1. Millimeter Megamasers and AGN Feedback
Junzhi Wang
SHAO
Collaborators：Jiangshui Zhang(GZU), Yu Gao(PMO), ZhiyuZhang(ESO,PMO),
Di Li(NAOC), Min Fang(PMO), Yong Shi(NJU)

2. Outline Maser and Mega-maser Our research: 2 new mega-maser molecules
Future prospects: high resolution observations with JVLA and ALMA?

3. Astronomical Maser
Mainly in star forming regions, evolved stars and also Supernova remnants
More than 10 molecules were found to have maser emissions (OH, H2O, CH3OH, H2CO, SiO, HCN, CH, NH3,etc.)
Masers can be pumped by collision or radiation
Masers can be used for astrophysical and astrometry studies, such as BeSSeL project

4. Mega-masers Masers in galaxies had been found since 1970s
Some of them are similar to that in the Milky Way sources, and are just the collection of such maser emissions
Another type, the so-called mega-masers, with the isotropic luminosity greater than 1 million times than typical Galactic masers, and are not the simple collection of millions of maser spots similar to that in the Milky Way sources
Such mega-masers are normally formed in extreme conditions different to that in the Milky Way

5. History of Mega-masers
First mega-maser：Water in NGC4945, 1975, nature
OH in Arp220, 1982, ApJL, and H2CO in Arp220, 1986, ApJ
Many searching projects of new mega-masers had been done in past 30 years, mainly focus on class II CH3OH mega-masers, without success
Water mega-masers had been used to study the central super massive black holes and to determine the Hubble constant with the measurement of distances
OH mega-masers had been used to study the starburst in the central 100pc
Few works on H2CO mega-maser
For more information, see Lo (2005) ARA&A

6. What we have done
3mm observation toward the nearby type 2 Seyfert galaxy NGC 1068 with the IRAM 30m telescope
27 hours observing time, Dec 2011, PI: Junzhi Wang
We detected SiO and CH3OH mega-maser emissions, which increased the mega-maser molecules from 3 to 5

7. NGC 1068
This composite image shows X-ray (red), optical (green), and radio (blue) data credit: NASA/NRAO/NSF

8. SiO thermal emission in NGC 1068
Qiu et al. to be submitted
Usero et al. 2004

9. IRAM 30m

10. Dust continuum in NGC1068 The dash circle is the beam of IRAM 30m
at 3mm
349GHz dust continuum emission observed with ALMA, provided by Santiago Garcia-Burillo

11. Observations Date: Dec 2011, 3 days Observing mode: Wobboler switching
Backend: FTS
Receiver: EMIR
Observing band: 3mm (84-92 GHz)

12. Our results
Junzhi Wang, Jiangshui Zhang, Yu Gao, Zhi-Yu Zhang, Di Li, Min Fang, Yong Shi
Nature Communications，2014

13. They are real emission
We checked them at 2 LO tunings and detected them at both setups
The entire spectrum at 3mm was at extreme good performance, flat and stable baseline
SiO J=2-1 (v=1) can also be seen at similar velocity to that of v=3

14. Spectra of two LO tunings of SiO J=2-1 (v=3) for the 1125 km s-1 component

15. 8 GHz frequency coverage spectrum at 3mm

18. They are masers
The only on SiO J=2-1 (v=3) emission detected in the Milky Way is maser emission instead of thermal emission
And the line widths of SiO J=2-1 (v=3) in NGC 1068 are much less than the thermal lines, so it is reasonable to assign them as masers
CH3OH E line can be maser or thermal emission in the Milky Way sources
The detected CH3OH emission is more than 3 times of that estimated from other millimeter CH3OH lines detected with ALMA as thermal emission
And the line profile is different to the thermal lines

19. They are mega-masers
They are more luminous than one million times of the typical Milky Way masers
It is impossible to have more than one million evolved stars with maser emissions near the center of this galaxy (for SiO)
And the velocity of CH3OH emission is consistent with the jet maser of H2O, while the velocities of SiO masers are similar to the H2O disk maser

20. Possible origin of these two types of mega-masers comparing with H2O maser
22GHz continuum
Spectrum of H2O maser
Gallimore et al ApJ

21. Excitation conditions
The upper level energy of SiO v=3 is about 3660K
SiO molecules are needed: Shock or XDR?
Pumping mechanism: collision or radiation?
CH3OH: class I maser, collisional excitation

22. Future prospects Measuring the masses of central
AGN feedback: from sub-pc (SiO) to ~100 pc (CH3OH) scale
Other applications
High resolution high sensitivity observations, especially with ALMA
Single dish surveys: CH3OH mega-masers (Millimeter and MHz with FAST?)
Millimeter VLBI including ALMA?

23. Searching such emission in other galaxies
NGC 4258 and NGC 3079
IRAM 30m, Dec 2012
Observing time: about 10 hours each source
Not detected

24. Thanks