Methanol maser and 3 mm line studies of EGOs

1. Methanol maser and 3 mm line studies of EGOs Xi Chen (ShAO) Collaborators: Simon Ellingsen (UTAS) Zhi-Qiang Shen (ShAO) Ye Xu (PMO) Jin-Hua He (YAO) 2009 East Asia VLBI Workshop, March 18-20 2009, Seoul

2. Outline • What is the EGOs • Methanol maser with EGOs • 3 mm line survey with PMO-13.7 m telescope • Future work • 95 GHz methanol and 3 mm line surveys with the Mopra-22 m • Mapping survey of 44 GHz methanol maser and SiO line with the EVLA • Studies of EGO with the KVN

3. What is the EGO: • Extended 4.5 um sources identified in the Spitzer GLIMPSE Galaxy survey, also called Extended Green Object (EGO; for the common coding of the [4.5] band as green in 3-color composite IRAC images.). • The extended emission in 4.5 um band is thought to be excited by shocks, such as those expected when protostellar outflows crash into the ambient ISM. • Cyganowski et al. (2008) have compiled a catalog of over 300 EGOs. Based on the association of EGOs with infrared dark clouds (IRDCs) and 6.7 GHz CH3OH masers, they further suggest that extended 4.5 um emission are indeed pinpoint outflows from MYSOs. • EGOs trace a population with ongoing outflow activity and active, rapidaccretion stage of massive protostellar evolution. Thus the EGOs provide the largest and newest working sample for massive star formation studies currently available.

4. Methanol maser with EGOs • 6.7 GHz Class II methanol maser in EGOs –Cyganowski et al. (2008) found that 73% of “likely” MYSO outflow candidate EGOs and 27% of “possible” outflow candidate EGOs are associated with 6.7 GHz class II methanol masers by comparing the EGO catalog with 6.7 GHz class II methanol maser catalogs of Elligsen (2006), Walsh et al. (1998) and Caswell (1996). –We re-compared the EGO catalog with the recent 6.7 GHz class II methanol maser catalogs (including Pestalozzi et al. 2005; Pandian et al. 2007; Ellingsen 2007), and found: • 105/147 EGOs are associated with class II maser sources within 1’ ; thus a high detection rate of 71% of class II maser in EGOs; • about 120 EGOs are not searched or no information for class II maser; thus 80 new 6.7 GHz class II masers are expected in these 120 EGOs. This has been searched with the telescopes of the University of Tasmania But only 44 new class II masers were detected due to the detection limit of ~3 Jy (3σrms).

5. Methanol maser with EGOs Sources Sensitivity Sample selection Survey Transition Searched Detected Jy Slysh et al. (1994) 44 GHz (70-61 A+) 250 59 5-10 HII regions, water and 6.7 GHz masers Val’tts et al. (2000) 95 GHz (80-71 A+) 153 85 ~ 6 HII regions, 6.7, 36 and 44 GHz masers Kurtz et al. (2004) 44 GHz (70-61 A+) 44 37 < 0.3 44 GHz masers, IR selected MYSO Ellingsen. (2000) 95 GHz (80-71 A+) 60 26 ~ 6 6.7 GHz methanol masers • Class I methanol masers in EGOs (Chen et al. 2009, MNRAS, submitted) –To investigate if there is any relationship between EGOs and class I methanol masers we have compared the results of four published class I maser searches with the EGOs: –We selected these four surveys for our statistical analysis because they include a large fraction (135/160) of the known class I maser sources.

6. Methanol maser with EGOs • Class I methanol masers in EGOs • This result shows the high association rate (~70%) between class I methanol maser and outflows for the first time on a statistical basis. • And the close relationship also suggests that outflows traced by both EGOs and millimeter molecular line observations provide reliable targeting criteria for searching for class I methanol masers.

