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Author

Frank P. Israel

Other affiliations: Max Planck Society
Bio: Frank P. Israel is an academic researcher from Leiden University. The author has contributed to research in topics: Galaxy & Star formation. The author has an hindex of 63, co-authored 266 publications receiving 12198 citations. Previous affiliations of Frank P. Israel include Max Planck Society.


Papers
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Journal ArticleDOI
Timothy W. Shimwell1, Huub Röttgering1, Philip Best2, Wendy L. Williams3, T. J. Dijkema4, F. de Gasperin1, Martin J. Hardcastle3, George Heald5, D. N. Hoang1, A. Horneffer6, Huib Intema1, Elizabeth K. Mahony4, Elizabeth K. Mahony7, Subhash C. Mandal1, A. P. Mechev1, Leah K. Morabito1, J. B. R. Oonk4, J. B. R. Oonk1, D. A. Rafferty8, E. Retana-Montenegro1, J. Sabater2, Cyril Tasse9, Cyril Tasse10, R. J. van Weeren11, Marcus Brüggen8, Gianfranco Brunetti12, Krzysztof T. Chyzy13, John Conway14, Marijke Haverkorn15, Neal Jackson16, Matt J. Jarvis17, Matt J. Jarvis18, John McKean4, George K. Miley1, Raffaella Morganti4, Raffaella Morganti19, Glenn J. White20, Glenn J. White21, Michael W. Wise4, Michael W. Wise22, I. van Bemmel23, Rainer Beck6, Marisa Brienza4, Annalisa Bonafede8, G. Calistro Rivera1, Rossella Cassano12, A. O. Clarke16, D. Cseh15, Adam Deller4, A. Drabent, W. van Driel24, W. van Driel9, D. Engels8, Heino Falcke15, Heino Falcke4, Chiara Ferrari25, S. Fröhlich26, M. A. Garrett4, Jeremy J. Harwood4, Volker Heesen27, Matthias Hoeft23, Cathy Horellou14, Frank P. Israel1, Anna D. Kapińska28, Anna D. Kapińska29, Magdalena Kunert-Bajraszewska, D. J. McKay30, D. J. McKay20, N. R. Mohan31, Emanuela Orru4, R. Pizzo4, R. Pizzo19, Isabella Prandoni12, Dominik J. Schwarz32, Aleksandar Shulevski4, M. Sipior4, Daniel J. Smith3, S. S. Sridhar4, S. S. Sridhar19, Matthias Steinmetz33, Andra Stroe34, Eskil Varenius14, P. van der Werf1, J. A. Zensus6, Jonathan T. L. Zwart35, Jonathan T. L. Zwart17 
TL;DR: The LOFAR Two-metre Sky Survey (LoTSS) as mentioned in this paper is a deep 120-168 MHz imaging survey that will eventually cover the entire northern sky, where each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ~5? resolution images with a sensitivity of ~100?Jy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure.
Abstract: The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ~5? resolution images with a sensitivity of ~100 ?Jy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Owing to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. In this paper we provide an overview of the LoTSS. We outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-Area low-frequency survey. In excess of 44 000 sources are detected in the images that have a resolution of 25?, typical noise levels of less than 0.5 mJy/beam, and cover an area of over 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45°00?00? to 57°00?00?).

447 citations

Journal ArticleDOI
TL;DR: In this article, a grid of XDR and PDR models that span ranges in density (10 2 10 6.5 cm 3 ), irradiation (10 0.5 10 5 G0 and FX = 1.6 × 10 2 160 erg cm 2 s 1 ) and column density (3 × 10 21 1 × 10 25 cm 2 ).
Abstract: Aims. The nuclei of active galaxies harbor massive young stars, an accreting central black hole, or both. In order to determine the physical conditions that pertain to molecular gas close to t he sources of radiation, numerical models are constructed. Methods. These models iteratively determine the thermal and chemical balance of molecular gas that is exposed to X-rays (1-100 keV) and far-ultraviolet radiation (6-13.6 eV), as a functi on of depth. Results. We present a grid of XDR and PDR models that span ranges in density (10 2 10 6.5 cm 3 ), irradiation (10 0.5 10 5 G0 and FX = 1.6 × 10 2 160 erg cm 2 s 1 ) and column density (3 × 10 21 1 × 10 25 cm 2 ). Predictions are made for the most important atomic fine-structure lines, e.g., [CII], [OI], [ CI], [SiII], and for molecular species like HCO + , HCN, HNC, CS and SiO up to J = 4, CO and 13 CO up to J = 16, and column densities for CN, CH, CH + , HCO, HOC + , NO and N2H + . We find that surface temperatures are higher (lower) in PDRs compared to XDRs for densities > 10 4 ( 1) for XDRs (PDRs) if the density exceeds 10 5 cm 3 and if the column density is larger than 10 23 cm 2 . For columns less than 10 22.5 cm 2 the XDR HCN/HCO + 1-0 ratio becomes larger than one, although the individual HCN 1-0 and HCO + 1-0 line intensities are weaker. For modest densities, n = 10 4 10 5 cm 3 , and strong radiation fields ( > 100 erg s 1 cm 2 ), HCN/HCO + ratios can become larger in XDRs than PDRs as well. Also, the HCN/CO 1-0 ratio is typically smaller in XDRs, and the HCN emission in XDRs is boosted with respect to CO only for high (column) density gas, with columns in excess of 10 23 cm 2 and densities larger than 10 4 cm 3 . Furthermore, CO is typically warmer in XDRs than in PDRs, for the same total energy input. This leads to higher CO J=N+1-N/CO 1-0, N � 1, line ratios in XDRs. In particular, lines with N � 10, like CO(16-15) and CO(10-9) observable with HIFI/Herschel, discriminate very well between XDRs and PDRs. This is crucial since the XDR/AGN contribution will typically be of a much smaller (possibly beam diluted) angular scale and a 10-25% PDR contribution can already suppress XDR distinguishing features involving HCN/HCO+ and HNC/HCN. For possible future observations, column density ratios indicate that CH, CH + , NO, HOC + and HCO

