Spectral Line Search

Spectral Line Search#

This example shows how to use dysh to search for spectral lines. Searches can be done for a user-specified frequency range or for the frequency axis of a Spectrum. You can use a remote query to Splatalogue or use local tables distributed with dysh.

First we show how to do a search using a SpectralLineSearch object, then using a Spectrum object.

Loading Modules#

We start by loading the modules we will use.

# These modules are required for this example.
from dysh.line import SpectralLineSearch
from dysh.spectra import Spectrum
from astropy import units as u

Example 1. Doing an online or local search with SpectralLineSearch#

SpectralLineSearch is a thin wrapper on top of astroquery.splatalogue.Splatalogue, with some additional conveniences for working in dysh and with GBT data. You search a catalog in a given frequency range, optionally narrow down to specific molecules, line strengths, energies, etc. The return object is an astropy Table. Below are a few example searches.

Do an online search for N2H+ lines between 80 and 400 GHz#

Online searching of Splatalogue is the default. Note in this example we use an initial space in the chemical_name to eliminate other molecules that have the string 'N2H+' in them. We set an intensity_lower_limit to weed out some of the weaker satellite lines. When giving an intensity_lower_limit, one must also provide an intensity_type string, a minimum match to 'CDMS/JPL (log)', 'Sij-mu2', or 'Aij (log)'.

minfreq = 80*u.GHz
maxfreq = 400*u.GHz
table = SpectralLineSearch.query_lines(minfreq, maxfreq, 
                                       chemical_name=" N2H+", 
                                       intensity_lower_limit=-3, 
                                       intensity_type="CDMS")

print(f"{len(table)} rows returned.")

57 rows returned.

To inspect the available columns use the Table.colnames attribute:

print(table.colnames)

['species_id', 'name', 'chemical_name', 'resolved_QNs', 'linelist', 'LovasASTIntensity', 'lower_state_energy', 'upper_state_energy', 'sijmu2', 'sij', 'aij', 'intintensity', 'Lovas_NRAO', 'orderedfreq', 'lower_state_energy_K', 'upper_state_energy_K', 'upperStateDegen', 'moleculeTag', 'qnCode', 'labref_Lovas_NIST', 'rel_int_HFS_Lovas', 'unres_quantum_numbers', 'lineid', 'transition_in_space', 'transition_in_G358', 'obsref_Lovas_NIST', 'source_Lovas_NIST', 'telescope_Lovas_NIST', 'searchErrorMessage']

The orderedfreq column is the rest frequency of the transition in MHz.

Some columns in the table often have embedded HTML. That’s the way they come from Splatalogue. ¯\_(ツ)_/¯

