Thomas Merton Global Prophet

Kramer, Victor A.

doi:10.1111/j.1939-3881.2009.00043_1.x

Cited by 4 publications

(5 citation statements)

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“…Assuming that all the 70‐μm emission comes from big grains, this implies that the dust temperature has an upper limit of 30 K. On the contrary, if we assume that only 60 per cent of the 70‐μm emission is emmited by big grains, the dust temperature decreases to 27 K. The result agrees with the values obtained by Tabatabaei et al (2007) at the location of NGC 595 (see their fig. 1) and is within the range of dust temperatures predicted recently by Kramer et al (2010) for the central part of M33. Another estimate of the dust temperature based on 250–350 μm Herschel emission bands at the location of NGC 595 is T ∼ 25 K (Braine et al 2010).…”

Section: Data Samplingsupporting

confidence: 85%

A photoionization model of the spatial distribution of the optical and mid-infrared properties in NGC 595

Montero

Relaño

Vı́lchez

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We present a set of photoionization models that reproduce simultaneously the observed optical and mid‐infrared spatial distribution of the H ii region NGC 595 in the disc of M33 using the code cloudy. Both optical [Potsdam Multi‐Aperture Spectrophotometer (PMAS) Integral Field Spectroscopy] and mid‐infrared (8‐ and 24‐μm bands from Spitzer) data provide enough spatial resolution to model in a novel approach the inner structure of the H ii region. We define a set of elliptical annular regions around the central ionizing cluster with an uniformity in their observed properties and consider each annulus as an independent thin shell structure. For the first time our models fit the relative surface brightness profiles in both the optical (Hα, [O ii], [O iii]) and the mid‐infrared emissions (8 and 24 μm), under the assumption of a uniform metallicity [12+log(O/H) = 8.45; Esteban et al. 2009] and an age for the stellar cluster of 4.5 Myr (Malumuth et al. 1996). Our models also reproduce the observed uniformity of the R23 parameter and the increase of the [O ii]/[O iii] ratio due to the decrease of the ionization parameter. The variation of the Hα profile is explained in terms of the differences of the occupied volume (the product of filling factor and total volume of the shell) in a matter‐bounded geometry, which also allows us to reproduce the observed pattern of the extinction. The 8 μm/24 μm ratio is low (ranging between 0.04 and 0.4) because it is dominated by the surviving of small dust grains in the H ii region, while the polycyclic aromatic hydrocarbons (PAHs) emit more weakly because they cannot be formed in these thin H ii gas shells. The ratio is also well fitted in our models by assuming a dust‐to‐gas ratio in each annulus compatible with the integrated estimate for the whole H ii region after the 70‐ and 160‐μm Spitzer observations.

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Section: Data Samplingsupporting

confidence: 85%

A photoionization model of the spatial distribution of the optical and mid-infrared properties in NGC 595

Montero

Relaño

Vı́lchez

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…Besides, the large number of star‐forming regions in the disc of M33 allowed us to create a significant statistical sample of objects. Some clear shells have been observed in several wavelength ranges from the optical to the far‐infrared (FIR) with the recent observations from Herschel (Kramer et al 2010; Verley et al 2010). An example is shown in the lower right corner of Fig.…”

Section: Methodssupporting

confidence: 53%

On how leakage can affect the star formation rate estimation using Hα luminosity

Relaño

Kennicutt

Eldridge

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We present observational evidence that leakage of ionizing photons from star‐forming regions can affect the quantification of the star formation rate (SFR) in galaxies. This effect could partially explain the differences between the SFR estimates using the far‐ultraviolet (FUV) and the Hα emission. We find that leakage could decrease the SFR(Hα)/SFR(FUV) ratio by up to 25 per cent. The evidence is based on the observation that the SFR(Hα)/SFR(FUV) ratio is lower for objects showing a shell Hα structure than for regions exhibiting a much more compact morphology. The study has been performed on three object samples: low‐luminosity dwarf galaxies from the Local Volume Legacy survey, star‐forming regions in the Large Magellanic Cloud and the nearby Local Group galaxy M33. For the three samples we find differences (1.1σ–1.4σ) between the SFR(Hα)/SFR(FUV) for compact and shell objects. Although leakage cannot entirely explain the observed trend of SFR(Hα)/SFR(FUV) ratios for systems with low SFR, we show that the mechanism can lead to different SFR estimates when using Hα and FUV luminosities. Therefore, further study is needed to constrain the contribution of leakage to the low SFR(Hα)/SFR(FUV) ratios observed in dwarf galaxies and its impact on the Hα flux as an SFR indicator in such objects.

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“…star‐forming regions) will be warm enough to emit at m but this small fraction of dust (by mass) can strongly influence the temperature of the isothermal fits. The bulk of the ISM (and therefore the dust) resides in the diffuse phase which is heated by the interstellar radiation field to a cooler temperature typically in the range of 15–20 K (Helou 1986; DE01 and references within; Popescu et al 2002; VDE05; Draine et al 2007; Willmer et al 2009; Bendo et al 2010; Bernard et al 2010; Boselli et al 2010; Kramer et al 2010; Planck Collaboration 2011b). For more accurate dust mass estimates we require the mass‐weighted temperature of the dust emitting at 250 m which requires fitting a model with multiple (at least two) temperature components.…”

Section: Dust Mass and Luminositymentioning

confidence: 99%

Herschel★-ATLAS: rapid evolution of dust in galaxies over the last 5 billion years

Dunne¹,

Gomez²,

Cunha³

et al. 2011

Monthly Notices of the Royal Astronomical Society

231

296

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We present the first direct and unbiased measurement of the evolution of the dust mass function of galaxies over the past 5 billion years of cosmic history using data from the Science Demonstration Phase of the Herschel‐Astrophysical Terahertz Large Area Survey (Herschel‐ATLAS). The sample consists of galaxies selected at 250 m which have reliable counterparts from the Sloan Digital Sky Survey (SDSS) at z < 0.5, and contains 1867 sources. Dust masses are calculated using both a single‐temperature grey‐body model for the spectral energy distribution and also a model with multiple temperature components. The dust temperature for either model shows no trend with redshift. Splitting the sample into bins of redshift reveals a strong evolution in the dust properties of the most massive galaxies. At z= 0.4–0.5, massive galaxies had dust masses about five times larger than in the local Universe. At the same time, the dust‐to‐stellar mass ratio was about three to four times larger, and the optical depth derived from fitting the UV‐sub‐mm data with an energy balance model was also higher. This increase in the dust content of massive galaxies at high redshift is difficult to explain using standard dust evolution models and requires a rapid gas consumption time‐scale together with either a more top‐heavy initial mass function (IMF), efficient mantle growth, less dust destruction or combinations of all three. This evolution in dust mass is likely to be associated with a change in overall interstellar medium mass, and points to an enhanced supply of fuel for star formation at earlier cosmic epochs.

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Thomas Merton Global Prophet

Cited by 4 publications

References 0 publications

A photoionization model of the spatial distribution of the optical and mid-infrared properties in NGC 595

A photoionization model of the spatial distribution of the optical and mid-infrared properties in NGC 595

On how leakage can affect the star formation rate estimation using Hα luminosity

Herschel★-ATLAS: rapid evolution of dust in galaxies over the last 5 billion years

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