PoS(IX EVN Symposium)058 http://pos.sissa.it/ ce. anol masers in star forming liminary results for five of them. the Golden Age for Radio Astronomy is a very valuable astrometric tool, gions have been observed during five akes it ideal to measure proper motions stronomy and Astrophysics at the Universities of as, which still have the potential to be improved by more µ ive Commons Attribution-NonCommercial-ShareAlike Licen † ∗ [email protected] [email protected] [email protected] [email protected] [email protected] Speaker. Member of the International Max Planck Research School for A ideal observational circumstances. regions of the Galaxy. The 6.7 GHzfor methanol its maser large transition stability and confined velocity spread,and which m parallaxes. Eight well-studied massiveEVN star sessions forming of re 24 hours duration eachWe and achieve we accuracies present of here up pre to 51 We present the first EVN parallax measurements of 6.7 GHz meth ∗ † Copyright owned by the author(s) under the terms of the Creat c Bonn and Cologne. The 9th European VLBI Network Symposiumand on EVN The Users role Meeting of VLBISeptember in 23-26, 2008 Bologna, Italy Kazi L. J. Rygl Distances to Galactic methanol masers Andreas Brunthaler Max-Planck-Institut für Radioastronomie, Germany E-mail: Karl M. Menten Max-Planck-Institut für Radioastronomie, Germany E-mail: Mark J. Reid Harvard-Smithsonian Center for Astrophysics, USA E-mail: Huib Jan van Langevelde Joint Institute for VLBI in Europe,Sterrewacht the Leiden, Netherlands Leiden University, the Netherlands E-mail: Max-Planck-Institut für Radioastronomie, Germany E-mail: PoS(IX EVN Symposium)058 eriment Kazi L. J. Rygl to 10 kpc (see for , but frequently much 1 rk that had receivers for − from warm dust, heated by a rometry satellite GAIA, to be asses, 20% fainter luminosities GHz inhabit both these regions, 20 kms s of the order of a kilojansky, but fficult. The only method which thanol masers results in different ity to measure. First, the determi- ne also needs distances on a large ong and compact sources. Masers ∼ FRs with strong methanol masers. iated with high mass SFRs. Water ards the Orion Nebula, determined ortant complement to GAIA; radio e stability needed for optical wave- cally thick part of the quasar, while nt on Hipparcos! re the ionosphere is typically more hich is manifested by a large velocity e referencing techniques can provide allax, which is simply a geometrical quires for phase referencing depends art and hence one can encounter more pportunity to start a project measuring ation regions (SFRs) and AGB stars, ze-scale, the mass, the luminosity and rned out to be 10% smaller than previ- as, and therefore provide important re- tant impact on the study of massive star cy reachable in the optical, GAIA will had an accuracy of 0.8-2 mas, allowing r frequencies the signal is more affected vations. Historically, the first dedicated anol masers are preferred for astrometry. µ nd dense dust lanes in the Galactic plane. 2 200 pc (with error bars of 20%). However, this successful exp ∼ as for obtaining accurate (with error bars of 10%) distances µ When the project began in 2006, the EVN was the only VLBI netwo To measure the trigonometric parallax one requires very str Unfortunately, accurate distance measurements are very di In astronomy, accurate distances are a very important quant smaller [11]. The frequencysources of difference disturbance between for each water ofby and the transitions. me tropospheric At delay highe errorsdominant. than Also, at the lower positional frequencies, accuracyon of frequency. whe the At quasar high one frequencies re at one lower observes frequencies the one more is dominated opti extended by structure. the optically thin p observing the 6.7 GHz maser transition.the It offered parallaxes a and unique o proper motionsAccurate towards distances eight towards these well targets known will have S an impor spread. Methanol masersyoung are stellar thought object to be and pumped have velocity by emission spreads of maximally Water masers are often associated with outflows in SFRs [2], w example [3],[12] and [9]). This is up to a 100-fold improveme are the ideal targets,objects found whose frequently distances in one wants (dusty)while to star methanol know. masers form Water (12 masers andand at 6.7 6.7 22 GHz) GHz are methanol exclusively masers assoc canbecause be of very their strong, stability with and confined peak velocity fluxe spread meth It is in these regions that radio astronomy can provide an imp sults on Galactic-scale distances.suffer Despite from the dust extinction, high especially accura towards the large a wavelengths do not suffer from dust extinctionaccuracies and up VLBI to phas 10 nation of many physical properties ofthe objects, age such depend as on the the si by distance. a For trigonometric example, parallax of theously radio distance continuum tow