J/MNRAS/507/6177 PAHs bands in starburst-dominated galaxies (Canelo+, 2021)
Profile comparison of the 6-9 µm polycyclic aromatic hydrocarbon bands in
starburst-dominated galaxies.
Canelo C.M., Sales D.A., Friaca A.C.S., Pastoriza M., Menendez-Delmestre K.
<Mon. Not. R. Astron. Soc. 507, 6177-6195 (2021)>
=2021MNRAS.507.6177C 2021MNRAS.507.6177C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; H II regions ; Galaxies, IR ;
Infrared sources ; QSOs ; Star Forming Region ;
Galaxies, Seyfert ; References ; Redshifts ; Spectroscopy ;
Photometry ; Line Profiles ; Molecular data ;
Photometry, classification
Keywords: galaxies: ISM - infrared: galaxies - ISM: molecules - astrochemistry -
astrobiology
Abstract:
Polycyclic aromatic hydrocarbons (PAHs) are of great astrochemical and
astrobiological interest due to their potential to form prebiotic
molecules. We analyse the 7.7 and 8.6µm PAH bands in 126
pre-dominantly starburst- dominated galaxies extracted from the
Spitzer/IRS ATLAS project. Based on the peak positions of these bands,
we classify them into the different A, B, and C Peeters' classes,
which allows us to address the potential characteristics of the
PAH-emitting population. We compare this analysis with previous work
focused on the 6.2µm PAH band for the same sample. For the first
time in the literature, this statistical analysis is performed on a
sample of galaxies. In our sample, the 7.7µm complex is equally
distributed in A and B object's class while the 8.6µm band presents
more class B sources. Moreover, 39 per cent of the galaxies were
distributed into A class objects for both 6.2 and 7.7 µm bands and
only 18 per cent received the same A classification for the three
bands. The 'A A A' galaxies presented higher temperatures and less
dust in their interstellar medium. Considering the redshift range
covered by our sample, the distribution of the three bands into the
different Peeters' classes reveals a potential cosmological evolution
in the molecular nature of the PAHs that dominate the interstellar
medium in these galaxies, where B class objects seem to be more
frequent at higher redshifts and, therefore, further studies have to
be addressed.
Description:
In this sense, the analysis of the 6.2, 7.7, and 8.6µm bands could
reveal an overview of the physical and chemical conditions of the
sources, and also the potential presence of PAHNs molecules due to the
kind of astrophysical environments.In addition, the advantage of this
kind of study provides important insights to the behaviour of PAH
molecules through the ISM galaxy evolution in the Universe.
With this in mind, we here analyse and classify the 7.7 and 8.6µm
features of 126 galaxies observed with the Spitzer telescope according
to the Peeters' classes. We also compare the results with the
previous study of the 6.2µm band performed by Canelo et al.
(2018MNRAS.475.3746C 2018MNRAS.475.3746C). We present here for the first time a
statistical analysis on PAH profiles based on a sample of
extragalactic sources.
Starburst galaxies are ideal targets for PAH studies, since they carry
different bursts of young stellar populations and, consequently,
present strong PAH emission in the MIR spectral wavelengths,
particularly in the 6-9µm region. the same data sample was
considered (hereafter, MIR_SB sample). It is a sub-sample originally
extracted from the ATLAS MIR starburst-dominated galaxies sample of
the Spitzer/IRS ATLAS project1 Hernan-Caballero & Hatziminaoglou
(2011MNRAS.414..500H 2011MNRAS.414..500H, Cat. J/MNRAS/414/500) which possesses spectra of
several types of extragalactic objects.
The sources were observed in low resolution by the Infrared
Spectrograph (IRS; Houck et al. 2004ApJS..154...18H 2004ApJS..154...18H) of the Spitzer
Space Telescope (Werner et al. 2004) and their reduced spectra were
extracted. From the 155 sources used by Canelo et al.
