The Polycyclic Aromatic Hydrocarbon Emission Deficit in Low‐Metallicity Galaxies—A<i>Spitzer</i>View

O’Halloran, B.; Satyapal, S.; Dudik, R. P.

doi:10.1086/500529

Cited by 105 publications

(114 citation statements)

References 53 publications

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“…For the M PAH /M dust , we get ∼2.3 × 10 −4 -much lower than the Galactic value, and consistent with the PAH emission deficit at very low metallicity (Madden 2002;Galliano et al 2003;O'Halloran et al 2006O'Halloran et al , 2008. Correspondingly for the dust to gas ratio, we get ∼1.0 × 10 −2 , using the HI mass from Galametz et al (2009).…”

Section: Morphology Of Ngc 1705supporting

confidence: 81%

Herschelphotometric observations of the low metallicity dwarf galaxy NGC 1705

O’Halloran¹,

Galametz

Madden

et al. 2010

A&A

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We present Herschel SPIRE and PACS photometeric observations of the low metallicity (Z ∼ 0.35 Z ) nearby dwarf galaxy, NGC 1705, in six wavelength bands as part of the Dwarf Galaxy Survey guaranteed time Herschel key program. We confirm the presence of two dominant circumnuclear IR-bright regions surrounding the central super star cluster that had been previously noted at mid-IR wavelengths and in the sub-mm by LABOCA. On constructing a global spectral energy distribution using the SPIRE and PACS photometry, in conjunction with archival IR measurements, we note the presence of an excess at sub-mm wavelengths. This excess suggests the presence of a signiÞcant cold dust component within NGC 1705 and was modeled as an additional cold component in the SED. Although alternative explanations for the sub-mm excess beyond 350 μm, such as changes to the dust emissivity cannot be ruled out, the most likely explanation for the observed submillimetre excess is that of an additional cold dust component.

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Section: Morphology Of Ngc 1705supporting

confidence: 81%

Herschelphotometric observations of the low metallicity dwarf galaxy NGC 1705

O’Halloran¹,

Galametz

Madden

et al. 2010

A&A

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“…We do find a trend with metallicity despite the very narrow metallicity range of our sample, as shown in Figure 11 for the SF subsample. Indeed [Ne ii]12.8 μm has been shown to be the dominant ionization species in H ii region at high metallicity while [Ne iii]15.5 μm takes over in regions of lower density and higher excitation such as low-mass, low-metallicity galaxies (O'Halloran et al 2006;Wu et al 2006 …”

Section: Pah Features Continuum and Emission Linesmentioning

confidence: 99%

Mid-Infrared Spectral Indicators of Star Formation and Active Galactic Nucleus Activity in Normal Galaxies

Treyer¹,

Schiminovich²,

Johnson³

et al. 2010

ApJ

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We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z ∼ 0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey, which includes multiwavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ∼30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [Ne ii]12.8 μm/[O iv]25.9 μm line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs. The luminosity of individual PAH components, of the continuum, and, with poorer statistics, of the neon emission lines and molecular hydrogen lines are found to be tightly correlated to the total infrared (TIR) luminosity, making individual MIR components good gauges of the total dust emission in SF galaxies. Like the TIR luminosity, these individual components can be used to estimate dust attenuation in the UV and in Hα lines based on energy balance arguments. We also propose average scaling relations between these components and dust-corrected, Hα-derived SF rates.

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“…The hardness of the interstellar radiation field may play a major role in the destruction of PAHs in the center of star formation regions (e.g., Madden et al 2006;Bendo et al 2006), and cause the warm infrared colors. The very blue optical color of the YSCC region in ARP 24 (see §3.1) indicates that shocks induced by strong stellar winds and/or supernovae explosions could also be a mechanism for destroying PAHs (O'Halloran et al 2006). Low PAH abundance can also originate from low PAH formation rates due to different dust formation processes in a low metallicity environment (e.g., Hogg et al 2005;Engelbracht et al 2005).…”

Section: Pah and Warm Dust Emissionmentioning

confidence: 99%

Multiwavelength Study of Young Massive Star Clusters in the Interacting Galaxy Arp 24

Cao

2007

Astron J

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We made a multi-wavelength study of young massive star clusters (YSCs) in the interacting galaxy ARP 24, using the optical and ultraviolet images from Hubble Space Telescope (HST), Sloan Digital Sky Survey, and Galaxy Evolution Explorer; the mid-infrared images from Spitzer Space Telescope; and the narrowband Hα image and optical spectra from the NAOC 2.16 m telescope. Based on the HST images, we found that the brightest infrared knot in ARP 24 is associated with a complex of five young massive star clusters, within a region of ∼ 0.95 ′′ radius (127pc) in size. The ages and masses of the star clusters in this complex and other regions were estimated using HST broadband photometries and the Starburst99 synthesis models. The star clusters in this complex are very young (within ages of ∼ 3-5 Myr) and massive (masses of ∼10 5 M ⊙ ). The ionization parameter and metallicity of the complex were estimated using the emission line ratios, and the star formation rates were calculated using monochromatic 24µm, FUV, and Hα line luminosities. We speculate that ARP 24 may formed by a retrograde fly-by encounter indicated by its one-armed appearance and fanlike structure, and the formation of the YSCs in this galaxy is triggered by the interaction. The clusters in the YSC complex may formed in a single giant molecular cloud simultaneously. From the ultraviolet to mid-infrared spectral energy distributions, we found that the region of the YSC complex is relatively bluer in optical and has higher 24µm dust emission relative to the starlight and 8µm emission. This warm infrared color may due to strong UV radiation field or other mechanisms (e.g., shocks) within this region which may destroy the Polycyclic Aromatic Hydrocarbons and enhance the small grain emission at 24µm.

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The Polycyclic Aromatic Hydrocarbon Emission Deficit in Low‐Metallicity Galaxies—ASpitzerView

Cited by 105 publications

References 53 publications

Herschelphotometric observations of the low metallicity dwarf galaxy NGC 1705

Herschelphotometric observations of the low metallicity dwarf galaxy NGC 1705

Mid-Infrared Spectral Indicators of Star Formation and Active Galactic Nucleus Activity in Normal Galaxies

Multiwavelength Study of Young Massive Star Clusters in the Interacting Galaxy Arp 24

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