.41 + 0.1018345-0641 18 84 36.9-0641 1594.7 +93,+100 8.0 5.7/9.625.41+0.10 18345- -064118 3436.92670+00818353-0628 18 3523.8- -0628 0726.65+0.0218372 - -0537 18 37 12.4. . -053755107.1+106.+108 5.26.61- 0.2118379- 0546 183757.4-0546 11104.2 +103. +116 9-05 4611103.2 +102,+115 126.61- 0.2218379- 0546 18 37 58.2-05 4628+102,+105 10.06.1/9.1327.30+ 0.1518379- -050018 37 55.5-05 003434.9 +34, +3718379-0500 18 37 55.5--05003434.9 +34, +367.81027.36- 0.1618391-0504 18 3911.0--05044399.7 +91,+102 2:6.1/9.0-050443100 +88,+104 2:27.79+ 0.04 18392-0436 18 39 15.8-0436 0911.8 +108,+113 1.28.15+ 0.00184002.2-0428 16101 +92,+105 34 6.0/9.028.40+0.07 18402-0403 18 4016.5- -04 031471.1 +67,+81 3.4 4.6/10.428.20-0.05 18403 -041718 40 19.3-04 1702100.8 +94, +10456 6.2/8.728.20- 0.0518403--0417 184019.3 . _-041702.99 +94,+102 3.3 6.2/8.728.86+0.07 18411-0338 1841 07.9.-0338 3610528.29-0.38 18416 -0420 1841 39.8-04210081.5 +81, +845.0/10.0328.29-0.38 18416-0420 18 4139.828.29-0.38 18416-0420 18 41 39.880.7 +79,+93 62 5.0/10.03 .28.31- 0.4018416-0420 1841 45.8-04 2052+80,+84 58.6 5.0/10.0328.84 - 0.23 18421-0348 18 42 09.5-03 475800 +99, +104 1.3 6.316中国煤化工YHCNMHGStatistical Properties of 6.7 GHz Methanol Maser Sources61Table 1 (continued)SourceIRASR.A. (1950) DEC (1950) VpealVrangeSpeak D、Hef.Name(hm") (0" (ki"I) (kms=~') (Jy) (kpe28.83- 0.2418421- -0348 1842 11.3.-03 483783.9+81,+93 586.31628.83- 0.2518421-0348 18 42 13.1-03490183 +79,+94 7329.86- 0.051843229-024826101 +99, +105 67 6.5/8.229.94- 0.0218434-0242 184325.6 -02 43 22100.429.95-0.0218434- -0242 184326.7- -02 42 3896 +95.+102 206 9.091,929.98 - 0.0418 4334.9-02 42 19104 +97.+105 1430.30 + 0.0618438-0222 18 4348.9 -02 222830.82 + 0.2718440-0148 1844 00.6 -01 48413104.9 +104,+111 3.08.216,918440- -0148 18 44 00.6-0 130.76+ 0.2118441-0153 1844 08.4-01 534218441- -0153 1844 08.4-01 5342.5.6/9.031.05+ 0.3518441-0134 184408.8- -01 34 1280.8 +78,+84 4.5.2/9.430.79 + 0.2018 4412.3-0152 045.5/9.130.23- 0.1318443-0231 18 44 21.7-023112108.1 +100.+114 186.0/8.730.54 + 0.0218443-0210 18 44 23.9-02 104430.20 - 0.17184425.8)8 +101,.+111 18.7 7.1/7.630.22 - 0.18184431.3 -02 32 50113 +111,+115 11.730.86 + 0.12 .18446-0150 18 44 38.1-01 5033102 +37,+108 2.4 7.6/9.1930.91 + 0.14 .18446-0150 1844 38.2 -01 47 34+98, +11153.6 7.6/9.1930.58- 0.0418446- -0200184441.2 -02 09 4230.59- 0.0418446 -020918 4442.5-02 09 434101 +91,+110 1830.82- 0.05.6.9/7.731.07+0.08 18452 -0141. -01404131.07+0.05 18452-0141-0141355,930.87- 0.10 18454-0156 184526.6 - 01 5608 101.1 +101, +1084.331.16+0.04 18454-0136 18 4528.1 -01 36 4631.28+0.06 18456- 0129 184537.2-01 4903110.0 +102,+113 7131.28+0.06 18456- -0129 18 4537.231.58+ 0.0818461- .0113 1846 06.8-01 133832.03 + 0.0518470- -0050 18 47 01.9.