(2018MNRAS.475.3746C 2018MNRAS.475.3746C), 29 objects present observational uncertainties
in the 7-9µm region much higher than those of the 6.2µm band,
probably due to its complexity, such as the blending bands in the
7.7µm complex. These uncertainties prevent the proper fitting of
the 7.7 and 8.6µm bands and a reliable analysis and comparison of
the results for these objects. These sources were removed from the our
original sample and 126 galaxies were studied in this work. Their
observationnal informations are available in the tablea1.dat,
(please see the section 2 Data selection).
After performing the continuum spectra substraction of these selected
galaxies (i.e section 3.1 Continuum subtraction), we proceed to
gaussian fitting of the PAH features in order to obtain spectroscopic
parameter such as monochromatic flux densities which leads us to
Peeters' classification (i.e section 3.2 Gaussian fit of the 7-9 µm
region. The tablec1 shows the raw results of these gaussian fits.
Likewise, the tablec2.dat assigns three monochromatic PAH fluxes for
each 126 selected galaxies which are better for fluxes comparison.
Then, in the tablec3.dat we respectively class each objects among
three Peeters' groups A,B, C explained in its description, (i.e table1
in the section 3.2 and further see section 4.2 Distribution into the
Peeters' classes).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 142 126 *Sources and their respective information
tablec1.dat 65 378 *Best-fitting results for the 7.7 and 8.6 µm
PAH bands
tablec2.dat 84 126 *Integrated flux intensities for the 6.2, 7.7,
and 8.6µm PAH bands
tablec3.dat 32 126 *Distribution of the galaxies into the Peeters'
classes for three PAH bands
--------------------------------------------------------------------------------
Note on tablea1.dat: As in Canelo et al. (2018MNRAS.475.3746C 2018MNRAS.475.3746C) sources are
extracted from the MIR_SB sample (Spitzer/IRS ATLAS, version 1.0) and
Yan et al. (2007ApJ...658..778Y 2007ApJ...658..778Y, Cat. J/ApJ/658/778).
Note on tablec1.dat and tablec2.dat: To study the PAH profile ofgalaxies, we
applied the same method used for the 6.2 µm band fitting
(Canelo et al. 2018MNRAS.475.3746C 2018MNRAS.475.3746C) in the 7.6, 7.8 and 8.6 µm features.
We constructed a python-based script to estimate their central wavelength,
amplitude and FWHM through the optimization algorithms from the submodule
scipy.optmize.curve_fit. The central wavelength, amplitude, and FWHM
uncertainties were also derived by this tool with least-squares minimization
from the flux uncertainties provided by the ATLAS. The initial guesses for the
parameters were selected from Smith et al. (2007ApJ...656..770S 2007ApJ...656..770S,
Cat. J/ApJ/656/770).
Note on tablec3.dat: Peeters' classes taken from Peeters et al.
2002A&A...390.1089P 2002A&A...390.1089P.
