AbsSystem Class¶

Notebooks¶

Simple Examples

Overview¶

This Class is designed to organize and analyze an absorption system. This is generally constructed of one or more AbsComponent Class. The base class is abstract, i.e. one must instantiate one of its flavors (e.g. HILyman, MgII, LLS, DLA).

By definition, an AbsSystem is a unique collection of absorption components. It is specified by:

Property	Variable	Type	Description
RA, DEC	radec	tuple or coord	RA,DEC in deg or astropy.coordinate
Redshift	z	float	absorption redshift
Velocity limits	vlim	Quantity array	-/+ velocity limits of the system

Instantiation¶

The AbsSystem Class may be instantiated in a few ways. The default sets the properties listed above:

gensys = GenericAbsSystem((15.23*u.deg,-23.22*u.deg), 1.244, [-500,500]*u.km/u.s, NHI=16.)

More commonly, one will instantiate with one or more AbsComponent objects:

# HI Lya, Lyb
radec = SkyCoord(ra=123.1143*u.deg, dec=-12.4321*u.deg)
lya = AbsLine(1215.670*u.AA, z=2.92939)
lya.limits.set([-300.,300.]*u.km/u.s)  # vlim
lyb = AbsLine(1025.7222*u.AA, z=lya.attrib['z'])
lyb.limits.set([-300.,300.]*u.km/u.s)  # vlim
abscomp = AbsComponent.from_abslines([lya,lyb])
abscomp.coord = radec
# Finish
HIsys = LymanAbsSystem.from_components([abscomp])

One may also instantiate from a dict, usually read from the hard-drive:

abscomp = AbsSystem.from_dict(idict)

Attributes¶

Sub Classes¶

Generic¶

A catch-all subclass for AbsSystem. More options are provided in pyigm.

Plots¶

Methods¶

AbsLines¶

There are a few methods related to the AbsLine objects within an AbsSystem.

List¶

One can generate a list of all the AbsLine objects with:

lines = abssys.list_of_abslines()

get absline¶

One can retrieve one or more AbsLine objects matching the name or rest-wavelength of a transition, e.g.

lyb = abssys.get_absline('HI 1025')
# or
lyb = abssys.get_absline(1025.72*u.AA)  # Nearest 0.01 A is required

measure_restew¶

Measure the rest-frame equivalent widths for all AbsLine objects in the system. In addition to the inputs described in measure_ew, each line to be measured must have line.analy[‘do_anlaysis’]=1. Here is an example:

abssys.measure_restew(spec=xspec_object)

fill transitions¶

Generate an astropy.Table of information on the absorption lines in the system. This is stored in the ._trans attribute:

abssys.fill_trans()
print(abssys._trans)

Components¶

~linetools.igsm.abssystem.get_component grabs components matching an input where the input is either a tuple of (Z, ion) or an AbsLine:

SiII = gensys.get_component((14,2))

~linetools.igsm.abssystem.update_component_colm synthesizes and updates the column densities for the components.:

gensys.update_component_colm()

ionN¶

Fill the _ionN attribute with a QTable of column densities. These are derived from the components

abssys.fill_ionN()
print(abssys._ionN)

Output¶

One may generate a dict of the key properties of the AbsSystem with the to_dict() method:

odict = HIsys.to_dict()

This dict is required to be JSON compatible.

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