PAHs as tracers of the molecular gas in star-forming galaxies

I. Cortzen; J. Garrett; G. Magdis; D. Rigopoulou; F. Valentino; M. Pereira-Santaella; F. Combes; A. Alonso-Herrero; S. Toft; E. Daddi; D. Elbaz; C. Gómez-Guijarro; M. Stockmann; J. Huang; C. Kramer

doi:10.1093/mnras/sty2777

PAHs as tracers of the molecular gas in star-forming galaxies

I. Cortzen, J. Garrett, G. Magdis, D. Rigopoulou, F. Valentino, M. Pereira-Santaella, F. Combes, A. Alonso-Herrero, S. Toft, E. Daddi, D. Elbaz, C. Gómez-Guijarro, M. Stockmann, J. Huang, C. Kramer

17 Citations (Scopus)

Abstract

We combine new CO(1-0) line observations of 24 intermediate redshift galaxies (0.03 < z < 0.28) along with literature data of galaxies at 0 < z < 4 to explore scaling relations between the dust and gas content using polycyclic aromatic hydrocarbon (PAH) 6.2 μm (L_6.2), CO (L'_CO), and infrared (L_IR) luminosities for a wide range of redshifts and physical environments. Our analysis confirms the existence of a universal L_6.2-L'_CO correlation followed by normal star-forming galaxies (SFGs) and starbursts (SBs) at all redshifts. This relation is also followed by local ultraluminous infrared galaxies that appear as outliers in the L_6.2-L_IR and L_IR-L'_CO relations defined by normal SFGs. The emerging tight (σ ≈ 0.26 dex) and linear (α = 1.03) relation between L_6.2 and L'_CO indicates α L_6.2 to molecular gas (MH₂ ) conversion factor of a6.2 = MH₂ /L_6.2 = (2.7 ± 1.3) × α_CO, where α_CO is the L'_CO to MH₂ conversion factor. We also find that on galaxy integrated scales, PAH emission is better correlated with cold rather than with warm dust emission, suggesting that PAHs are associated with the diffuse cold dust, which is another proxy for MH₂. Focusing on normal SFGs among our sample, we employ the dust continuum emission to derive MH₂ estimates and find a constant MH₂ /L_6.2 ratio of α_6.2 = 12.3 M_⊙/L_⊙(σ ≈ 0.3 dex). This ratio is in excellent agreement with the L'_CO-based MH₂ /L_6.2 values for α_CO = 4.5 M⊙/(K km s^-1 pc²) which is typical of normal SFGs. We propose that the presented L_6.2-L'_CO and L_6.2-MH₂ relations will serve as useful tools for the determination of the physical properties of high-z SFGs, for which PAH emission will be routinely detected by the James Webb Space Telescope.

Original language	English
Journal	Monthly Notices of the Royal Astronomical Society
Volume	482
Pages (from-to)	1618-1633
Number of pages	16
ISSN	0035-8711
DOIs	https://doi.org/10.1093/mnras/sty2777
Publication status	Published - 11 Jan 2019

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Cortzen, I., Garrett, J., Magdis, G., Rigopoulou, D., Valentino, F., Pereira-Santaella, M., Combes, F., Alonso-Herrero, A., Toft, S., Daddi, E., Elbaz, D., Gómez-Guijarro, C., Stockmann, M., Huang, J., & Kramer, C. (2019). PAHs as tracers of the molecular gas in star-forming galaxies. Monthly Notices of the Royal Astronomical Society, 482, 1618-1633. https://doi.org/10.1093/mnras/sty2777

Cortzen, I, Garrett, J, Magdis, G, Rigopoulou, D, Valentino, F, Pereira-Santaella, M, Combes, F, Alonso-Herrero, A, Toft, S, Daddi, E, Elbaz, D, Gómez-Guijarro, C, Stockmann, M, Huang, J & Kramer, C 2019, 'PAHs as tracers of the molecular gas in star-forming galaxies', Monthly Notices of the Royal Astronomical Society, vol. 482, pp. 1618-1633. https://doi.org/10.1093/mnras/sty2777

@article{86375b79c03040acb00ef833a5653a52,

title = "PAHs as tracers of the molecular gas in star-forming galaxies",

abstract = "We combine new CO(1-0) line observations of 24 intermediate redshift galaxies (0.03 < z < 0.28) along with literature data of galaxies at 0 < z < 4 to explore scaling relations between the dust and gas content using polycyclic aromatic hydrocarbon (PAH) 6.2 μm (L6.2), CO (L'CO), and infrared (LIR) luminosities for a wide range of redshifts and physical environments. Our analysis confirms the existence of a universal L6.2-L'CO correlation followed by normal star-forming galaxies (SFGs) and starbursts (SBs) at all redshifts. This relation is also followed by local ultraluminous infrared galaxies that appear as outliers in the L6.2-LIR and LIR-L'CO relations defined by normal SFGs. The emerging tight (σ ≈ 0.26 dex) and linear (α = 1.03) relation between L6.2 and L'CO indicates α L6.2 to molecular gas (MH2 ) conversion factor of a6.2 = MH2 /L6.2 = (2.7 ± 1.3) × αCO, where αCO is the L'CO to MH2 conversion factor. We also find that on galaxy integrated scales, PAH emission is better correlated with cold rather than with warm dust emission, suggesting that PAHs are associated with the diffuse cold dust, which is another proxy for MH2. Focusing on normal SFGs among our sample, we employ the dust continuum emission to derive MH2 estimates and find a constant MH2 /L6.2 ratio of α6.2 = 12.3 M⊙/L⊙(σ ≈ 0.3 dex). This ratio is in excellent agreement with the L'CO-based MH2 /L6.2 values for αCO = 4.5 M⊙/(K km s-1 pc2) which is typical of normal SFGs. We propose that the presented L6.2-L'CO and L6.2-MH2 relations will serve as useful tools for the determination of the physical properties of high-z SFGs, for which PAH emission will be routinely detected by the James Webb Space Telescope.",