table

Table length=57

species_id	name	chemical_name	resolved_QNs	linelist	LovasASTIntensity	lower_state_energy	upper_state_energy	sijmu2	sij	aij	intintensity	Lovas_NRAO	orderedfreq	lower_state_energy_K	upper_state_energy_K	upperStateDegen	moleculeTag	qnCode	labref_Lovas_NIST	rel_int_HFS_Lovas	unres_quantum_numbers	lineid	transition_in_space	transition_in_G358	obsref_Lovas_NIST	source_Lovas_NIST	telescope_Lovas_NIST	searchErrorMessage
int64	str57	str11	str44	str4	str4	float64	float64	float64	float64	float64	float64	int64	float64	float64	float64	str2	int64	int64	str1	str1	str18	int64	int64	int64	str6	str8	str13	str1
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 1 - 0, F<sub>1</sub>= 1- 1	JPL	0.8	0.0	3.10788	37.25038	3.222	-4.40932	-2.7844	1	93171.88	0.0	4.47152	9	-29005	102			J=1-0-F1=1-1	830340	1	0	Cas95	L134N	NRAO 11m
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J = 1 - 0	CDMS		0.0	3.10793	104.04257	0.0	-4.44034	-2.3383	1	93173.3977	0.0	4.47165	27	29506	101			1 0	14632649	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 1 - 0, F<sub>1</sub>= 2- 1	JPL	0.6	0.0	3.10794	62.08887	5.371	-4.40926	-2.5625	1	93173.7	0.0	4.47161	15	-29005	102			J=1-0-F1=2-1	830341	1	0	Cas95	L134N	NRAO 11m
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 1- 0,F<sub>1</sub>= 2- 1,F= 3- 2	CDMS		0.0	3.10794	26.97166	0.0	-4.44038	-2.9246	1	93173.7699	0.0	4.47166	7	29506	103			1 2 3 0 1 2	14632704	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 2- 1,F<sub>1</sub>= 2- 2,F= 3- 3	CDMS		3.1079	9.32363	8.12394	0.0	-4.05846	-2.8534	1	186342.9249	4.4716	13.41471	7	29506	103			2 2 3 1 2 3	14632714	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 2- 1,F<sub>1</sub>= 1- 0,F= 1- 1	CDMS		3.108	9.32374	7.46735	0.0	-3.72708	-2.89	1	186343.0616	4.47175	13.41486	3	29506	103			2 1 1 1 0 1	14632716	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 2- 1,F<sub>1</sub>= 1- 0,F= 2- 1	CDMS		3.108	9.32374	12.86961	0.0	-3.71253	-2.6536	1	186343.2691	4.47175	13.41487	5	29506	103			2 1 2 1 0 1	14632718	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 2- 1,F<sub>1</sub>= 2- 1,F= 2- 1	CDMS		3.1079	9.32368	13.81529	0.0	-3.68173	-2.6228	1	186344.3941	4.4716	13.41478	5	29506	103			2 2 2 1 1 1	14632721	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J = 2 - 1	CDMS		3.1079	9.32369	208.09363	0.0	-3.45807	-1.4449	1	186344.6844	4.4716	13.4148	45	29506	101			2 1	14632650	0	0
...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J=4-3	JPL		18.6472	31.07822	446.71817	38.6	-2.47854	-0.5499	1	372672.509	26.82901	44.71436	81	-29005	101			J=4-3	830345	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 4- 3,F= 5- 4	CDMS		18.6472	31.07822	52.55677	0.0	-2.54085	-1.4793	1	372672.5116	26.82934	44.71491	11	29506	103			4 4 5 3 3 4	14632777	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 5- 4,F= 4- 3	CDMS		18.6473	31.07832	43.69471	0.0	-2.5339	-1.5595	1	372672.5164	26.82948	44.71506	9	29506	103			4 5 4 3 4 3	14632778	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 5- 4,F= 5- 4	CDMS		18.6472	31.07822	54.59196	0.0	-2.52435	-1.4628	1	372672.5228	26.82934	44.71491	11	29506	103			4 5 5 3 4 4	14632779	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 5- 4,F= 6- 5	CDMS		18.6472	31.07822	66.79264	0.0	-2.5093	-1.3752	1	372672.5535	26.82934	44.71491	13	29506	103			4 5 6 3 4 5	14632780	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 3- 2,F= 2- 2	CDMS		18.6473	31.07833	4.11461	0.0	-3.30472	-2.5856	1	372672.8201	26.82948	44.71507	5	29506	103			4 3 2 3 2 2	14632781	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 4- 3,F= 3- 3	CDMS		18.6472	31.07823	2.04187	0.0	-3.75515	-2.8899	1	372672.9213	26.82934	44.71493	7	29506	103			4 4 3 3 3 3	14632782	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 5- 4,F= 4- 4	CDMS		18.6472	31.07823	2.4959	0.0	-3.7771	-2.8027	1	372673.028	26.82934	44.71494	9	29506	103			4 5 4 3 4 4	14632783	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 3- 3,F= 3- 3	CDMS		18.6472	31.07829	3.04385	0.0	-3.58175	-2.7165	1	372674.846	26.82934	44.71502	7	29506	103			4 3 3 3 3 3	14632786	0	0
148	N<sub>2</sub>H<sup>+</sup> <font color="red">v = 0</font>	Diazenylium	J= 4- 3,F<sub>1</sub>= 3- 3,F= 4- 4	CDMS		18.6472	31.0783	3.23387	0.0	-3.66459	-2.6902	1	372674.9101	26.82934	44.71503	9	29506	103			4 3 4 3 3 4	14632787	0	0

