Add Milky-Way extinction

One usually wants to draw targets while including the Milky Way dust extinction effect. Such effect can be accounted in Target for using the effect= option in from_draw() or using add_effect().

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How it works

skysurvey.Effect enables to change a target and the way we simulate spectra and lightcurves.

quick look at skysurvey.Effect:

skysurvey.Effect object contains 2 parts:

1. a .model attribute that updates the Target’s model (DAG)

2. a sncosmo effect, with its variable name and the applied frame.

   • .effect: sncosmo.PropagationEffect

   • .name: str, the effect parameter name(s)

   • .frame: str, obs- or rest-frame

And that is all. When used, Effect.model will update the target model, while .effect, .name and .frame will be used to change the template.sncosmo model.

Get the Milky Way extinction Effect

The Milky way effect has been pre-defined (skysurvey.effect.mw_extinction) and works as follows:

1. mwebv is derived from the Planck dust map (dustmaps.planck) given the object’s RA, Dec so:

`model = {"mwebv": {"func": skysurvey.effect.milkyway.get_mwebv, "kwargs":{"ra":"@ra", "dec":"@dec"}}}`

2. The sncosmo effect is sncosmo.CCM89Dust() applied in the obsframe.

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Example

Draw SNe Ia without dust extinction (default)

import skysurvey

snia_no_dust = skysurvey.SNeIa.from_draw(1_000)
snia_no_dust.data.head(2)

	z	x1	c	t0	ra	dec	magabs	magobs	x0	template
0	0.18675	-2.195	0.123220	56144.281250	190.206924	12.827494	-18.770164	21.090797	0.000058	salt2
1	0.16555	0.295	0.004345	56033.667969	206.297791	65.779793	-19.359217	20.212688	0.000130	salt2

The object has no mwebv entry, and it’s template has no effect, so no mwebv in the parameter name

sncosmo_model = snia_no_dust.get_template(as_model=True)

sncosmo_model.effects

[]

snia_no_dust.template_parameters

['z', 't0', 'x0', 'x1', 'c']

Draw SNe Ia accounting for Milky Way dust extinction

from skysurvey import effects

snia = skysurvey.SNeIa.from_draw(1000, effect=effects.mw_extinction)

snia.data.head(2)

	z	x1	c	t0	ra	dec	magabs	mwebv	magobs	x0	template
0	0.17305	0.175	0.438834	56049.628906	351.960083	-39.255589	-17.934202	0.026303	21.743700	0.000032	salt2
1	0.01625	-0.735	0.045270	56095.554688	264.659637	-59.642555	-18.933451	0.143170	15.379986	0.011185	salt2

The object now has a mwebv entry that is connected to the RA and Dec

snia.model.visualize()

sncosmo_model = snia.get_template(as_model=True)
sncosmo_model.effects

[<sncosmo.models.CCM89Dust at 0x15eb2c880>]

snia.template_parameters

['z', 't0', 'x0', 'x1', 'c', 'mwebv', 'mwr_v']