scholarly journals Polycyclic aromatic hydrocarbon excitation in nearby spiral galaxies

2020 ◽  
Vol 496 (2) ◽  
pp. 1393-1417 ◽  
Author(s):  
G J Bendo ◽  
N Lu ◽  
A Zijlstra
Keyword(s):  
Star Formation ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Spiral Galaxies ◽  
Dust Emission ◽  
Stellar Populations ◽  
Mid Infrared ◽  
Star Forming ◽  
Evolved Stars ◽  
Polycyclic Aromatic

ABSTRACT We have examined polycyclic aromatic hydrocarbon (PAH) excitation in a sample of 25 nearby face-on spiral galaxies using the ratio of mid-infrared PAH emission to dust mass. Within 11 of the galaxies, we found that the PAH excitation was straightforwardly linked to ultraviolet (UV) or mid-infrared star formation tracers, which, along with other results studying the relation of PAH emission to star formation, indicates that the PAHs are most strongly excited in dusty shells around the star-forming (SF) regions. Within another five galaxies, the PAH emission is enhanced around SF regions only at specific galactocentric radii. In six more galaxies, PAH excitation is more strongly correlated with the evolved stellar populations as traced by 3.6 μm emission. The results for the remaining three galaxies were ambiguous. The radial gradients of the PAH/dust ratios were generally not linked to log(O/H) gradients except when the log(O/H) gradients were relatively steep. Galaxies in which PAHs were excited by evolved stars had relatively high far-UV to mid-infrared ratios, implying that variations in the link between PAH excitation and different stellar populations are connected to changes in dust attenuation within galaxies. Alternately, differences in morphology could make it more likely that PAHs are excited by evolved stars, as five of the six galaxies where this occurs are late-type flocculent spiral galaxies. These heterogeneous results demonstrate the complexity of describing PAH excitation and have broad implications for using PAH emission as a star formation tracer as well as for modelling dust emission and radiative transfer.

Mid-infrared PAH emission from star-forming galaxies selected at 250 μm

2019 ◽  
Vol 15 (S341) ◽  
pp. 281-282
Author(s):  
Seong Jin Kim ◽  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Physical Modeling ◽  
Wide Field ◽  
Mid Infrared ◽  
Star Forming ◽  
Polycyclic Aromatic ◽  
Data Points ◽  
Cold Dust ◽  
Strong Radiation

AbstractThe infrared (IR) galaxies detected at Herschel/SPIRE 250 μm band over the AKARI’s NEP-Wide field are various types of dusty star-forming (SF) galaxies ranging from quiescent to starbursts, having mid-IR polycyclic aromatic hydrocarbon (PAH) features near 8 μm. The measurements of the 8 μm luminosity (L8μm) along with the total infrared luminosity (LIR) based on the physical modeling of SEDs a take unique advantage of the continuous near- to mid-IR coverage, far-IR data points, and spectroscopically determined accurate redshifts. Our sample shows shortage of 8 μm luminosity compared to the total IR luminosity. This deficit gets severe in more luminous IR galaxies, suggesting PAH molecules in these galaxies are destroyed by a strong radiation field from SF regions, or the existence of a unexpectedly large amount of cold dust in the ISM that contributes to LIR.

The properties of the dusty inner regions of nearby QSOs

2019 ◽  
Vol 15 (S356) ◽  
pp. 95-95
Author(s):  
Itziar Aretxaga
Keyword(s):  
Star Formation ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Stellar Objects ◽  
X Ray ◽  
Mir Spectroscopy ◽  
Polycyclic Aromatic ◽  
Quasi Stellar Objects

AbstractWe present MIR spectroscopy and photometry obtained with CanariCam on the 10.4 m Gran Telescopio CANARIAS for a sample of 20 nearby, MIR bright and X-ray luminous quasi-stellar objects (QSOs). We find that for the majority of QSOs the MIR emission is unresolved at angular scales ∼0.3 arcsec. We derive the properties of the dusti tori that surround the nucleus based on these observations and find significant differences in the parameters compared with a sample of Seyfert 1 and 2 nuclei. We also find evidence for polycyclic aromatic hydrocarbon (PAH) features in the spectra, indicative of star formation, more centrally peaked (on scales of a few hundred pc) than previously believed.

scholarly journals Mid‐Infrared and Visible Photometry of Galaxies: Anomalously Low Polycyclic Aromatic Hydrocarbon Emission from Low‐Luminosity Galaxies

2005 ◽  
Vol 624 (1) ◽  
pp. 162-167 ◽  
Author(s):  
David W. Hogg ◽  
Christy A. Tremonti ◽  
Michael R. Blanton ◽  
Douglas P. Finkbeiner ◽  
Nikhil Padmanabhan ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Mid Infrared ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
Polycyclic Aromatic Hydrocarbon Emission

scholarly journals The Spitzer spectroscopic survey of the Small Magellanic Cloud: polycyclic aromatic hydrocarbon emission from SMC star-forming regions