Do a local search for methyl formate.#

This uses a GBT-specific catalog distributed with dysh. You can also provide your own catalog in an astropy Table format. The first time you use a given catalog, there will be some additional overhead to read it in and cache it. Subsequent searches will be faster because they use the cached version. Note the default regular expression matching is case-insensitive. The gbtlines catalog has most lines from 300 MHz to 120 GHz, and commonly observed redshifted lines from 120 GHz to 5 THz.

minfreq = 400*u.MHz
maxfreq = 5550*u.MHz
table = SpectralLineSearch.query_lines(minfreq, maxfreq,
                                       cat='gbtlines', 
                                       chemical_name="methyl formate")

print(f"{len(table)} rows returned.")

48 rows returned.

table

Table length=48

species_id	name	chemical_name	resolved_QNs	linelist	LovasASTIntensity	lower_state_energy	upper_state_energy	sijmu2	sij	aij	intintensity	Lovas_NRAO	orderedfreq	lower_state_energy_K	upper_state_energy_K	upperStateDegen	moleculeTag	qnCode	labref_Lovas_NIST	rel_int_HFS_Lovas	unres_quantum_numbers	lineid	transition_in_space	transition_in_G358	obsref_Lovas_NIST	source_Lovas_NIST	telescope_Lovas_NIST	searchErrorMessage
int64	str47	str14	str44	str6	bytes1	float64	float64	float64	float64	float64	float64	int64	float64	float64	float64	str3	int64	int64	str5	bytes1	str20	int64	int64	int64	bytes1	bytes1	bytes1	bytes1
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	1(1, 0) - 1(1, 1), v<sub>t</sub> = 0 - 0, A	ToyaMA	--	0.9	0.95371	0.0	0.0	0.0	0.03537	0	1610.249	1.29491	1.37219	--	0	0	Brown	--	--	10692427	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	1(1, 0) - 1(1, 1), v<sub>t</sub> = 0 - 0, E	ToyaMA	--	0.9	0.95373	0.0	0.0	0.0	0.03537	0	1610.906	1.29491	1.37222	--	0	0	Brown	--	--	10692428	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	27( 8,19)-27( 8,20) A	JPL	--	185.6381	185.70448	10.70843	0.0	-10.74808	--	1	1990.0988	267.09028	267.18579	110	60003	1404	--	--	27 819 0 27 820 0	11416364	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	11( 4, 7)-11( 4, 8) A	JPL	--	34.5439	34.61039	6.89492	0.0	-10.55855	--	1	1993.2922	49.70068	49.79634	46	60003	1404	--	--	11 4 7 0 11 4 8 0	11416365	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	4( 2, 2)- 4( 2, 3) A	JPL	--	5.9236	5.99132	4.62746	0.0	-10.30044	--	1	2030.0631	8.52269	8.62012	18	60003	1404	--	--	4 2 2 0 4 2 3 0	11416366	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	23( 7,16)-23( 7,17) A	JPL	--	136.5469	136.61859	9.7273	0.0	-10.62136	--	1	2149.165	196.4594	196.56254	94	60003	1404	--	--	23 716 0 23 717 0	11416367	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	15( 5,10)-15( 5,11) A	JPL	--	60.9946	