We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space O... more We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3–500 μm spectral energy distributions (SEDs) of galaxies at 0< z< 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes.
Context. Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often u... more Context. Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often used to deduce the total molecular hydrogen but is challenging to detect in low-metallicity galaxies in spite of the star formation taking place. In contrast, the [C II]λ158 μm is relatively bright, highlighting a potentially important reservoir of H2 that is not traced by CO (1−0) but is residing in the C+-emitting regions. Aims. Here we aim to explore a method to quantify the total H2 mass (MH2) in galaxies and to decipher what parameters control the CO-dark reservoir. Methods. We present Cloudy grids of density, radiation field, and metallicity in terms of observed quantities, such as [O I], [C I], CO (1−0), [C II], LTIR, and the total MH2. We provide recipes based on these models to derive total MH2 mass estimates from observations. We apply the models to the Herschel Dwarf Galaxy Survey, extracting the total MH2 for each galaxy, and compare this to the H2 determined from the observed...
We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the envi... more We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the environment has had on galaxies. We consider Virgo cluster and field samples and also assign a density contrast parameter to each galaxy, as defined by the local density of SDSS galaxies. We consider their chemical evolution (using MDust/MBaryon and MGas/MBaryon), their specific star formation rate (SFR/MStars), star formation efficiency (SFR/MGas), stars-to-dust mass ratio (MStars/MDust), gas-to-dust mass ratio (MGas/MDust) and the relationship between star formation rate per unit mass of dust and dust temperature (SFR/MDust and TDust). Late type galaxies (later than Sc) in all of the environments can be modelled using simple closed box chemical evolution and a simple star formation history (SFR(t) ∝ t exp−t/τ). For earlier type galaxies the physical mechanisms that give rise to their properties are clearly much more varied and require a more complicated model (mergers, gas in or outflow). ...
Aims. We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies o... more Aims. We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies of different morphological types. The targets constitute the vast majority (93%) of the DustPedia sample, including almost all large (optical diameter larger than 1′), nearby (v ≤ 3000 km s−1) galaxies observed with the Herschel Space Observatory. Methods. For each object, we modelled the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the Code Investigating GALaxy Evolution (CIGALE). The value of fabs was obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit. Results. On average, 19% of the stellar radiation is absorbed by dust in DustPedia galaxies. The fraction rises to 25% if only late-type galaxies are considered. The dependence of fabs on morphology, showing a peak for Sb-Sc galaxies, is weak; it reflects a stronger, yet broad, positi...
Recent Spitzer and ISO observations (Engelbracht et al. 2005, ApJ, 628, L29; Madden et al. 2005, ... more Recent Spitzer and ISO observations (Engelbracht et al. 2005, ApJ, 628, L29; Madden et al. 2005, A&A, astro-ph/0510086) have confirmed the correlation between the metallicity, Z, of a galaxy's ISM and the relative intensity of the thermal emission by its Polycyclic Aromatic Hydrocarbons (PAHs). One explanation that has been proposed to this phenomenon is that the low dust content of
ABSTRACT More complete knowledge of galaxy evolution requires understanding the process of star f... more ABSTRACT More complete knowledge of galaxy evolution requires understanding the process of star formation and interaction between the interstellar radiation field and the ISM in galactic environments traversing a wide range of physical parameter space. Here we focus on the impact of star formation on the surrounding low metallicity ISM. Indeed, lowering the metal abundance, as is the case of some galaxies of the early universe, results in an overall lower galactic dust reservoir, hence, less shielding for the formation of the molecular gas necessary for star formation to proceed. A convenient laboratory to zoom into the various phases of the ISM to study the effects of low metallicity on the ISM properties, is our nearest neighbor, the Large Magellanic Cloud, which has a metallicity 1/2 that of solar. The goal is to construct a comprehensive, self-consistent picture of the density, radiation field, and ISM structure in the vicinity of one of the most massive star clusters in our local neighborhood, R136.