assumed. stars [6], The tu implicationsand of 20-30% this younger are ages a for 10%scale the to drop stars study in in the the the structure field. m of our Moreover, o Galaxy. allows an unbiased measure ofmethod, distance and is therefore trigonometric free par oflengths, any parallax assumptions. measurements require To achieve space-borne th optical obser satellite for this purpose wasit Hipparcos to [7], measure which distances to Distances to Galactic methanol masers 1. Introduction could reach only alaunched tiny in part 2012, of will the be Milky able Way. to attain A accuracies new of optical 20 ast PoS(IX EVN Symposium)058 f 512 Mbps. geodetic-like Kazi L. J. Rygl at 6.7 GHz. The 1.2 hours on each 1 ∼ − % correlated, and is lays were estimated for from the ammonia spectral 0.9 and cessing System (AIPS). The etween 2006, June and 2008, ∼ served in a cycle with one (or fit, the error was multiplied by erved strong masers we could se of the outflow. In 2006, Imai rly indicate a bipolar outflow. An rs and made use of ited by time smearing). The maser 10 minutes, also every 6 hours, and the sky position; half of our targets he data were reduced following the ere fitted, yielding the parallax and of 8 MHz bandwidth with a channel adial velocities of water masers [4]. ferred in a created 8IF dataset to the ∼ dard gain curves. The correction for rope (JIVE), using an integration time ed by fitting 2D gaussians to the maps. between odrell Bank, Westerbork in single dish ion, with a bandwidth of 8 MHz and a lution of 0.35 kms c delay corrections. Amplitudes were sthoek, Cambridge (first 3 epochs) and al observing run contained 4 geodetic 3 06 mas (shown in Figure 1), corresponding to a distance of . 0 ± 12 . ) quasars. The observations were performed with a data rate o ◦ 2 − ◦ 1 is the number of spots. This allows the random errors to be 100 observations were reduced separately, and tropospheric de ∼ N 1 hour every 6 hours, 4 blocks of fringe finders of ∼ 48 pc – very close to the kinematic distance of 850 pc obtained L1287 is an interesting SFR, where CO observations [13] clea The observations were performed at five epochs using the EVN b The data reduction was done using the Astronomical Image Pro Using the technique of phase-referencing, each maser was ob (1,1) study [1] shows that there is cold and dense gas at the ba ± , where 3 N therefore a conservative and safe approach. 3. Preliminary results 3.1 L1287 NH geodetic-like observations to calibrate the tropospheric delays. A typic March. The antennas participating in thismode, experiment Effelsberg, were Medicina, J Torun, Onsala, Noto, Hartebee one VLA antenna (last epoch). Each observation lastedblocks 24 of hou Distances to Galactic methanol masers formation in these regions. 2. Observations and data reduction 891 quasar sources were correlated in continuumseparation mode with of 8 0.25 IFs, MHz. lines. 4 blocks of maser/quasar observations, spending on average maser. The difference in observing timeare per low maser declination depends sources, on and have a limited visibility. two) nearby ( The data were correlated at the Jointof Institute 0.5 for seconds VLBI affording in a Eu fielddata of were view correlated of using 1.2 one arc IFchannel minutes with separation high (lim of spectral 7.81 resolut kHz, resulting in a spectral reso each antenna (see [8]) and correctedEVN with guidelines, the applying task ’CLCOR’. parallactic T anglecalibrated and using ionospheri system temperature measurementsthe and Earth stan rotation wasuse done them with as the the phase taskcontinuum reference, data. ’CVEL’. and The Since the quasar and solutions we maser were obs positionsThe trans were differences extract in position between aproper maser motions. and√ When quasar more pair than w one maser spot was used for the et al. found evidence forWe a measure disk a from parallax the of distribution 1 of the r PoS(IX EVN Symposium)058 ). ◦ > 25 δ Kazi L. J. Rygl ained due to a as, corresponding to a µ 24 kpc [3]. We were not . 0 , we briefly discuss the re- cension (solid line) and declina- ± parallax of 6.7 GHz methanol tions obtained from the water water masers to this SFR in the ined [9]. The last three sources 28 nts). Nevertheless, we can study and we do not discuss them here. . of higher declinations ( t was large; it consisted of eight the quasar in some epochs. How- acy of 51 GHz maser transition with the EVN Honma et al. with our observations gnature (peak, valley). For NGC281- 1287 with ON1 in Figure 1), for which essions, we did not manage to have the as, which is 10 – 20 times better than d water maser distribution in this SFR. µ maser channel which was used for the parallax 4 78 kpc, which is in excellent agreement with the . 50 – 100 0 ∼ ± 53 . as corresponding to a distance of 5 µ 8 ± 17 kpc (shown in Figure 1). This is the highest accuracy we obt . 