61.06816	7.80019	0.0	-10.50287	--	1	2205.377	87.75712	87.86296	62	60003	1404	--	--	15 510 0 15 511 0	11416368	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	19( 6,13)-19( 6,14) A	JPL	--	94.997	95.0716	8.75245	0.0	-10.53441	--	1	2236.3094	136.67871	136.78603	78	60003	1404	--	--	19 613 0 19 614 0	11416369	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	36(10,26)-36(10,27) A	JPL	--	321.4598	321.54727	12.03857	0.0	-10.46084	--	1	2622.1518	462.50629	462.63213	146	60003	1404	--	--	361026 0 361027 0	11416370	0	0	--	--	--	--
...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
1333	CH<sub>3</sub>OCHO<font color="red"> v=1</font>	Methyl Formate	38(10,28)-38(10,29) A	JPL	--	480.8501	481.00845	10.95698	0.0	-9.75158	--	0	4747.0995	691.83205	692.05988	154	60003	1404	--	--	381028 3 381029 3	11416400	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	46(12,34)-46(12,35) A	JPL	--	513.7385	513.8993	12.72518	0.0	-9.7486	--	1	4820.5148	739.15085	739.3822	186	60003	1404	--	--	461234 0 461235 0	11416401	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	2( 1, 1)- 2( 1, 2) E	JPL	--	1.6184	1.77944	2.21444	0.0	-9.23648	--	1	4827.9657	2.3285	2.56021	10	60003	1404	--	--	2 1 1 2 2 1 2 1	11416402	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	2( 1, 1)- 2( 1, 2) A	JPL	--	1.605	1.76613	2.21541	0.0	-9.23557	--	1	4830.6409	2.30922	2.54106	10	60003	1404	--	--	2 1 1 0 2 1 2 0	11416403	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	33( 9,24)-33( 9,25) E	JPL	--	269.4333	269.59659	10.37877	0.0	-9.67465	--	1	4895.3142	387.65219	387.88712	134	60003	1404	--	--	33 924 2 33 925 1	11416404	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	33( 9,24)-33( 9,25) A	JPL	--	269.4373	269.60088	10.38301	0.0	-9.67218	--	1	4903.9512	387.65794	387.89329	134	60003	1404	--	--	33 924 0 33 925 0	11416405	0	0	--	--	--	--
1333	CH<sub>3</sub>OCHO<font color="red"> v=1</font>	Methyl Formate	21( 6,15)-21( 6,16) A	JPL	--	241.7578	241.93224	7.49079	0.0	-9.53759	--	0	5229.6632	347.83355	348.08453	86	60003	1404	--	--	21 615 3 21 616 3	11416406	0	0	--	--	--	--
1333	CH<sub>3</sub>OCHO<font color="red"> v=1</font>	Methyl Formate	9( 3, 6)- 9( 3, 7) A	JPL	--	153.0547	153.23353	4.51676	0.0	-9.37024	--	0	5361.0499	220.21031	220.46759	38	60003	1404	--	--	9 3 6 3 9 3 7 3	11416407	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	29( 8,21)-29( 8,22) E	JPL	--	209.4473	209.63205	9.38377	0.0	-9.50232	--	1	5538.6728	301.34621	301.61202	118	60003	1404	--	--	29 821 2 29 822 1	11416408	0	0	--	--	--	--
393	CH<sub>3</sub>OCHO <font color="red">v=0</font>	Methyl Formate	29( 8,21)-29( 8,22) A	JPL	--	209.4498	209.63489	9.38565	0.0	-9.49981	--	1	5549.0032	301.34981	301.61612	118	60003	1404	--	--	29 821 0 29 822 0	11416409	0	0	--	--	--	--