The Herschel Dwarf Galaxy Survey investigates the metal enrichment of the dust and gas in galaxie... more The Herschel Dwarf Galaxy Survey investigates the metal enrichment of the dust and gas in galaxies through observations of the local universe dwarf galaxies via the new far-infrared (FIR) and submillimetre imaging spectroscopic and photometric observations from the recently launched Herschel Space Observatory. The dust spectral energy distributions can now be constrained out to submm wavelengths and often show a
The feedback between massive stars and the interstellar medium dominates the evolution of their h... more The feedback between massive stars and the interstellar medium dominates the evolution of their host galaxies. Therefore, to understand galaxy evolution, we must understand how massive star clusters process local gas and dust (radiatively and mechanically), and how strong stellar winds interact with the HII region. Super-star clusters are the sites of the most energetic star formation in the universe,
The Herschel Reference Survey is a Herschel guaranteed time key project and will be a benchmark s... more The Herschel Reference Survey is a Herschel guaranteed time key project and will be a benchmark study of dust in the nearby universe. The survey will complement a number of other Herschel key projects including large cosmological surveys that trace dust in the distant universe. We will use Herschel to produce images of a statistically-complete sample of 323 galaxies at 250, 350, and 500um. The sample is volume-limited, containing sources with distances between 15 and 25Mpc and flux limits in the K band to minimize the ...
Proceedings of The International Astronomical Union, 2011
We present the 450-1550 GHz spectra of three nearby Seyfert galaxies (NGC1068, NGC7130 and NGC758... more We present the 450-1550 GHz spectra of three nearby Seyfert galaxies (NGC1068, NGC7130 and NGC7582) taken with the Herschel SPIRE FTS. For the case of NGC1068 we reconstruct the nuclear spectral line energy distribution (SLED) of the CO lines, applying nonLTE radiative transfer and a Bayesian likelihood analysis to estimate the physical properties of the molecular gas in the circumnuclear
We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space O... more We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3–500 μm spectral energy distributions (SEDs) of galaxies at 0< z< 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes.
Context. Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often u... more Context. Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often used to deduce the total molecular hydrogen but is challenging to detect in low-metallicity galaxies in spite of the star formation taking place. In contrast, the [C II]λ158 μm is relatively bright, highlighting a potentially important reservoir of H2 that is not traced by CO (1−0) but is residing in the C+-emitting regions. Aims. Here we aim to explore a method to quantify the total H2 mass (MH2) in galaxies and to decipher what parameters control the CO-dark reservoir. Methods. We present Cloudy grids of density, radiation field, and metallicity in terms of observed quantities, such as [O I], [C I], CO (1−0), [C II], LTIR, and the total MH2. We provide recipes based on these models to derive total MH2 mass estimates from observations. We apply the models to the Herschel Dwarf Galaxy Survey, extracting the total MH2 for each galaxy, and compare this to the H2 determined from the observed...
We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the envi... more We use a sub-set of the DustPedia galaxy sample (461 galaxies) to investigate the effect the environment has had on galaxies. We consider Virgo cluster and field samples and also assign a density contrast parameter to each galaxy, as defined by the local density of SDSS galaxies. We consider their chemical evolution (using MDust/MBaryon and MGas/MBaryon), their specific star formation rate (SFR/MStars), star formation efficiency (SFR/MGas), stars-to-dust mass ratio (MStars/MDust), gas-to-dust mass ratio (MGas/MDust) and the relationship between star formation rate per unit mass of dust and dust temperature (SFR/MDust and TDust). Late type galaxies (later than Sc) in all of the environments can be modelled using simple closed box chemical evolution and a simple star formation history (SFR(t) ∝ t exp−t/τ). For earlier type galaxies the physical mechanisms that give rise to their properties are clearly much more varied and require a more complicated model (mergers, gas in or outflow). ...