--------------------------------------------------------------------------------
See also:
J/MNRAS/414/500 : Spitzer/IRS ATLAS project source (Hernan-Caballero+, 2011)
J/ApJ/658/778 : Spitzer mid-IR spectroscopy of z∼2 ULIRGs (Yan+, 2007)
J/ApJ/656/770 : Mid-IR spectrum of star-forming galaxies (Smith+, 2007)
J/ApJ/693/370 : 24um flux-limited sample of galaxies (Weedman+, 2009)
J/MNRAS/395/1695 : Spitzer mid-IR spectroscopy of LIRGs
(Hernan-Caballero+, 2009)
J/ApJ/701/1123 : MIR spectroscopic catalog of 150 galaxies (Dasyra+, 2009)
J/ApJ/653/127 : 9.7um silicate features in AGNs (Shi+, 2006)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- ID Object name identifier (ID)
28 A1 --- n_ID Objects with redshift obtained through the
IRS Spitzer spectrum (n_ID)
30- 41 A12 --- Type Objects type (1)
43-110 A68 --- Ref Literature reference (Reference)
112-113 I2 h RAh Right ascension (J2000)
115-116 I2 min RAm Right ascension (J2000)
118-122 F5.2 s RAs Right ascension (J2000)
124 A1 --- DE- Sign of declination (J2000)
125-126 I2 deg DEd Declination (J2000)
128-129 I2 arcmin DEm Declination (J2000)
131-135 F5.2 arcsec DEs Declination (J2000)
137-142 F6.4 --- z Redshift (z)
--------------------------------------------------------------------------------
Note (1): Objects type as follows:
AGN = Active galactic nucleus
FR-1 = Fanaroff-Riley Class I galaxy
HII = HII region
IRgal = Infrared galaxy
LINER = Low-ionization nuclear emission-line region
QSO = Quasi-stellar object
SB = Starburst galaxy
SMG = Submillimetre galaxy
Sy1 = Type 1 Seyfert galaxy
Sy1.5 = Type 1.5 Seyfert galaxy
Sy1.8 = Type 1.8 Seyfert galaxy
Sy1.9 = Type 1.9 Seyfert galaxy
Sy2 = Type 2 Seyfert galaxy
Sy3 = Type 3 Seyfert galaxy
ULIRG = Ultra-luminous infrared galaxy
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- ID Object name identifier (ID)
28- 32 F5.3 um Lambdac Central wavelength (λc)
34- 38 F5.3 um e_Lambdac Mean error of Lambdac (Errλc_)
40- 46 F7.3 mJy/sr A Monochromatic flux density amplitude
per unit solid angle (A)
48- 53 F6.3 mJy/sr e_A Mean error on A (Err_A)
55- 59 F5.3 um FWHM Full width at half-maximum (FWHM)
61- 65 F5.3 um e_FWHM Mean error of FWHM (Err_FWHM)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablec2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- ID Object name identifier (ID)
28- 34 F7.3 mJy/sr F6.2 Monochromatic flux density amplitude at
6.2 µm per unit solid angle (F6.2)
36- 40 F5.3 mJy/sr e_F6.2 Mean error on F6.2 (Err_F6.2)
42- 48 F7.3 mJy/sr F7.6 Monochromatic flux density amplitude at
7.6 µm per unit solid angle (F7.6)
50- 55 F6.3 mJy/sr e_F7.6 Mean error on F7.6 (Err_F7.6)
57- 63 F7.3 mJy/sr F7.8 Monochromatic flux density amplitude at
7.8 µm per unit solid angle (F7.8)
65- 70 F6.3 mJy/sr e_F7.8 Mean error on F7.8 (Err_F7.8)
72- 78 F7.3 mJy/sr F8.6 Monochromatic flux density amplitude at
8.6 µm per unit solid angle (F8.6)
80- 84 F5.3 mJy/sr e_F8.6 Mean error on F8.6 (F8.6)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablec3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 26 A26 --- ID Object name identifier (ID)
28 A1 --- 6.2um [A/B/C] Peeters' class for the 6.2µm
PAH feature (6.2um) (1)
30 A1 --- 7.7um [A/B/C] Peeters' class for the 7.6um 7.8um
PAH features (7.7um) (2)
32 A1 --- 8.6um [A/B] Peeters' class for the 8.6um
PAH feature (8.6um) (3)
--------------------------------------------------------------------------------
Note (1): Peeters' class for the 6.2µm PAH feature is made as follows:
A = if central wavelength λc < 6.23µm
B = if central wavelength 6.23µm < λc < 6.29µm
C = if central wavelength λc > 6.29µm
Note (2): Peeters' class for the 7.6µm 7.8µm PAH features is made
as follows:
A = if central wavelength λc ∼ 7.6µm and F7.6/F7.8 ≥ 1
B = if central wavelength λc ∼ 7.8µm and F7.6/F7.8 < 1
C = if central wavelength λc ∼ 8.22µm
Note (3): Peeters' class for the 8.6µm PAH feature is made as follows:
A = if central wavelength λc < 8.6µm
B = if central wavelength λc > 8.6µm
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 25-Jul-2024