Search for Recombination Lines#

dysh has special methods to search for recombination lines of Hydrogen, Helium, and Carbon. SpectralLineSearch.recomb will search for a specific atom/transition, while SpectralLineSearch.recomball will search for all three species.

minfreq = 300*u.MHz
maxfreq = 2.0*u.GHz
table = SpectralLineSearch.recomb(minfreq, maxfreq,
                                  cat='gbtrecomb',
                                  line="Hebeta")

table

Table length=165

species_id	name	chemical_name	resolved_QNs	linelist	LovasASTIntensity	lower_state_energy	upper_state_energy	sijmu2	sij	aij	intintensity	Lovas_NRAO	orderedfreq	lower_state_energy_K	upper_state_energy_K	upperStateDegen	moleculeTag	qnCode	labref_Lovas_NIST	rel_int_HFS_Lovas	unres_quantum_numbers	lineid	transition_in_space	transition_in_G358	obsref_Lovas_NIST	source_Lovas_NIST	telescope_Lovas_NIST	searchErrorMessage
int64	str8	str25	str17	str6	bytes1	float64	float64	float64	float64	float64	float64	int64	float64	float64	float64	bytes1	int64	int64	bytes1	bytes1	str13	int64	int64	int64	bytes1	bytes1	bytes1	bytes1
1161	Heβ	Helium Recombination Line	He ( 351 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	301.685543664761	0.0	0.0	--	0	0	--	--	He(351)β	3956582	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 350 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	304.271433765971	0.0	0.0	--	0	0	--	--	He(350)β	3956581	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 349 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	306.886961777696	0.0	0.0	--	0	0	--	--	He(349)β	3956580	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 348 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	309.532553535472	0.0	0.0	--	0	0	--	--	He(348)β	3956579	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 347 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	312.20864223806103	0.0	0.0	--	0	0	--	--	He(347)β	3956578	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 346 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	314.915668596411	0.0	0.0	--	0	0	--	--	He(346)β	3956577	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 345 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	317.654080986085	0.0	0.0	--	0	0	--	--	He(345)β	3956576	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 344 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	320.42433560322803	0.0	0.0	--	0	0	--	--	He(344)β	3956575	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 343 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	323.226896624166	0.0	0.0	--	0	0	--	--	He(343)β	3956574	0	0	--	--	--	--
...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
1161	Heβ	Helium Recombination Line	He ( 196 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1721.07257030867	0.0	0.0	--	0	0	--	--	He(196)β	3956427	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 195 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1747.5510705209301	0.0	0.0	--	0	0	--	--	He(195)β	3956426	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 194 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1774.5755311558198	0.0	0.0	--	0	0	--	--	He(194)β	3956425	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 193 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1802.16009664062	0.0	0.0	--	0	0	--	--	He(193)β	3956424	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 192 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1830.31935342969	0.0	0.0	--	0	0	--	--	He(192)β	3956423	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 191 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1859.06834620505	0.0	0.0	--	0	0	--	--	He(191)β	3956422	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 190 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1888.42259475907	0.0	0.0	--	0	0	--	--	He(190)β	3956421	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 189 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1918.39811159176	0.0	0.0	--	0	0	--	--	He(189)β	3956420	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 188 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1949.01142025697	0.0	0.0	--	0	0	--	--	He(188)β	3956419	0	0	--	--	--	--
1161	Heβ	Helium Recombination Line	He ( 187 ) β	Recomb	--	0.0	0.0	0.0	0.0	0.0	--	1	1980.27957449351	0.0	0.0	--	0	0	--	--	He(187)β	3956418	0	0	--	--	--	--

Search all recombination lines. As with any astropy Table, you can limit the displayed columns with a list.

table = SpectralLineSearch.recomball(minfreq, maxfreq,
                                     cat='gbtrecomb')
table[['name', 'chemical_name', 'orderedfreq']]

Table length=2332

name	chemical_name	orderedfreq
str10	str27	float64
Hε	Hydrogen Recombination Line	300.134854181299
Hγ	Hydrogen Recombination Line	300.310962014245
Heγ	Helium Recombination Line	300.43333977202605
Cγ	Carbon Recombination Line	300.460803205189
Hδ	Hydrogen Recombination Line	300.536517272198
Heδ	Helium Recombination Line	300.65898694452807
Hα	Hydrogen Recombination Line	301.179832211236
Heα	Helium Recombination Line	301.30256403663304
Cα	Carbon Recombination Line	301.33010692796296
...	...	...
Cγ	Carbon Recombination Line	1972.4531543176602
Hδ	Hydrogen Recombination Line	1976.26579923329
Heδ	Helium Recombination Line	1977.0711343954397
Hβ	Hydrogen Recombination Line	1979.47293241347
Heβ	Helium Recombination Line	1980.27957449351
Cβ	Carbon Recombination Line	1980.46059726474
Hζ	Hydrogen Recombination Line	1982.9801715469202
Hε	Hydrogen Recombination Line	1995.0739903907402
Hγ	Hydrogen Recombination Line	1999.1730383073698
Heγ	Helium Recombination Line	1999.98770824883

Example 2. Search within the frequency range of a Spectrum#

The Spectrum.query_lines. Spectrum.recomb, and Spectrum.recomball methods of Spectrum will use the minimum and maximum frequencies of the spectral axis. Other keywords are the same as in SpectralLineSearch.

