J/A+A/697/A18 HCN/HCO+ ratio for AGN (Butterworth+, 2025)
A multi-scale investigation into the diagnostic potential of the HCN/HCO+ ratio
for active galactic nucleus and starburst activity in nearby galaxies.
Butterworth J., Viti S., Wang Y.
<Astron. Astrophys. 697, A18 (2025)>
=2025A&A...697A..18B 2025A&A...697A..18B (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Galaxies, nearby ; Radio lines
Keywords: astrochemistry - ISM: molecules - galaxies: active - galaxies: ISM -
galaxies: Seyfert - galaxies: starburst
Abstract:
The identification of AGN and SB regions in galaxies is crucial for
understanding the role of various physical processes in galaxy
evolution. Molecular line ratios, such as the HCN/HCO+ ratio, have
been proposed as potential tracers of these distinct environments.
This paper aims to assess the reliability of the HCN/HCO+ ratio, from
J=1-0 to J=4-3 transitions, as a diagnostic tool for
differentiating AGN and SB activity across a diverse sample of nearby
galaxies. We focus on evaluating the effect of spatial resolution on
the robustness of these ratios and investigate the underlying physical
conditions that drive observed variations.
We compile observations of HCN and HCO+ lines across multiple J
transitions from various sources, covering different galaxy types,
including Seyferts, starbursts, and (ultra-)luminous infrared galaxies
(U/LIRGs). The observations span spatial scales from cloud-sized
regions to kiloparsec scales. We analyse the behaviour of these ratios
at varying resolutions and employ non-LTE radiative transfer models to
infer the physical conditions that drive the observed ratios. We find
that the HCN/HCO+ ratio from higher J transitions can differentiate
between AGN and SB activity when observed at high spatial resolution.
This distinction occurs around unity. However, at lower resolutions,
contamination from multiple emission sources and beam averaging
effects destroy these distinctions. Modelling suggests that elevated
HCN/HCO+ ratios in AGN-dominated regions are largely driven by an
enhancement in HCN abundance relative to HCO+, likely due to
high-temperature chemistry or increased excitation. Our study confirms
that the HCN/HCO+ ratio, particularly of higher J transitions, can be
a reliable tracer of AGN versus SB activity if observations are
conducted at sufficiently high spatial resolution.
Description:
A table of the data used throughout this paper of HCN and HCO+ lines
at varying resolutions in multiple nearby galaxies. The naming system
given in the original paper have been given where appropriate. Given
spatial scales are merely estimates. In the case where only the ratio
was given in the original paper, a -- has been added in place.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
appena.dat 64 251 Data used throughout this paper of HCN and HCO+
lines at varying resolutions in multiple
nearby galaxies
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Byte-by-byte Description of file: appena.dat
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Bytes Format Units Label Explanations
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1- 5 I5 pc Scale Spatial Scale
7- 11 A5 --- Trans Transition
13- 23 A11 --- Inst Instrument
25- 30 A6 --- MType Galaxy Type (AGN, C, SB or ULIRG)
31- 37 F7.2 K.km/s IHCN ?=- HCN integrated intensity
40- 45 F6.2 K.km/s e_IHCN ? HCN integrated intensity error
47- 53 F7.2 K.km/s IHCO+ ?=- HCO+ integrated intensity
56- 61 F6.2 K.km/s e_IHCO+ ? HCO+ integrated intensity error
63- 64 I2 --- Ref Reference (1)
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Note (1): References as follows:
1 = Sliwa et al., 2017A&A...604A..22B 2017A&A...604A..22B
2 = Gracia-Carpio et al., 2008Ap&SS.313..331S 2008Ap&SS.313..331S
3 = Israel et al., 2023A&A...671A..59I 2023A&A...671A..59I
4 = Kawamuro et al., 2019PASJ...71...68K 2019PASJ...71...68K
5 = Sato et al., 2022A&A...660A..82S 2022A&A...660A..82S
6 = Tristram et al., 2022A&A...664A..14A 2022A&A...664A..14A
7 = Nishimura et al., 2024A&A...686A..48N 2024A&A...686A..48N
8 = Tan et al., 2018ApJ...860..165T 2018ApJ...860..165T
9 = Imanishi et al., 2023ApJ...950...75I 2023ApJ...950...75I
10 = Aladro et al., 2015A&A...579A..10R 2015A&A...579A..10R
11 = Krips et al., 2008ApJ...677..262K 2008ApJ...677..262K
12 = Butterworth et al., 2022A&A...667A.131B 2022A&A...667A.131B
13 = Garcia-Burillo et al., 2008Ap&SS.313..261G 2008Ap&SS.313..261G
14 = Garcia_Burillo et al., 2019A&A...632A..61G 2019A&A...632A..61G
15 = Imanishi et al., 2020ApJ...902...99I 2020ApJ...902...99I
16 = Hsieh et al., 2012ApJ...747...90H 2012ApJ...747...90H
17 = Izumi et al., 2013PASJ...65..100I 2013PASJ...65..100I
18 = Imanishi et al., 2013AJ....146...47I 2013AJ....146...47I
19 = Ueda et al., 2021ApJS..257...57U 2021ApJS..257...57U
20 = Audibert et al., 2021A&A...656A..60A 2021A&A...656A..60A
21 = Meier et al., 2015ApJ...801...63M 2015ApJ...801...63M
22 = Butterworth et al., 2024A&A...686A..31B 2024A&A...686A..31B
23 = Jimenex-Donaire et al., 2017MNRAS.466...49J 2017MNRAS.466...49J
24 = Zhang et al., 2014ApJ...784L..31Z 2014ApJ...784L..31Z
25 = Audibert et al., 2019A&A...632A..33A 2019A&A...632A..33A
26 = Miyamoto et al., 2017PASJ...69...83M 2017PASJ...69...83M
27 = Izumi et al., 2015ApJ...811...39I 2015ApJ...811...39I
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Acknowledgements:
J. Butterworth, jjbuk2307(at)gmail.com
(End) Patricia Vannier [CDS] 25-Mar-2025