Documentation questions and definitions

[Espen Fredrick]

Hi all,

I'm an undergraduate student currently using this package for a senior project course. I am attempting to compare observed line ratios of M42 with those from a simulated spectrum using Cloudy. I've mostly just been following the examples and documentation to model the theoretical output spectrum, however I have some questions regarding things like units, which the documentation doesn't really give much insight on.

First things first- output types and units. When calling get_cont_y, your choices of output are ['incid' ,'trans', 'diffout' ,'ntrans', 'reflec']. While I can assume they refer to incident, transient, etc, what to they mean in regards to the output? How do these change the spectrum? Similarly, the units on output intensity are confusing. I understand "Jy" is Janskys, but what are the others?

In terms of abundances, these are in a different format than what I'm used to (12+log(O/H) I think...). Are these just log(O/H) in this case, no 12 added?

Finally, could someone help me understand r_min and dens? I see r_min is about 0.5ly in cm. Is dens the density of the modeled object, and if so in what units?

I'm sorry if my questions don't make any sense - I am still an undergraduate and learning as I go. This was based off an REU I did this summer so my knowledge on the topic is limited.

Thank you so much,

Espen

[Christophe Morisset]

Hi Espen,

On the units and meaning of the different columns of the continuum file (and what get_cont_y dives), I suggest you to read the Cloudy manual, Hazy1 section 16.44, you will find all the needed information. About the units, you can have the useful information directly from pyCloudy with :

help(pc.CloudyModel.get_cont_y):

which gives:

Help on function get_cont_y in module pyCloudy.c1d.cloudy_model:

get_cont_y(self, cont='incid', unit='es', dist_norm='at_earth')

    param:

        cont : one of ['incid','trans','diffout','ntrans','reflec', 'total']

        unit : one of ['esc' for erg/s/cm2, 

                       'ec3'for erg/s/cm2/C C : lightspeed,

                       'es' for erg/s,

                       'esA' for erg/s/AA,

                       'esHz' for erg/s/Hz,

                       'esAc' for erg/s/AA/cm2,

                       'ec3A' for erg/s/AA/cm2/C C : lighspeed

                       'esHzc' for erg/s/Hz/cm2,

                       'Jy' for Jansky,

                       'Q' for number of photons above the corresponding energy, 

                       'Wcmu' for Watt/micron/cm2, 

                       'WmHz' for Watt/Herz/m2, 

                       'WmA' for Watt/Anstrom/m2, 

                       'phs' for photons/s, 

                       'phsmu' for photons/s/micron, 

                       'phsc' for photons/s/cm2, 

                       'phsmuc' for photons/s/micron/cm2]

        dist_norm : one of ['at_earth', 'r_out', a float for a distance in cm]

    return:

        continuum flux or intensity

The abundances are in log(X/H). The radius are in cm, and densities in e/cm3, both using the log value. 

pyCloudy is mainly an interface to Cloudy : I thus strongly suggest you to have a look at the Quick Start document and the Hazy Cloudy manual, it may help you to understand the meaning of the different keywords and the units of the parameters.

Hope it helps,

Christophe