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Search and investigation of new stellar clusters using the data from huge stellar catalogues
Kop osov S.E. & Glushkova E.V., Zolotukhin I.Yu. Sternb erg Astronomical Institute, Moscow, Russia
In this brief note we want to show several new methods which allow to involve the data from existing huge stellar catalogues into the search and analyze of stellar clusters. We also show some preliminary but very promising results of those methods. Currently there are several compiled catalogues of stellar clusters, but they all have several significant disadvantages 1. There is a big percentage (tens of percents) of clusters in the catalogues which actually do not have any parameters measured, do not have a Color-Magnitude diagram (CMD), and are therefore just non-verified groups of stars. 2. A significant part even of well known big clusters do not have confident measurement of parameters (radius, distance, color excess). 3. All the clusters in catalogues came from very different sources, and nobody ever performed a really homogeneous search of clusters. But now the existing data in huge stellar catalogues really allow to overcome most of the problems mentioned above, and we can apply a really serious and uniform approach to the search and investigation of stellar clusters. Our work: 1. We have designed the method to search/find effectively stellar clusters of different radii in the star catalogues (like USNO, 2MASS etc.). This task is not so simple, and has not been performed by anybody before, because of highly variable mean stellar density. For this task we used a somehow modified method based on the convolution with density functions (fig. 4) 2. Also, we have designed a rather robust method which can be used to determine whether this density peak is just occasional overdensity of field stars or this is a real group of evolutionary related (lying on one isochrone) stars. In that method simultaneously we also find the position of the isochrone of the cluster. (This last steps are mainly based on the fact that in real clusters only stars lying on the isochrone show a density peak, but the field stars should demonstrate flat distribution (fig. 3). This fact allows to find the position of the isochrone of the cluster even when the CMD is "polluted" by field stars) So, briefly, we can find clusters, confirm them, and determine the main parameters (radius, distance and color excess) of those clusters. Our algorithms are mainly realized and programmed (we almost finished the automation of them). And surely we have performed some tests of them. The testing was based on several fields from 2MASS (2MASS is our primary target catalogue). And the results of the tests are quite promising. From the very preliminary analysis of the 250 sq. degrees in the Galaxy Anticenter region we have found several ( > 10) NEW clusters, and have determined the parameters for them (fig. 2). In that region also we were able to determine the parameters for several clusters without such measurements. Also, a set of new clusters was found when we just looked in the region of Perseus arm. (I should notice also, that the clusters, which we have found are not just infrared clusters, most of them are clearly visible in the optical wavelength range). Conclusion: As a result of our work we plan to obtain the new catalogue of confirmed stellar clusters, containing several percents of new clusters, and with homogeneously measured parameters. It would be interesting also to try to apply these methods to several other catalogues (DENIS, SDSS ...).