- 00502192.832.11 + 0.9918470- -0044 18 47 02.1-00443593.2 +91, +10518470- -0049 18 47 03.8-004859+91, +102 103.632.74- 0.0818487-0015 18 48 47.8-0015 5038.232.74 - 0.0839+24,+45 47 2.0/12.01832.99 + 0.0418488+0000 18 48 51.100004192.6 +90, +9421 6.0/8.3318488+000 18 48 51.191.7+89, +9327 6.0/8.3332.99 + 0.0318488+0000 18 48 54.100 00 36+89,+93 16.3 6.0/8.333.09- 0.0718494+0002 18 49 25.L000251104.6 +95, +1061933.09- 0.0718494+000218 49 25.100 025196 +95, +106 305.7/8.533.13-0.09 18496+0004 18 49 33.600 042573.5 +72, +75133.13- 0.0918496+0004 18 49 33.60004 25+71,+81 12.4 7.11633.42- 0.0018497+0022 18 49 47.00022 07105.0 +100,+108 26 9.51600 2207105.0 +96, +107 209.51634.25 + 0.1518507+0110 18 50 46.801 110657.9 +55, +63183.81618507+0110 18 5047.001 1049+58, +622934.40+0.2318507+0121 18 5045.20121 0955.8 +55, +63213.61534.39+0.2118507+0121 18 5048.5011948+64 18.5 3.61534.24+0.13 .1850 49.00L095755.5 +55,+62 20 3.8/10.334.00 - 0.0118508+0052 18 50 52.700524059.0 +58,+63 3.9 4.0/10.133.70-0.26 18512+0029 18 5113.0002945.35.02 + 0.35 18515+0157 1851 29.00157 2935.02 + 0.3518515+0157 18 5129.001 572937.43+1.5218517+0437 1851 45.3012749+40,+52 298 2.9/10.636.12+ 0.5518527+0301 18 52 46.20301 13910+0+827920/80.5.0/8.7中国煤化工FYHCNMH G32Y. Xu, X. w. Zheng& D. R. JiangTable 1 (continued)SourceIRASRA. (1950) DEC (1950) Vpeak ..Sook DRefNauneNamekis-) (kmg-1) (Jy) (kpe)35.20- 0.7418556+0136 18 55 41.101 36 2626, +3525 2.1/11.818289+24 2. 1/11.81835.20- 0.74 18556+0136 18 55 41.16.3/7.2337.55 + 0.2018566+ 0408140904 080383.737.55 + 0.2018572 + 0057.185714.90057 38.18572+ 0057 18 57 16.200 57 21礼80-118572+00570057 2146.937.54- 0.1118577+0358 18 57 46.50358 5262.6 +49,+63 5.18592+0108 18 59 13.101 09 0735.20- 1.7418592+0108 18 5914.501 08 4642.6 +40,+47 595 3.01638.12- 0.2218592+0426 18 5914.304 26 2469.4 +69,+71 2.4.9/8.540.42+ 0.7019002+0654 19 00 13.506 543715.6 +5,+16 1840.42 + 0.7019002+0654 190014.406 54 281.2/11.8 .38.93- 0.3719012+0505 19 0115.5050519.32.3 +31,+34 5.4 2.3/10.940.27- 0.2019031+0621 19 0309.80621 316.2/6.840.62- 0.1419035+0641 19 03 34.60641 5731.0 +30,+36 1510.5631 +30,+3717 10.51041.11- 0.2419048+0705 19 0451.107051763.4 +63,+64 3.7 4.7/8.141.23- 0.1919049+0712 1904 55.407124057.1 +55,+58 3.2 4.2/8.643.15+ 0.021907 47.009 003043.16 + 0.0219078+0901 19 0748.30901 189.1 +7,+22 3143.16+ 0.0219078+0901 19 07 48.343.17 + 0.0119078+0901 19 07 51.009 012120.0 +19,+22 12.43.17 - 0.0019078+0901 19 0752.609010443.80- 0.131000510020 1000207.09:30421 9095 +093009304243.18- 0.5219097+ 0847190944.8.08470945.07+ 0.1319110+ 1045 19 11 00.510454145.07 + 0.1319110+ 10451911 00.51045 415745.47+ 0.1319117+ 11071911 46.211 07 0345.47 + 0.1319117+1107 19 11 46.211 070365.8 +57,+67 109.51645.49 + 0.1319 1150.011 07 5357.213.4 4.9/7.045.44 + 0.0719 11 56.611 03441.9 4.0/8.043.89 - 0.7819120+0917 19 12 02.80917 1947.4+47.+5334 3.6/8.743.89- 0.7819120+0917 1912 03.109 17 389.8 3.6/8.745.46+ 0.0619120+1103 1912 00.4110359.56.1 +55,+66 4.145.47+ 0.0519120+1103 19 12 02.51104 3156 +55,+59 5.3 6.01849.41+0.33191864+1440 19 1839.714405850.01+0.5919189+1520 1918 55.01520 16.-5.0-10,-2 6.50.32 + 0.6819191+1538 19 1911.415 38 3720.9 +26,+33 2.8 2.5/8.449.57 - 0.2719211+1432 1921 10.462.8 +58,+66 2949.47 - 0.3719213+1424 1921 21.81921 20.61424 16B4 +60,+75 124049-03014250859.+51, +608549.59- 0.3919216+1429 1921 37.214 29525949.67- 0.4619220+ 1432 19 22 02.214 32 0749.05- 1.0919230+1341 19 23 06.9. 1341 4159.619230+1341 19 2306.91341 4i53.03 + 0.1219266+1745 19 26 40.117 454110.0 +9,+11 3.3 0.8/9.453.14 + 0.0719270+1750 19 27 03.917 50 0423.8 +23,+25 1.9 1.7/8.553.63十0.0219282+1814 19 28 14.7181432.18.7 +18.