For this example we construct a fake spectrum, with 16384 channels that are 1 kHz wide and a rest frequency of 1.4240575 GHz.

cdelt1 = float((1000*u.Hz).value)
nchan = 16384
restfreq = float((1.4240575*u.GHz).to(u.Hz).value)
crval1 = restfreq
s = Spectrum.fake_spectrum(nchan=nchan, 
                           crval1=crval1, 
                           restfrq=restfreq, 
                           freqres=cdelt1, 
                           cdelt1=cdelt1, 
                           obsfreq=restfreq, 
                           dopfreq=restfreq, 
                           object='MyFakeSrc')

s.plot(vel_frame='icrs', xaxis_unit='km/s')

<dysh.plot.specplot.SpectrumPlot at 0x78714e72e5f0>

../../_images/ebfc36fc43ea7d21374bf601c70f19b7cebb53d471b507eefb2243ebdec09094.png

Find the hydrogen recombination lines that could be in this spectrum, and display their name, chemical name and frequency (in MHz).

s.recomb(line='hydrogen', cat='gbtrecomb')[['name', 'chemical_name', 'orderedfreq']]

Table length=6

name	chemical_name	orderedfreq
str10	str27	float64
Hγ	Hydrogen Recombination Line	1418.3334505418002
Hζ	Hydrogen Recombination Line	1418.65587364335
Hβ	Hydrogen Recombination Line	1420.2354594106603
Hα	Hydrogen Recombination Line	1424.73358996475
Hε	Hydrogen Recombination Line	1428.10062420283
Hδ	Hydrogen Recombination Line	1429.77140255287

Find all lines in the spectrum’s frequency range.

s.query_lines(cat='gbtlines')[['name', 'chemical_name', 'orderedfreq']].pprint_all()

                                  name                                    chemical_name     orderedfreq  
------------------------------------------------------------------------ ---------------- ---------------
                                                                  H-atom  Atomic Hydrogen 1420.4057517667
                                                               NaCN/NaNC   Sodium Cyanide       1430.0591
                                                                    17OH Hydroxyl radical       1418.1976
                                                                    17OD Hydroxyl radical       1419.1013
                                                                    17OD Hydroxyl radical       1419.5477
                                                                    17OD Hydroxyl radical        1420.094
                                                                   HDCCO           Ketene       1417.2492
                                                          ND<sub>3</sub>          Ammonia       1416.7226
                                                          ND<sub>3</sub>          Ammonia        1416.725
                                                          ND<sub>3</sub>          Ammonia        1417.696
                                                         NHD<sub>2</sub>          Ammonia       1417.8791
                                                          ND<sub>3</sub>          Ammonia        1423.215
                                                          ND<sub>3</sub>          Ammonia        1423.215
                                                          ND<sub>3</sub>          Ammonia        1423.215
                                                          ND<sub>3</sub>          Ammonia        1423.215
                                                          ND<sub>3</sub>          Ammonia        1425.106
                                           c-D<sub>2</sub>C<sub>3</sub>O   Cyclopropenone       1416.8873
<sup>13</sup>CH<sub>3</sub>OH <font color="red">v<sub>t</sub> = 1</font>         Methanol        1424.617
<sup>13</sup>CH<sub>3</sub>OH <font color="red">v<sub>t</sub> = 1</font>         Methanol        1424.617
                           <i>gauche</i>-CH<sub>2</sub>DCH<sub>2</sub>CN    Ethyl Cyanide       1419.4688
                             CH<sub>3</sub>CH<sub>2</sub><sup>13</sup>CN    Ethyl Cyanide       1425.1485
                             CH<sub>3</sub>CH<sub>2</sub><sup>13</sup>CN    Ethyl Cyanide       1425.1695
                             CH<sub>3</sub>CH<sub>2</sub><sup>13</sup>CN    Ethyl Cyanide       1425.3982
                             CH<sub>3</sub>CH<sub>2</sub><sup>13</sup>CN    Ethyl Cyanide       1425.4355
                                                        CH<sub>2</sub>CN      Cyanomethyl       1430.3244
                                                              c-HC(O)NHD        Formamide       1430.3802

To clear the cache, use:

SpectralLineSearch.clear_cache()