2008 ◽  
Vol 4 (S256) ◽  
pp. 160-165
Author(s):  
Karin M. Sandstrom ◽  
Alberto D. Bolatto ◽  
Snežana Stanimirović ◽  
J. D. T. Smith ◽  
Jacco Th. van Loon ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Physical State ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
Low Metallicity

AbstractBecause of its proximity, the Small Magellanic Cloud provides a unique opportunity to map the polycyclic aromatic hydrocarbon (PAH) emission from photo-dissociation regions (PDRs) in a low-metallicity (12 + log(O/H) ~ 8) galaxy at high spatial resolution in order to learn about their abundance and physical state. We present mid-IR spectral mapping observations of star-forming regions in the Small Magellanic Cloud obtained as part of the Spitzer Spectroscopic Survey of the SMC (S4MC) project. These observations allow us to map the distribution of PAH emission in these regions and the measure the variation of PAH band strengths with local physical conditions. In these proceedings we discuss preliminary results on the physical state of the PAHs, in particular their ionization fraction.

scholarly journals SDSS-IV MaNGA: spatially resolved dust attenuation in spiral galaxies

2020 ◽  
Vol 495 (2) ◽  
pp. 2305-2320
Author(s):  
Michael J Greener ◽  
Alfonso Aragón-Salamanca ◽  
Michael R Merrifield ◽  
Thomas G Peterken ◽  
Amelia Fraser-McKelvie ◽  
...  
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Formation Rate ◽  
Stellar Populations ◽  
High Concentration ◽  
Full Spectrum ◽  
Star Forming ◽  
Spatially Resolved ◽  
Radial Profiles ◽  
Dust Attenuation

ABSTRACT Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, derived from spectra acquired by the SDSS-IV MaNGA survey. The dust attenuation affecting the stellar populations of these galaxies (obtained using full spectrum stellar population fitting methods) is compared with the dust attenuation in the gas (derived from the Balmer decrement). Both of these attenuation measures increase for local regions of galaxies with higher star formation rates; the dust attenuation affecting the stellar populations increases more so than the dust attenuation in the gas, causing the ratio of the dust attenuation affecting the stellar populations to the dust attenuation in the gas to decrease for local regions of galaxies with higher star formation rate densities. No systematic difference is discernible in any of these dust attenuation quantities between the spiral arm and interarm regions of the galaxies. While both the dust attenuation in the gas and the dust attenuation affecting the stellar populations decrease with galactocentric radius, the ratio of the two quantities does not vary with radius. This ratio does, however, decrease systematically as the stellar mass of the galaxy increases. Analysis of the radial profiles of the two dust attenuation measures suggests that there is a disproportionately high concentration of birth clouds (incorporating gas, young stars, and clumpy dust) nearer to the centres of star-forming spiral galaxies.

scholarly journals Mid-IR Spectroscopy of Submm Galaxies: Extended Star Formation in High-z Galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 423-424
Author(s):  
K. Menéndez-Delmestre ◽  
A. W. Blain ◽  
I. Smail ◽  
D. M. Alexander ◽  
S. C. Chapman ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Dust Emission ◽  
Infrared Galaxies ◽  
Local Universe ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Formation Activity ◽  
Polycyclic Aromatic ◽  
Intense Star Formation

AbstractUltra-luminous infrared galaxies (ULIRGs; L > 1012 L⊙) are quite rare in the local universe, but seem to dominate the co-moving energy density at z > 2. Many are optically-faint, dust-obscured galaxies that have been identified only relatively recently by the detection of their thermal dust emission redshifted into the sub-mm wavelengths. These submm galaxies (SMGs) have been shown to be a massive objects (M* ~ 1011 M⊙) undergoing intense star-formation(SFRs ~ 102 − 103 M⊙ yr−1) and the likely progenitors of massive ellipticals today. However, the AGN contribution to the far-IR luminosity had for years remained a caveat to these results. We used the Spitzer Infrared Spectrograph (IRS) to investigate the energetics of 24 radio-identified and spectroscopically-confirmed SMGs in the redshift range of 0.6 < z < 3.2. We find emission from Polycyclic Aromatic Hydrocarbons (PAHs) – which are associated with intense star-formation activity – in >80% of our sample and find that the median mid-IR spectrum is well described by a starburst component with an additional power-law continuum representing < 32% AGN contribution to the far-IR luminosity. We also find evidence for a more extended distribution of warm dust in SMGs compared to the more compact nuclear bursts in local ULIRGs and starbursts, suggesting that SMGs are not simple high-redshift analogs of local ULIRGs or nuclear starbursts, but have star formation which resembles that seen in less-extreme star-forming environments at z ~ 0.

scholarly journals A relationship of polycyclic aromatic hydrocarbon features with galaxy merger in star-forming galaxies at z < 0.2

2017 ◽  
Vol 472 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Katsuhiro L. Murata ◽  
Rika Yamada ◽  
Shinki Oyabu ◽  
Hidehiro Kaneda ◽  
Daisuke Ishihara ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Star Forming ◽  
Polycyclic Aromatic ◽  
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