+19 6.3 1.6/8.552.67-1.09 19303+ 165119 3020.21651 04+64, +68 10.058.77+ 0.6519366+2301 19 36 40.12301 4234.0 +31,+3659.83+0.67 19388+2357 193852.6 23 57 3638.4 +36,+41 3159.84+ 0.6619388+2357 1938 55.92357 50.+37,+39 24.759.78+0.0619410+2336 19 41 03.623 365117.3 +14,+28 359.78+ 0.06 19410+2336 1941 03.623 36 5125 +14,+27 42 2.9/5.7中国煤化工MYHCNMHGiStatistical Properties of 6.7 GHz Methanol Maser Sources63Table 1 (cortinued)SourceIRASR.A. (1950) DEC (1950)SpeakNamneN ame60.57 - 0.1919437+2410 19 43 45.424 10 183.6 +3, +4.4.1 0.3/8.070.14 + 1.7319589+3320 19 58 57.03320 47-26.422 8.01619589+332019 58 57.033 20 47-26.5 -27,-26 9.8 8.01673.06 + 1.8020062+3550 20 06 17.13550 32- -2.835 50 32-2.510 5.7369.54 - 0.9820081+3122 20 0809.931 22 4215.1 0,+16 10971.53- 0.4020110+3321 20 11 05.1 .3321 1110.7 +3,+11 5.3 2.3/3.178.12+ 3.6320126+4104 20 1241.041 04 20-6.51 1.71675.77 + 0.3420198+3716 20 19 49.137 16 16-2.939 3.910 .79.75 + 0.9920290+4052 20 29 03.140 52 1680.87 + 0.4220350+4126 20 35 04.841 26 024.3 4.81-4.010 4.81899.92+ 1.5121074 +494921 07 28.449 49 4694.60- 1.8021381 + 5000 21 38 10.650 00 42-40.994.60- 1 .8021381 +5000 21 38 10.650 004298.04+ 1.4521413+5442 21 41 21.254 42 30108.19 + 5.5222272+6358 22 27 12.2635821. -10.9 -13,-9 91108.19+ 5.5222272+6358 2227 12.26358 21-11.3 -12,-10 109 0.916109.87+2.12 22543+6145 22 54 20.2.61 4555815 0.711109.92+ 1.98 22551+6139 22 5511.761 40 00-2.4430.63108.76- 0.9522566+5830 22 56 37.058 30 52-45.7.2.8 5.31411.54 + 0.7823116+6111 23 11 36.0611149.- -56.3296 2.81611.25 - 0.7723139+5939 23 13 58.359 3906- -38.5-42,-37 4.0 3.516References for sources and distances:l van der Waltet al. 1995. 2 van der Walt et al, 193 Slysl1 CasweI et al, 1995. 5 Szymczak et al, 2000.3. Slysh et, al, 1996 MacLeod et al., 1992. 7 Schutte etal, 1993. 8 Gaylard et al. 1993.9 Walshet al, 1997. 10 Caswellet al, 1996.11 Wuet al, 1996.12 Humphreys, 1978. 13 Eiroe et al, 1994.14 Wouterloot et al, 1993.15 Plletal, 19919 16 Larionov et al, 1999 17 Hughes & MacLeod, 1993.18 Baudryetal, 1997. 19 Jjinet al, 1999. 20 Molinari et al, 1996.(upper panel) encloses the region [25 - 12]> 0.57 and [60- 12] > 1.30, first defined by Woodand Churchwell (1989, hereater the WC criterion) and is often used to identify massive starsassociated with UC HII regions. Only about 13% (48/361) lie outside the box. Methanolmaser emission is believed to be associated with massive stars, and so the WC criterion receivesfurther support here. It is noteworthy that although the objects, taken as a whole, have a largespread in the color-color diagram, more than 70% (219/361) fall inside a very small region:0.57≤[25- 12]≤1.30 and 1.30≤[60- 12]≤2.50 (the central box). The distribution in thecolor-color diagram might indicate an evolutionary phase of star formation since the IRAS colorsare possibly related to the evolution of the 6.7 GHz methanol sources (MacLeod et al. 1998).Maser will not be excited if the radiation is too weak, and will be destroyed if the radiationbecomes too strong. In the earliest stage of star formation, the