keywords = "galaxies: active, galaxies: evolution, galaxies: ISM, galaxies: star formation",

author = "I. Cortzen and J. Garrett and G. Magdis and D. Rigopoulou and F. Valentino and M. Pereira-Santaella and F. Combes and A. Alonso-Herrero and S. Toft and E. Daddi and D. Elbaz and C. G{\'o}mez-Guijarro and M. Stockmann and J. Huang and C. Kramer",

year = "2019",

month = jan,

day = "11",

doi = "10.1093/mnras/sty2777",

language = "English",

volume = "482",

pages = "1618--1633",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

}

TY - JOUR

T1 - PAHs as tracers of the molecular gas in star-forming galaxies

AU - Cortzen, I.

AU - Garrett, J.

AU - Magdis, G.

AU - Rigopoulou, D.

AU - Valentino, F.

AU - Pereira-Santaella, M.

AU - Combes, F.

AU - Alonso-Herrero, A.

AU - Toft, S.

AU - Daddi, E.

AU - Elbaz, D.

AU - Gómez-Guijarro, C.

AU - Stockmann, M.

AU - Huang, J.

AU - Kramer, C.

PY - 2019/1/11

Y1 - 2019/1/11

N2 - We combine new CO(1-0) line observations of 24 intermediate redshift galaxies (0.03 < z < 0.28) along with literature data of galaxies at 0 < z < 4 to explore scaling relations between the dust and gas content using polycyclic aromatic hydrocarbon (PAH) 6.2 μm (L6.2), CO (L'CO), and infrared (LIR) luminosities for a wide range of redshifts and physical environments. Our analysis confirms the existence of a universal L6.2-L'CO correlation followed by normal star-forming galaxies (SFGs) and starbursts (SBs) at all redshifts. This relation is also followed by local ultraluminous infrared galaxies that appear as outliers in the L6.2-LIR and LIR-L'CO relations defined by normal SFGs. The emerging tight (σ ≈ 0.26 dex) and linear (α = 1.03) relation between L6.2 and L'CO indicates α L6.2 to molecular gas (MH2 ) conversion factor of a6.2 = MH2 /L6.2 = (2.7 ± 1.3) × αCO, where αCO is the L'CO to MH2 conversion factor. We also find that on galaxy integrated scales, PAH emission is better correlated with cold rather than with warm dust emission, suggesting that PAHs are associated with the diffuse cold dust, which is another proxy for MH2. Focusing on normal SFGs among our sample, we employ the dust continuum emission to derive MH2 estimates and find a constant MH2 /L6.2 ratio of α6.2 = 12.3 M⊙/L⊙(σ ≈ 0.3 dex). This ratio is in excellent agreement with the L'CO-based MH2 /L6.2 values for αCO = 4.5 M⊙/(K km s-1 pc2) which is typical of normal SFGs. We propose that the presented L6.2-L'CO and L6.2-MH2 relations will serve as useful tools for the determination of the physical properties of high-z SFGs, for which PAH emission will be routinely detected by the James Webb Space Telescope.

AB - We combine new CO(1-0) line observations of 24 intermediate redshift galaxies (0.03 < z < 0.28) along with literature data of galaxies at 0 < z < 4 to explore scaling relations between the dust and gas content using polycyclic aromatic hydrocarbon (PAH) 6.2 μm (L6.2), CO (L'CO), and infrared (LIR) luminosities for a wide range of redshifts and physical environments. Our analysis confirms the existence of a universal L6.2-L'CO correlation followed by normal star-forming galaxies (SFGs) and starbursts (SBs) at all redshifts. This relation is also followed by local ultraluminous infrared galaxies that appear as outliers in the L6.2-LIR and LIR-L'CO relations defined by normal SFGs. The emerging tight (σ ≈ 0.26 dex) and linear (α = 1.03) relation between L6.2 and L'CO indicates α L6.2 to molecular gas (MH2 ) conversion factor of a6.2 = MH2 /L6.2 = (2.7 ± 1.3) × αCO, where αCO is the L'CO to MH2 conversion factor. We also find that on galaxy integrated scales, PAH emission is better correlated with cold rather than with warm dust emission, suggesting that PAHs are associated with the diffuse cold dust, which is another proxy for MH2. Focusing on normal SFGs among our sample, we employ the dust continuum emission to derive MH2 estimates and find a constant MH2 /L6.2 ratio of α6.2 = 12.3 M⊙/L⊙(σ ≈ 0.3 dex). This ratio is in excellent agreement with the L'CO-based MH2 /L6.2 values for αCO = 4.5 M⊙/(K km s-1 pc2) which is typical of normal SFGs. We propose that the presented L6.2-L'CO and L6.2-MH2 relations will serve as useful tools for the determination of the physical properties of high-z SFGs, for which PAH emission will be routinely detected by the James Webb Space Telescope.

KW - galaxies: active, galaxies: evolution, galaxies: ISM, galaxies: star formation

U2 - 10.1093/mnras/sty2777

DO - 10.1093/mnras/sty2777

M3 - Journal article

SN - 0035-8711

VL - 482

SP - 1618

EP - 1633

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

ER -

PAHs as tracers of the molecular gas in star-forming galaxies

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