0 ± 75 . The preliminary results for L1287, S269 and ON1. The Right As We have demonstrated that one can measure the trigonometric A summary of the preliminary results is given in Table 1. Here In 2007, Honma et al. measured the trigonometric parallax of masers using the EVN. Good results were obtained for sources water maser results [10]. Forever, S252 S252 we had did not a manage recent(not to 12 in detect the GHz Table), methanol S255, L1206 maser and parallax MonR2, determ are being worked on 4. Discussion favorable sky position and a goodW sampling we of the obtained parallax the si largest distance of 2 maining results. We measure the parallax of ON1 with an accur 3.3 Overview able to reach the necessary(Figure 1 accuracy shows to the verify parallax the ofthe Honma results methanol et of proper al. motions andmaser our and to measureme compare test intrinsic them differences to between the the methanol proper an mo distance of 1 Hipparcos. The accuracy of parallax measurementscan of be the improved 6.7 by takingmasers, all notice at of different the R.A.s and following.ideal declinations. parallax signature In Our coverage the for projec five each maser s (compare L Figure 1: Distances to Galactic methanol masers The accuracy reached in this experiment is tion (dashed line) signature offitting the is parallax indicated are by shown. a Each different color. 3.2 S269 outer Galaxy to be 189 PoS(IX EVN Symposium)058 7 mas . 3 × 7 . Kazi L. J. Rygl ; [5] ; [1] kin kin Literature D irst, the errors introduced by ved with the EVN, are a well l masers. The final astrometry ecently equipped with 5 GHz re- t manage to observe them as long sions were near the zero-signature of the beam is more elongated in kinetic ics in the light of the new distance efore, determining the S/N with or e S269 has a beam of 7 es the corrections did not improve the lative to Galactic motion. , 889 oblem encountered in the project was s in declination are significantly worse phere, is not possible with most of the ys a more important role, and actually observations. We find an improvement rmined delay as of tropospheric origin. h their low elevations, resulted in a poor 16, 1897 , ApJ 645, 337 in: Proceedings of 8th EVN Symposium error D 1993, ApJ 419, 698 049 0.850 D . 78 2.7 2.8; [10], parallax 17 1.8 D . . 0 ± 0 0 correction. A dual frequency observation mode, ± 5 ± ± geodetic-like 53 75 891 parallax . . . geodetic-like error D 1 2 051 1 059 0 . . . ± 0 0 0 ± ± ± RELIMINARY DISTANCES AND LITERATURE VALUES P . ◦ 395 572 123 . . . mas kpc kpc kpc correction in each observation is the best option for now. Table 1: geodetic-like S269S252 - - - - 3.0 4.4 5.3; [3], parallax 2.1; [9], parallax NGC281-W 0 ON1 0 SFRL1287 Parallax 1 Finally, we would like to touch upon the As in previous parallax studies, the position uncertaintie In conclusion, we have shown that 6.7 methanol masers, obser coverage. v , [4] Imai, H., van Langevelde, H. J. & Umemoto, T., 2006 [2] Hachisuka, K., Brunthaler, A., Menten, K.[3] M. et al., Honma, 2006 M., Bushimata, T., Choi, Y. K. et al., 2007, PASJ 59 [5] MacLeod, G. C, Scalise, E. Jr., Saedt, S. et al., 1998, AJ 1 [1] Estalella, R., Mauersberger, R., Torrelles J. M. et al., with a position angle of 55 in the calibration for most of thecalibration. cases. We However, in suspect a that few here cas we the degrade ionospheric the calibration delay by pla wronglyIn interpreting these the cases, dete we did not apply the as employed in geodetic observationsEVN to calibrate antennas. the ionos Also switchingwithout receivers a is impossible. Ther u of the parallax, decreasing thethe quality large of number the (50%) fit. ofas Another low-declination their pr sources. high declination We counterparts. did This, no combined wit than in Right Ascensionthe (see atmosphere for are example larger L1287declination in than in declination. in Figure Right 1). Ascension. Second, the For F example, shape the sourc one prefers to sample the peaks. Often, as for L1287, some ses Distances to Galactic methanol masers suited tool for astrometry.ceivers The is fact a that sign theof VERA for our array a sources was growing will r enthusiasm bedeterminations, for and used 6.7 to to study GHz reevaluate the methano the 3D SFRs’ velocities of astrophys the SFRs re References PoS(IX EVN Symposium)058 , 81 Kazi L. J. Rygl nce 311, 54 J in press, arXiv:0811.0595 in: Proceedings IAU Symposium 242 , 2007, A&A 474, 515 7 1995, A&A 304, 69 6 [6] Menten, K. M., Reid., M. J., Forbrich, J. & Brunthaler, A. [7] Perryman, M. A. C., Lindegren, L.,[8] Kovalevsky, J. et Reid, al., M. J. & Brunthaler, A.,[9] 2004, ApJ Reid, 616, M. 872 J., Menten, K. M., Brunthaler, A. et al., 2008, Ap [10] Sato, M., Hirota, T., Honma, M.[11] et al., Sobolev, 2008, A. PASJ M., 60, Cragg, 975 D. M., Ellingsen, S. P et al., 2007 [12] Xu, Y., Reid, M. J., Zheng, X.[13] W. & Yang, Menten, J., K. Umemoto, M. T., Iwata, 2006, T. 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