7. 3 mm line survey with PMO-13.7 m telescope – The dynamics and process of massive star formation • Two opposing views regarding the massive star formation: • accretion similar to that of low-mass star formation, which accompanied by • outflow during the process of gravitational collapse; • coalescence of low-mass stars. –The large scale molecular infall is an important evidence for distinguishing two ways of massive star formation.

8. –The molecular infall can be identified from the blue profile of optical thick lines. Wu et al. (2007) Infall evidence: blue profile,optical thick line: two peaks with the blue one strongeroptical thin line: single peak at the line center

9. PMO-DLH 3 mm line survey with PMO-13.7 m telescope –HCO+ (optical thick line) survey: • 88 EGOs in the northern sky were observed; • on source time 15-25 mins for each source; • Detection rms: 50-80 mk; –C18O (optical thin line) survey: • 5-10 mins on source time • Detection rms: 60-100 mk

10. 3 mm line survey with PMO-13.7 m telescope –72 out of 88 EGOs were detected HCO+ emission • Detection rate 80% • The high detection rate suggests the presence of rich molecular gas in these sources –The HCO+ emission in EGOs is rather weak • most sources at 0.3-0.7 K (TA*)

11. 3 mm line survey with PMO-13.7 m telescope • From the HCO+ and C18O spectral profiles, we identified: Bule profile (27): double peak: 14 skewed profile: 13 Red profile (18): double peak: 7 skewed profile: 11

12. Some examples of blue profile HCO+ C18O

13. Some examples of red profile

14. 3 mm line survey with PMO-13.7 m telescope • Blue profile excess in the observed EGO sample (68 sources): (exclude 4 sources which show too complex spectral profiles) E=NB-NR/NT NB=27; NR=18; NT=68; E=13% The blue excess parameter is 13% in all EGO sample which is consistent with 15% found in Fuller et al. (2005) with a large sample (77). • Blue profile excess in different EGO samples: NB NR NT E 12 15 36 -8% IRDC 15 4 33 36% No IRDC 12 9 31 10% UC HII 12 8 29 14% CH3OH The molecular gas surrounding sources that are not IRDC (late stage sources) may be more adequately thermalized to show the blue excess

15. Future work • 95 GHz methanol and 3 mm line surveys with Mopra-22 m • Full EGO sample (~270 sources) The main observed line with 8 x 137.5 MHz bands: 1-0 HNC (90.6635680 GHz); 5k-4k CH3CN (five lines with ~ 92 GHz); 2-1 CS (97.9809533 GHz); 2-1 C34S (96.4129495 GHz); 80-71 A+ CH3OH maser (95.1694630 GHz); 2-1 CH3OH thermal lines (four lines with ~ 96.7 GHz) 1-0 N2H+ (3 lines with ~ 93.17) • A search for class I 95 GHz methanol masers in outflow environments associated with EGOs, and determine whether the detection rate of class I methanol masers are higher (70%) in outflow environment as is predicted by theory. • Search for evidence of outflow and infall in EGOs through observations of optically thick lines (CS and HNC) and estimate the cloud parameters (e.g. temperature and column density) through a series of CH3CN, CH3OH lines.

16. IRDC 18223-3 Beuther (2005) Future work • Simultaneously mapping survey of 44 GHz methanol maser and 7 mm SiO line with the EVLA • Investigate the detailed relationships between class I methanol masers and outflows traced by the thermal SiO line and the infrared IRAC images. Kurtz et al. (2004) H2O SiO H2 CH3OH Class I ?

17. Studies of methanol maser with EGOs and outflows with the KNV • EGOs and known outflow sources in the northern sky • ~ 90 EGOs; • 250 known outflow sources identified from mm line observations listed in Wu et al. (2004). • Mapping survey of 44 GHz methanol maser (higher resolution than VLA and ATCA). • Mapping survey of methanol maser at higher frequency transitions (e.g. 95 GHz if the KVN has this capacity ) . • Simultaneously mapping survey of methanol transitions at 7 & 3 mm, e.g. • 86.6, 86.9 GHz class II masers • 84.5 GHz class I masers • 44 GHz class I masers

18. Thank you