Revista Mexicana de Astronomía y Astrofísica ISSN: 0185-1101 [email protected] Instituto de Astronomía México

González-Fernández, C.; Negueruela, I.; Marco, A.; Clark, J. S. AN ACCURATE DISTANCE SCALE TO THE EXTREMELY MASSIVE CLUSTER Revista Mexicana de Astronomía y Astrofísica, vol. 42, 2013, pp. 8-9 Instituto de Astronomía Distrito Federal, México

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Rodríguez-Espinosa 8 a aeu o10 to up have al. may et and (Negueruela 2012) 10, Gonz´alez-Fern´andez Alicante Negueruela 2011; and & 7 Alicante RS- other GCs, contains which association, extended an by ∼ 4 have saothl h ieo tpesn2( 2 Stephenson of size the half about is lsesi tpesn2(SC) aise al. et 7 Davies within RSGs (RSGC2). 25 found 2 (2007) Stephenson these uncertainties. is of massive large though most clusters the to 2009b), models, these al. subject to According et are (Clark estimates RSGs these against of calibrated number models the synthesis us- population estimated be ing heavy can through populations seen Their They been obscuration. have Arm. be- these (RSGCs), only Clusters the cause Supergiant of Red as base known the are at found been eMxA(ei eConferencias) de (Serie RevMexAA el enl nvria eAiat,Ad.9,E38 Ali- E03080 99, ([email protected]). Apdo. Spain Alicante, cante, de Se˜nal, Universidad la de range, Myr mass 14–20 a the suggest in models age synthesis estimated population an For tre. iia gs xetRG1( RSGC1 have All except ages, far. so similar found been have clusters RSGC other est,Wlo al itnKye,M76A UK. 6AA, MK7 Keynes, Milton Hall, Walton versity, lse tpesn2suyn o h rttm t ansqec stars. presen sequence dis We main age, its clusters. as time the (such first Words: to parameters the Key distances fundamental for accurate derive studying I to determine 2 found. Stephenson program to been cluster ongoing need have supergiants an we red of region, of region vast clusters results this five a of least of at nature existence where the the Arm, revealed Scutum have the of two base last the during Discoveries utili 2 Stephenson estudi c´umulo principal. masivo c´umulos un de secuencia del cinco de su menos resultados de al etc.) estimaciones estrellas primeros encontrado regi´on necesitamos distancia, los han esta presentamos (edad, se de trabajo par´ametros que fundamentales naturaleza este la la En en c´umulos. entender Escudo-Cruz, estos gran Para de una brazo rojas. de del gantes existencia base la la establecido en ´ultimos a˜nos han estelar los en descubrimientos Sucesivos × 62 y;Cake l 09) u ssurrounded is but 2009a), al. et Clark Myr; 16–20 1 2 eea lseso e uegat RG)have (RSGs) supergiants red of clusters Several eatmnod ´sc,Igne´ad itmsyTeor´ıa y Sistemas F´ısica, Ingenier´ıa de de Departamento eateto hsc n srnm,TeOe Uni- Open The Astronomy, and Physics of Department 10 NACRT ITNESAET H XRML MASSIVE EXTREMELY THE TO SCALE DISTANCE ACCURATE AN M 4 cl M ≥ ⊙ aay pncutr n soitos niiul—Glx:selrcon stellar : — individual associations: and clusters open Galaxy: 3 n ehp pt 8 to up perhaps and × 10 .INTRODUCTION 1. 4 5 M .Gonz´alez-Fern´andez,C. M ⊙ ⊙ Dve ta.20) RSGC3 2008). al. et (Davies nttl h nlRSGC, final The total. in ∼ 2Mr,wihmay which Myr), 12 ′ ftecutrcen- cluster the of × LSE TPESN2 STEPHENSON CLUSTER , 10 42 4 – (2013) 8–9 , ∼ M 5RSGs, 15 ⊙ 1 Four . M .Negueruela, I. cl ABSTRACT RESUMEN ≥ erI weetecutr aebe ofrstud- far so been have clusters the the in (where RSGs IR for near diagnostics luminosity absolute no 50 2010a). al. et Negueruela mr hna re fmgiue sprogenitor as magnitude, 10–40 from of range order may masses an type in- spectral than given significant are a (more very at clusters luminosities a of the show spread trinsic RSGs to distances estimates. rough the because options (Negueruela ends Bar 2010a). at Long al. located the et ring, formation where distance huge our the along a projection of a sight or of 2008) line al. Bar et Long Davies Galactic 1999; al. (L´opez-Corredoira the et Arm of Scutum tip the starburst with the interacts localised where a point is considered: the at Complex been have Scutum in ideas the clusters main either massive Why Two of Group. region? concentration this Local a such the there in the in is likely region most formation and star Galaxy, far be by higher- to massive out the most turn acquired the by will association recently confirmed this have AAT/AAΩ, is with we this similar If spectroscopy velocities radial resolution cluster. observed with the RSGs have be to We to likely are stars. red ∼ luminous are they lcne8 ssalr( smaller is 8, Alicante 1 0 addtswt YFSadmr hn20 than more and WYFFOS with candidates 100 ′ ehv dnie eea ude bet within objects hundred several identified have We tpeet ecno eiebtenteetwo these between decide cannot we present, At .Marco, A. fSehno hs nrrdclussuggest colours infrared whose 2 Stephenson of 1 n .S Clark S. J. and et—supergiants — tent ∼ fsa omto ls othe to close formation star of etnd salcrlos establecer a destinado o 62 Myr, 16–20 ac,ec)t h massive the to etc.) tance, rcssd adsacaa distancia la de precisas re ounderstand to order n 2 M eio eformaci´onregi´on de ad aael las ello para zando ⊙ .Sneteeare there Since ). M eetefirst the here t cl ≥ 10 supergi- 4 M ⊙ ; © 2013: Instituto de Astronomía, UNAM - Fourth Science Meeting with the GTC Ed. C. Muñoz-Tuñón & J. M. Rodríguez-Espinosa band o agtwith target a For obtained. 