426 citations

Journal ArticleDOI
TL;DR: In this article, a full high-resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231 is presented, including 25 lines, including CO J = 5-4 through J = 13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H 2O+, CH+, and HF.
Abstract: We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231. In total 25 lines are detected, including CO J = 5-4 through J = 13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels up to J = 8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J = 8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk 231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk 231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J = 8. X-rays from the accreting supermassive black hole in Mrk 231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk 231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.

343 citations

Journal ArticleDOI
TL;DR: In this paper, a full high-resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk231 is presented, including 25 lines, including CO J=5-4 through J=13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H 2O+, CH+, and HF.
Abstract: We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk231. In total 25 lines are detected, including CO J=5-4 through J=13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels up to J=8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J=8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J=8. X-rays from the accreting supermassive black hole in Mrk231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.

308 citations

Journal ArticleDOI
TL;DR: In this paper, the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the Tidally stripped, low metallicity Small Magellanic Cloud) Spitzer Legacy program was used to study the amount and type of dust in the present interstellar medium.
Abstract: The Small Magellanic Cloud (SMC) provides a unique laboratory for the study of the lifecycle of dust given its low metallicity (~1/5 solar) and relative proximity (~60 kpc). This motivated the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity Small Magellanic Cloud) Spitzer Legacy program with the specific goals of studying the amount and type of dust in the present interstellar medium, the sources of dust in the winds of evolved stars, and how much dust is consumed in star formation. This program mapped the full SMC (30 deg^2) including the body, wing, and tail in seven bands from 3.6 to 160 μm using IRAC and MIPS on the Spitzer Space Telescope. The data were reduced and mosaicked, and the point sources were measured using customized routines specific for large surveys. We have made the resulting mosaics and point-source catalogs available to the community. The infrared colors of the SMC are compared to those of other nearby galaxies and the 8 μm/24 μm ratio is somewhat lower than the average and the 70 μm/160 μm ratio is somewhat higher than the average. The global infrared spectral energy distribution (SED) shows that the SMC has approximately 1/3 the aromatic emission/polycyclic aromatic hydrocarbon abundance of most nearby galaxies. Infrared color-magnitude diagrams are given illustrating the distribution of different asymptotic giant branch stars and the locations of young stellar objects. Finally, the average SED of H II/star formation regions is compared to the equivalent Large Magellanic Cloud average H II/star formation region SED. These preliminary results will be expanded in detail in subsequent papers.

255 citations


Cited by
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TL;DR: In this paper, the authors review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies.
Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

2,525 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the theoretical underpinning, techniques, and results of efforts to estimate the CO-to-H2 conversion factor in different environments, and recommend a conversion factor XCO = 2×10 20 cm −2 (K km s −1 ) −1 with ±30% uncertainty.
Abstract: CO line emission represents the most accessible and widely used tracer of the molecular interstellar medium. This renders the translation of observed CO intensity into total H2 gas mass critical to understand star formation and the interstellar medium in our Galaxy and beyond. We review the theoretical underpinning, techniques, and results of efforts to estimate this CO-to-H2 “conversion factor,” XCO, in different environments. In the Milky Way disk, we recommend a conversion factor XCO = 2×10 20 cm −2 (K km s −1 ) −1 with ±30% uncertainty. Studies of other “normal galaxies” return similar values in Milky Way-like disks, but with greater scatter and systematic uncertainty. Departures from this Galactic conversion factor are both observed and expected. Dust-based determinations, theoretical arguments, and scaling relations all suggest that XCO increases with decreasing metallicity, turning up sharply below metallicity ≈ 1/3–1/2 solar in a manner consistent with model predictions that identify shielding as a key parameter. Based on spectral line modeling and dust observations, XCO appears to drop in the central, bright regions of some but not all galaxies, often coincident with regions of bright CO emission and high stellar surface density. This lower XCO is also present in the overwhelmingly molecular interstellar medium of starburst galaxies, where several lines of evidence point to a lower CO-to-H2 conversion factor. At high redshift, direct evidence regarding the conversion factor remains scarce; we review what is known based on dynamical modeling and other arguments. Subject headings: ISM: general — ISM: molecules — galaxies: ISM — radio lines: ISM