E-mail: math@sai.msu.ru

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Andrews-Lindsay 5 Havlen-Moffat21 Stephenson1 Arp-Madore7 Dutra-Bica993 AMKing67378 Ruprecht1020 Westerlund32 Terzan-Ju161 Collinder1876 Markarian875 Johansson38 vdBergh9954 Tombaugh12 Dutra-Bica61 ESO 4725125 Ruprecht113 Grasdalen6 2 NGC466535 Trumpler934 Loden26183 Berkeley242 Melotte4178 vdBergh595 Pfleiderer81 Bochum227 loden2451A Harvard134 Ruprecht12 Feinstein14 Mamajek11 Waterloo15 Trumpler12 Schuster13 Czernik1394 Loden1373 Antalova74 Dolidze225 NGC2451B Melotte202 Haffner213 Chupina34 Bochum26 Basel6735 Graham832 Platais991 Harvard631 Pismis23749 Carraro530 Loden11a Lynga894 Haffner23 Alessi 848 Muzzio8930 Shorlin111 Blanco105 Stock2313 Basel2326 Platais1424 Saurer101 Hogg2158 Turner1213 Pismis1114 Danks1516 Loden19 28 Moffat18 40 Mayer17 46 Lynga16 15 Auner15 31 IC 465129 Alessi23 11 BH102328 Basel915 Hogg807 Miller821 Sher 757 BH245610 0430-392 1353-265 BH6728 239118 239519 248820 258121 260222 271423 294424 294826 429127 245-09 485-20 252-14 486-45 486-54 424-25 425-06 489-01 425-15 426-26 309-03 427-32 367-10 559-02 559-13 429-02 429-05 493-03 429-13 368-11 258-01 368-14 311-14 123-26 494-09 561-05 311-21 430-09 430-14 430-18 312-03 312-04 370-13 313-03 370-17 432-03 313-11 313-12 260-06 211-01 260-07 211-03 371-25 260-17 165-09 166-04 261-03 211-09 314-14 261-07 315-14 435-09 435-17 092-05 435-33 435-48 436-02 092-18 062-08 168-04 062-11 437-61 128-16 265-01 502-19 570-12 093-08 129-19 129-32 217-08 130-06 130-08 130-13 064-05 131-09 442-04 065-03 324-15 065-07 383-10 445-74 097-15 021-06 175-06 447-29 134-12 008-06 329-02 099-06 275-01 389-05 226-06 137-23 277-04 518-03 137-43 332-08 332-11 332-13 043-13 587-04 332-20 278-02 332-22 392-13 334-02 139-13 393-12 393-15 520-20 456-05 456-09 456-29 229-02 589-26 139-54 521-38 456-72 522-05 335-05 522-16 281-24 524-01 397-01 282-26 231-30 141-47 337-23 525-08 461-38 026-02 464-09 236-07 10695 11096 11197 11898 12199 13110 13211 14012 14413 15014 15115 16416 17617 19725 20075 20233 20576 20836 21137 21477 21839 21779 221345 222451 223512 1252 1520 1557 1641 1785 1901 1891 1963 2017 2061 2132 2204 2215 2220 2225 2243 2250 2287 2302 2306 2309 2311 2318 2323 2348 2335 2338 2343 2345 2349 2352 2351 2354 2353 2358 2360 2362 2367 2364 2368 2374 2383 2384 2396 2401 2414 2413 2421 2422 2423 2425 2428 2430 2439 2432 2437 2447 2448 2453 2455 2477 2467 2479 2482 2483 2489 2516 2506 2509 2527 2533 2547 2539 2546 2548 2567 2571 2579 2580 2588 2587 2609 2627 2635 2645 2659 2660 2658 2670 2671 2669 2678 2682 2818 2849 2866 2910 2925 2932 2972 2982 2995 3033 3036 3105 3114 3228 3247 3255 3293 3324 3330 3446 3496 3532 3520 3572 3590 3603 3680 3766 3909 3960 4052 4103 4230 4337 4349 4439 4463 4609 4755 4815 4852 5043 5045 5138 5155 5168 5269 5281 5284 5288 5299 5316 5359 5381 5460 5593 5606 5617 5662 5715 5749 5764 5800 5822 5823 5925 5998 5999 6005 6025 6031 6067 6087 6124 6134 6152 6169 6167 6178 6192 6193 6200 6204 6216 6222 6208 6231 6242 6249 6250 6253 6259 6268 6281 6318 6322 6334 6360 6357 6374 6383 6396 6404 6400 6405 6415 6416 6421 6425 6437 6444 6451 6455 6469 6475 6476 6480 6494 6507 6514 6520 6531 6530 6529 6546 6554 6561 6568 6573 6583 6595 6596 6604 6605 6603 6611 6613 6588 6618 6625 6631 6639 6645 6647 6649 6664 6682 6683 6694 6698 6704 6705 6716 1929 2330 3431 3732 4733 52291 5466 5571 5672 5823 6010 6324 6611 6713 7214 7315 7525 7816 7917 8418 8519 8720 8821 9022 91192 92393 99494 1010 1095 1002 1101 1177 1171 1152 1202 1194 1225 1289 1282 1256 1378 1339 1375 1409 2115 2045 2159 172 143 112 165 153 213 189 306 309 280 336 372 402 466 467 481 480 565 615 624 682 694 10 58 11 33 12 37 13 36 14 44 2860 2718 4623 10 11 12 14 15 16 17 18 19 20 21 22 192 285 386 487 588 689 790 880 983 27 28 121 465 466 132 135 140 467 173 185 187 197 196 198 205 213 223 228 232 234 236 240 258 261 268 269 271 272 275 277 292 299 302 307 316 332 333 338 345 347 350 351 359 468 367 469 37 2 1 3 4 50 5 59 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 100 101 102 103 104 165 105 107 166 108 110 167 111 112 113 114 115 176 116 117 118 119 120 123 124 125 126 127 128 129 130 131 133 134 168 136 169 138 137 139 170 141 142 171 143 144 145 146 147 6 10 9 40 38 41 42 44 43 45 46 47 48 49 50 51 52 53 54 55 56 58 57 59 60 61 62 63 64 65 66 67 69 68 70 71 72 73 74 78 80 82 84 83 9 1 King 11 NGC 7762 Skiff 1 Berkeley 61 Berkeley 64 Berkeley 59

Pfleiderer 1 Stock 6 NGC 886 63 Stock 5 Berkeley NGC 609 NGC 637

Czernik Stock 18 45

Tombaugh 4

Stock 2 Basel 10

King 1 Berkeley 104 Berkeley 4 King Dolidze 13 16 Berkeley 62 Pfleiderer 4 NGC 133 NGC 146 King 14 Czernik 6 King 12 Berkeley 5 NGC 559 Stock 20 Harvard 21 Czernik 7 Frolov 1 Berkeley 7 Czernik 3 NGC 7788 NGC 7790 Stock 3 366 IC 166 NGC Stock King 15 Mayer 1 Czernik 1 24 NGC 654 Berkeley 58 NGC 225NGCNGC 103 King 13 136 Czernik 5 Berkeley 60 NGC 381 Czernik 4 NGC6663 Berkeley Trumpler 1 NGC 189 Berkeley NGC 7795 1 Dolidze 12 NGC 659 Berkeley 2 NGC 581 NGC 743 NGC 129 Czernik 2 NGC 433

NGC 436 NGC 457 Stock 4

King 2

Stock 21

IC 1590 NGC 744 NGC 657

Figure 1: The Region of Perseus arm (160 x 160 ). The top panel is the overdensity map obtained by our methods, the bottom panel is the same map but with overplot of known clusters. It can be seen that most of the known clusters correspond to the peaks on our map, so they can be easily detected by our method. But also, there are several peaks not corresponded to known clusters. These are new clusters. 2


Figure 2: Just two examples of NEW open clusters. Panels on the top ­ Color-Magnitude diagrams of clusters KSE5 and KSE18 with overplotted isochrones. Panels on the bottom ­ corresponding DSS images.

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Figure 3: The density plots for two clusters from previous plots (the red points are the density of points lying on the isochrone, the black ones are the density of stars lying "far" from isochrone on CMD). This plots allows us to determine the right isochrone position of the cluster, only when the isochrone is rightly positioned we will obtain the peak of red points (cluster), and the constant level of black points (field).

Figure 4: The illustration of the method based on density functions. Each ob ject from the catalogue is "transformed" to some predefined function and the summary image is computed.

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