massive star is surrounded bycold and dark clouds with very red IRAS colors. The emision of dust from the crcusellardisk or envelope is too weak to produce the 6.7 GHz methanol maser ermission eficiently. Withthe appearance of an UC HII region, the emission of dust gets stronger and also the maser中国煤化工fHCNMH164Y. Xu, X. W. Zheng & D. R. Jiangemission. At that time, the radio continuum from the UC HII region is too small and/or weakto be detected (Walsh et al. 1998, 2001; De Buizer et al. 200; Lee et al. 2001; Minier et al.2001). As the UC HII evolving further, however, the masing gas cloud either warms up or isdestroyed by the expanding UC HII region. Therefore, the fact that the majority is located in asmall region in the color color diagram indicates that the 6.7 GHz methanol maser appears onlywithin a very short period during the earliest stage of star formation. The dotted line (lowerpanel) in the color-color plot is the best fit, which possibly indicates an evolutionary trend ofmaser frequency as one moves along this line from the top right corner (very red colors) to thebottom left corner (very blue colors).3.4 Velocity Range of Maser EnissionThe 6.7 GHz methanol maser emission has a large velocity dispersion ranging from lessthan 0.5 to 71 kms-', as shown in Fig. 3. The mean velocity range is about 8.2kms-l. Thisappears to be consistent with the result of Slysh et al. (1999). Apparently the velocity rangesbelong to two groups: one from 1 to 10 km s=1 (peaking at 5) one from about 11 to 20 kmg-1(peaking at 12). Nearly 62% (298/482) belong to the first group, and about 36% (138/482) tothe second group. Only a few objects are outside these two groups. Among the outsiders, threehave ranges greater than 30km s~ I (the largest one is 71 km s-1 for the source 18446 -0150).20一0 5101520253035 40Velocity range (km s~)Fig.3 Velocity range distribution of 6.7 GHz methanol masers. The .velocity range is less than 20km s~1 for most objects. A few haveranges greater than 30km s-1 , and the largest range is 71km8 1.The velocity range can be caused by dfferent masers with diferent radial velocities. The6.7 GHz methanol masers may sten from diferent diretions because masers can in principleoccur in either outAows or disks (Sobolev et al. 1997; Norris et al. 1993, 1998; Walsh et al.1998, 2001; De Buizer et al. 2000; Lee et al. 2001; Minier et al. 2000, 2001), and in generalthe velocity range can be very diferent for masers from outlows and disks. If the masers occurin the disk, then their vlocites will be close to the Keplerian veoitie,s and a small velocityrange will be expected; but if they occur in outflows then a larger velocity range will result sincethey may stem from diferent directions. When an outlowing wind strikes a denser material中国煤化工，CNMHGStatistical Properties of 6.7 GHz Methanol Maser Sources65a low-velocity maser may be produced, whereas if the wind strikes a less dense material ahigher-velocity maser will be expected. Therefore, there may exist a large velocity spread if the6.7 GHz methanol masers originate from outfows.An alternative explanation for the double-peak of the velocity range