Aims. We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies o... more Aims. We aim to study the fraction of stellar radiation absorbed by dust, fabs, in 814 galaxies of different morphological types. The targets constitute the vast majority (93%) of the DustPedia sample, including almost all large (optical diameter larger than 1′), nearby (v ≤ 3000 km s−1) galaxies observed with the Herschel Space Observatory. Methods. For each object, we modelled the spectral energy distribution from the ultraviolet to the sub-millimetre using the dedicated, aperture-matched DustPedia photometry and the Code Investigating GALaxy Evolution (CIGALE). The value of fabs was obtained from the total luminosity emitted by dust and from the bolometric luminosity, which are estimated by the fit. Results. On average, 19% of the stellar radiation is absorbed by dust in DustPedia galaxies. The fraction rises to 25% if only late-type galaxies are considered. The dependence of fabs on morphology, showing a peak for Sb-Sc galaxies, is weak; it reflects a stronger, yet broad, positi...
Recent Spitzer and ISO observations (Engelbracht et al. 2005, ApJ, 628, L29; Madden et al. 2005, ... more Recent Spitzer and ISO observations (Engelbracht et al. 2005, ApJ, 628, L29; Madden et al. 2005, A&A, astro-ph/0510086) have confirmed the correlation between the metallicity, Z, of a galaxy's ISM and the relative intensity of the thermal emission by its Polycyclic Aromatic Hydrocarbons (PAHs). One explanation that has been proposed to this phenomenon is that the low dust content of
ABSTRACT More complete knowledge of galaxy evolution requires understanding the process of star f... more ABSTRACT More complete knowledge of galaxy evolution requires understanding the process of star formation and interaction between the interstellar radiation field and the ISM in galactic environments traversing a wide range of physical parameter space. Here we focus on the impact of star formation on the surrounding low metallicity ISM. Indeed, lowering the metal abundance, as is the case of some galaxies of the early universe, results in an overall lower galactic dust reservoir, hence, less shielding for the formation of the molecular gas necessary for star formation to proceed. A convenient laboratory to zoom into the various phases of the ISM to study the effects of low metallicity on the ISM properties, is our nearest neighbor, the Large Magellanic Cloud, which has a metallicity 1/2 that of solar. The goal is to construct a comprehensive, self-consistent picture of the density, radiation field, and ISM structure in the vicinity of one of the most massive star clusters in our local neighborhood, R136.
The Herschel Dwarf Galaxy Survey investigates the metal enrichment of the dust and gas in galaxie... more The Herschel Dwarf Galaxy Survey investigates the metal enrichment of the dust and gas in galaxies through observations of the local universe dwarf galaxies via the new far-infrared (FIR) and submillimetre imaging spectroscopic and photometric observations from the recently launched Herschel Space Observatory. The dust spectral energy distributions can now be constrained out to submm wavelengths and often show a
The feedback between massive stars and the interstellar medium dominates the evolution of their h... more The feedback between massive stars and the interstellar medium dominates the evolution of their host galaxies. Therefore, to understand galaxy evolution, we must understand how massive star clusters process local gas and dust (radiatively and mechanically), and how strong stellar winds interact with the HII region. Super-star clusters are the sites of the most energetic star formation in the universe,
The Herschel Reference Survey is a Herschel guaranteed time key project and will be a benchmark s... more The Herschel Reference Survey is a Herschel guaranteed time key project and will be a benchmark study of dust in the nearby universe. The survey will complement a number of other Herschel key projects including large cosmological surveys that trace dust in the distant universe. We will use Herschel to produce images of a statistically-complete sample of 323 galaxies at 250, 350, and 500um. The sample is volume-limited, containing sources with distances between 15 and 25Mpc and flux limits in the K band to minimize the ...
Proceedings of The International Astronomical Union, 2011
We present the 450-1550 GHz spectra of three nearby Seyfert galaxies (NGC1068, NGC7130 and NGC758... more We present the 450-1550 GHz spectra of three nearby Seyfert galaxies (NGC1068, NGC7130 and NGC7582) taken with the Herschel SPIRE FTS. For the case of NGC1068 we reconstruct the nuclear spectral line energy distribution (SLED) of the CO lines, applying nonLTE radiative transfer and a Bayesian likelihood analysis to estimate the physical properties of the molecular gas in the circumnuclear
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Papers by F. Galliano