Help about science!

[Royston]

yeah right! whatever! thx to all this is my last post. Bye!

 

'There's no pleasing some people' Jesus

[Sayonara]

I predict many more Cs.

[insane_alien]

i've never seen someone get help quickly and then get mad about it and leave.

 

seriously, chillax. your going to have a stroke if you keep going like this.

[w=f[z]]

...And Indepedent research is hard I'm just looking for a crappy simple answer....

 

 

 

Since (I guess) this is the place for "crappy simple answers"...

 

Would any of you happen to be able to give me a crappy simple answer about the post-asymptotic giant branch star ZNG1 located in the globular cluster M5 (l=4,b=47.7, d=7.5 kpc). (This is my research project...)

 

Specifically, I'm working on a (future) publication in ApJ (I think... maybe MNRAS). Anyway, we observe material moving at high velocities (between -160 & -90 km/s relative to the local standard of rest (LSR)) that show absorption in OVI, CIV, SiIV for the high-ions and various low-ions. There seems to be various physical processes responsible for the ionization since the gas resides in multiple phases. Turbulent mixing layers (Slavin & Cox 1993) seeming to be the predominant culprit, but there is most likely some hodge-podge mixture of processes going on. Radiative cooling and collisional ionization equilibrium (CIE) (Gnat 1997) seem to be ruled out as we are unable to match the column densities where the column density ratios of the model match the observations. Conductive interfaces (Borkowski et al. 1990) seems to be ruled out due to the N(CIV)/N(NV) ratio and shock ionization (Dopita & Sutherland 1996) predictions doesn't match observations either [N(CIV)/N(OVI) ratio]. I still have to check the possibility of supernova remnants (Slavin & Cox 1992; Shelton 1998). I also still have to compare various properties with other observed HVCs to see if there is any systematic similar properties, etc.

 

Abundance measurements (from the OI/HI ratio) reveals that this gas is slightly super-solar in metallicity ([O/H]=+0.17 +/-0.09 +/- 0.05, where the last error is just a repitition of the uncertainties of the oxygen abundance of the sun). This super-solar abundance may, in part, be explained by the Galactic metallicity gradient (Smartt & Rolleston 1997; Rolleston et al. 2000). (Note that the ratio N(OI)/N(HI) is a good indicator of the metallicity since OI and HI have nearly identical ionization potentials and are strongly coupled through charge-exchange reactions (Field & Steigman 1971).)

 

Since ZNG1 is a pAGB star, this begs the question, "... is this material associated with the star, or is it a highly-ionized high velocity cloud (HVC) located in the Milky Way?" These high velocities get even higher relative to the photosphere (~-200 km/s) which seems quite high for a PN (typically 30-40 km/s).

 

Preliminary work with the photoionization code CLOUDY (Ferland et al. 2003; Ferland 2003) suggests that (in order to match the electron density (0.27-0.86 cm^-3)) this gas must be located at least 5 kpc away from the star, and that this gas must be several kpc thick - thus ruling out the planetary nebula (PN) hypothesis for the most part since it is too far away from the star and too thick to be a PN. It would seem that this gas is a HVC located in the Milky Way - perhaps associated with a nuclear Galactic wind. If so, this would be the first evidence that highly-ionized HVCs may be found near the Galactic disk.

 

So... the question is... what is this "stuff" I'm seeing and what is the origin of it?

 

I need a crappy simple answer! I don't want to get a "C." If I don't get quick answers I'll become very very mad.

 

Note: This is a tongue-in-cheek type of post....

 

Cheers,

w=f[z]

 

P.S. Manta - I'm just having fun... no hard feelings. Okay?