distribution could bethat the masers in the first group originate from circunstellar disks while the second groupcomes from outflows.For the first group, the Keplerian velocity of a maser is about 3 km s-1, assuming the massof the young star, ~ 10 Mo, and the maser at a distance of 1000 AU (SIlysh et al. 1999),To some extent, there are uncertainties in the distance and the mass, so the observed peak atabout twice this value can be considered as consistent with this interpretation.The 6.7 GHz methanol masers in the second group lie probably in outward-propagatingshocks. The gas within circumstellar envelopes heated by the central star will be at a muchhigher pressure than the surrounding cool gas, and will tend to expand. Since the expansionvelocity is likely to exceed the sound velocity in the surrounding gas region, a shock front maybe expected to form, moving out through the ambient gas. This is similar to the 'expandingshock' (Walshet al. 1998). The Keplerian velocity and the expansion velocity of masers mayeach be about a few km s-'; together, they could result in a range of about 10-20 kms-1 ormore, as is observed for the second group. The few objects with velocity ranges more than 30kms- 1 are likely to originate from high-velocity outAlows. For example, some maser componentsin W 75 may originate from a jet (Minier et al. 2001).3.5 Relations between Maser and Infrared Flux Densities, and between Maserand Infrared LuminositiesWe have investigated the relations between the 6.7 GHz methanol maser peak fAux densityand the IRAS fux densities in four IRAS bands for the 361 sources (Fig. 4). Except for a fewobjects, the maser Aux density is les than 20 percent of the 60 um fux density and less than 25，per cent of the 100 pum fAux density. This appears to be consitent with the resuts obtained byvan der Walt et al. (1995), Slysh et al. (999), and Szynczak & Kus (000)0. Some sigifcantcorrelations were found between the maser peak flux density and the 25, 60, and 100 pm fuxdensitie: the respective crrelation cefficients are 0.19 at 99.97% at confidence level, 0.23 at9.99%，and 0.22 at 99 99%. This means that the maser peak flux density increases with the 25,60, and 100 um Aux densities. This is inconsistent with the results of van der Walt et al. (1995)and Szymezak & Kus (2000) who found only weak or no crrelation between them. Althoughsome clear cases of correlation are found, the scatter in both axes is several decades, soit isunclear whether or not there is real physical connection between the them. No correlation wasfound between tthe maser peak flux demsity and the 12 pm flux density, in agreement with whatwas first noted by van der Walt et al. (1995).We plot the 6.7 GHz methanol maser luminosity against the correspondinginfrared lumi-nosity for 355 sources in Fig.5. The infrared luminosity is caleulated with the formula of Casoliet al. (1986). From the plot, we can see that the 6.7 GHz methanol luminosity increases withthe infared luminosity. The crrelation coficient is 0.34 at 9.99% confidence level,The infrdermisinmision is predominantly produced by crusellar dust that has been heatedby the central star, while the maser enision is produced by sorne chumps or inhomogneitisinside some crumstellar envelope or disk. Therefore, the infrared ermission originates from amuch larger region than does the maser emission. Now, the dust grain temperature decreases中国煤化工。