16 f06ace eouinof resolution a arcsec 0.6 of other of mass. estimation total our the as refining such the cluster, parameters constrain the the to identifying help of would Also, age sequence main the 2. of sample can Stephenson tip significant distance for a spectroscopic derived a with be stars RSGs, sequence the main than of of of constrained case function better the luminosity much in the is sequence as main and the 2010b), al. et (Negueru- ela classification spectral accurate perform to OSIRIS. and GTC using obtained be can quality Sshave RSGs e fSehno .A h bcrto rudthis around cen- obscuration the the is As around cluster 2. criteria Stephenson a these of select fulfilling ter can stars we of UKIDSS set and 2MASS from tometry xetdt earound be to expected tu eetos,alwn o h ml ffe that effects, fringing offset remove to small needed scheme, the ABBA for the serendip- allowing of detections), number itous indeterminate two an includes pointing (plus every that objects way a such in lected S/N=100. obtain to s 2000 of exposure an h pseudo-colour the a oeta a nuenncruaiyi h or- uncertainty. the the the in increasing substantially non-circularity of bits, induce presence may the this potential that And Bar account into parameters. taking cluster before other to through feed etpito h aatcamrslsi eysig- very distances in dynamical results their (5 arm in galactic uncertainties tan- the the nificant uti- to of be close point clusters to these gent had of have position The curve rotation lized. Galactic derived a distances been seen, from kinematic not been Consequently have have RSGC1-5 derived. members to distances unevolved spectroscopic no and ied), nyifae htmty al yesasaeex- are roughly stars have type to Early pected using photometry. populations infrared separate only to effectively used be can . 8 .SLCIGTEMI EUNEOF SEQUENCE MAIN THE SELECTING 2. m < sn SRSwt t 20Igimadaslit a and grism R2500I its with OSIRIS Using used be can band this in spectra resolution Low stetre est shg,si nlsaese- are angles slit high, is density target the As shsbe hw yNgeul ta.(2011), al. et Negueruela by shown been has As − +1 0 . . 9 8 i p o tpesn2,wihconsequently which 2), Stephenson for kpc < A K m 17 K 1 = . .Therefore, 5. .OBSERVATIONS 3. ∼ . 4 nthe in 44, ,tetpo h ansqec is sequence main the of tip the 5, TPESN2 STEPHENSON Q ( = m − J K 0 . − 16 ∼ ∼ i NACRT ITNET TPESN29 2 STEPHENSON TO DISTANCE ACCURATE AN m I 50aon 8500 around 2500 H adteesashave stars these band i adsetao high of spectra band ≤ 1 obnn pho- Combining 11. ) 17 = − Q 1 ≤ . . hsrequires this 0 8 0 × . 8 sthe As 08. ( H − is A ˚ K S ) eurea . lr,J . ici,B .2010b, & W. A., B. Gonz´alez-Fern´andez, Marco, Ritchie, I., C., & Negueruela, S., J. Clark, I., Negueruela, A., Marco, Gonz´alez-Fern´andez, C., I., Negueruela, al. et E., J. Beckman, Garz´on, ApJ, L´opez-Corredoira, F., M., 2008, al. et 539, J., A&A, C. 2012, Gonz´alez-Fern´andez, I. Law, Negueruela, F., 2007, C., D. al. Figer, et B., R.-P., Davies, Kudritzki, F., D. A&A, Figer, 2009b, B., al. Davies, et F., Najarro, B., Davies, S., J. Clark, A&A, 2009a, al. et B., Davies, I., Negueruela, S., J. Clark, eurs noengto bevto,sxobserving six obtained. observation, where of (OB) night blocks one In requires. nfr,wt mean a with uniform, values, older Myr. towards 20 estimation around age the tips cluster previ- than away farther suggests thought. slightly it ously is merit, cluster of figure the reliable that a obtain to us low a performed: parameters, already precise be derive can estimation to first enough ample not esti- its significantly mass. change initial could mated around that cements RSGs of supergiants cluster population be the diffuse ran- to a 23 of out of existence sample turn the a 1/4 from that stars, Davies fact dom The to according (2007). al. 2 popula- et Stephenson the in supergiants, dominant M tion early being with patible appear stars population. other sequence, blue compatible Three foreground blue B5. be be cluster to to to B1 the from out of types turned with members 8 being targets, with 11 detections. the background/foreground Of 23 and targets .FRTRSLSFO H PROGRAM THE FROM RESULTS FIRST 4. lr,J .21,AA 2,A59 528, A&A, 2011, S. J. Clark, A78 516, A&A, Mart´ınez-N´u˜nez,A74 513, & A&A, S., 2010a, J. S. Clark, 381 118, AJ, 1999, A100 1016 676, 781 671, ApJ, 429 504, 109 498, h xicinoe h edsest erather be to seems field the over extinction The the - of sequence blue the of composition The - al- not does sample limited very our Although - is stars sequence main of sample our Although com- spectra have 5 objects, serendipitous 23 Of 11 recovered: where spectra 34 OBs, these From REFERENCES E ( J − K S 1 = ) . 68 ± 0 . 13.