YHCNMHCL166Y. Xu, X. W. Zheng & D. R. Jiang12 μm25 um0* t.资0' t0f1005 ro4 t60μm100μmo*f令1030o2F02 t00 to2030*05'IRAS flux densily (y)IRAS flux density (Jy)Fig.4 The 6.7 GHz maser peak fux density versus IRAS fux densities. Equality of the twois marked by the dashed line.1E-31E-3 1B-1E-6IE-IE-804!0LrR(Lg)Fig. 5 Methanol maser luminosity (LcHzOH) versus the associated infrared gource luminosity(LrIR). The correlation coefficient is 0.34 at confdence level 99.9%.中国煤化工MHCNMHG4tStatistical Properties of 6.7 GHz Methanol Maser Sources67radiation field and the decreased ability o[ the dust to absorb the increasingly longer wavelengthradiation. The radiation, at 12 pum, is generally attributed to emission from grains of the innercircumstellar envelope or disk (perhaps within the HII region), where the radiation is too strongto produce the 6.7 GHz methanol maser emission (either there is not enough methanol molecularto form the maser or the gas temperature so high as to quench the maser), while the radiationat 25 to 100 pum originates from a larger distance, where the conditions may be right for masing.On the other hand, the fact that in most of the methanol sources, the maser Aux density isless than 20 percent of the far-infrared flux densities suggeets that the far-infrared radiation isa possible Imnaser punp. This is also suggested by the fact that most of the stellar luminosityis attributed to the far- infrared radiation. For if this is true, then the maser intensity willdepend on the far-infrared flux densities, which has indeed been shown by the correlation tovarying degree between the maser peak fux density and the 25, 60, and 100 pμm fAux densities.These correlations, therefore, manifest that the maser emission is in fact associated with thefar-infrared emission from the dust at a larger distance from the star. In short, the 6.7 GHzmethanol masers most probably originate from outer molecular envelopes or disks.4 SUMMARYFrom a statistical study of all the known 6.7 GHz methanol maser sources, we obtain themajor findings as follows.(1) On the color color diagram, more than 70% objects fall within a very small region with0.57≤[25-12]≤1.30 and 1.30≤[60- 12] ≤2.50, suggesting that the 6.7 GHz methanolmaser emission may appear only during a limited period of massive star formation.(2) The velocity ranges of masers consist of two main groups: one from 1 to 10 km s-1, andone from about 11 to 20 km 8" -1, which indicates that the masers may be associated with bothdisks and outlows.(3) Some significant correlations are found between the maser and far-infrared flux densities,and between the maser and infrared luminosities: the maser peak fAux density is proportional tothe 25, 60, and 100 um fAux densities, respectively; and the maser luminosity increases with thefar-infrared lumninosity. 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