2,004 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a comprehensive analysis of the relationship between star formation rate surface density and gas surface density at sub-kpc resolution in a sample of 18 nearby galaxies and investigate how the star formation law differs between the H2 dominated centers of spiral galaxies, their H I dominated outskirts and the H I rich late-type/dwarf galaxies.
Abstract: We present a comprehensive analysis of the relationship between star formation rate surface density, ΣSFR, and gas surface density, Σgas, at sub-kpc resolution in a sample of 18 nearby galaxies. We use high-resolution H I data from The H I Nearby Galaxy Survey, CO data from HERACLES and the BIMA Survey of Nearby Galaxies, 24 μm data from the Spitzer Space Telescope, and UV data from the Galaxy Evolution Explorer. We target seven spiral galaxies and 11 late-type/dwarf galaxies and investigate how the star formation law differs between the H2 dominated centers of spiral galaxies, their H I dominated outskirts and the H I rich late-type/dwarf galaxies. We find that a Schmidt-type power law with index N = 1.0 ± 0.2 relates ΣSFR and ΣH2 across our sample of spiral galaxies, i.e., that H2 forms stars at a constant efficiency in spirals. The average molecular gas depletion time is ~2 × 109 years. The range of ΣH2 over which we measure this relation is ~3-50 M ☉ pc–2, significantly lower than in starburst environments. We find the same results when performing a pixel-by-pixel analysis, averaging in radial bins, or when varying the star formation tracer used. We interpret the linear relation and constant depletion time as evidence that stars are forming in giant molecular clouds with approximately uniform properties and that ΣH2 may be more a measure of the filling fraction of giant molecular clouds than changing conditions in the molecular gas. The relationship between total gas surface density (Σgas) and ΣSFR varies dramatically among and within spiral galaxies. Most galaxies show little or no correlation between ΣHI and ΣSFR. As a result, the star formation efficiency (SFE), ΣSFR/Σgas, varies strongly across our sample and within individual galaxies. We show that this variation is systematic and consistent with the SFE being set by local environmental factors: in spirals the SFE is a clear function of radius, while the dwarf galaxies in our sample display SFEs similar to those found in the outer optical disks of the spirals. We attribute the similarity to common environments (low density, low metallicity, H I dominated) and argue that shear (which is typically absent in dwarfs) cannot drive the SFE. In addition to a molecular Schmidt law, the other general feature of our sample is a sharp saturation of H I surface densities at ΣHI ≈ 9 M ☉ pc–2 in both the spiral and dwarf galaxies. In the case of the spirals, we observe gas in excess of this limit to be molecular.

1,842 citations

Journal ArticleDOI
TL;DR: In this article, a large set of theoretical isochrones are presented, whose distinctive features mostly reside on the greatly improved treatment of the thermally-pulsing asymptotic giant branch (TP-AGB) phase.
Abstract: We present a large set of theoretical isochrones, whose distinctive features mostly reside on the greatly-improved treatment of the thermally-pulsing asymptotic giant branch (TP-AGB) phase. Essentially, we have coupled the TP-AGB tracks described in Paper I, at their stages of pre-flash quiescent H-shell burning, with the evolutionary tracks for the previous evolutionary phases from Girardi et al. (2000, AA the bell-shaped sequences in the Hertzsprung-Russell (HR) diagram for stars with hot-bottom burning; the changes of pulsation mode between fundamental and first overtone; the sudden changes of mean mass-loss rates as the surface chemistry changes from M- to C-type; etc. Theoretical isochrones are then converted to about 20 different photometric systems - including traditional ground-based systems, and those of recent major wide-field surveys such as SDSS, OGLE, DENIS, 2MASS, UKIDSS, etc., - by means of synthetic photometry applied to an updated library of stellar spectra, suitably extended to include C-type stars. Finally, we correct the predicted photometry for the effect of circumstellar dust during the mass-losing stages of the AGB evolution, which allows us to improve the results for the optical-to-infrared systems, and to simulate mid- and far-IR systems such as those of Spitzer and AKARI. We illustrate the most striking properties of these isochrones by means of basic comparisons with observational data for the Milky Way disc and the Magellanic Clouds. Access to the data is provided both via a web repository of static tables (http://stev.oapd.inaf.it/ dustyAGB07 and CDS), and via an interactive web interface (http://stev.oapd. inaf. it/cmd), which provides tables for any intermediate value of age and metallicity, for several photometric systems, and for different choices of dust properties.

1,740 citations

Journal ArticleDOI
TL;DR: The Modules for Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST) project as discussed by the authors provides a set of stellar evolutionary tracks and isochrones computed using MESA, a state-of-the-art 1D stellar evolution package.
Abstract: This is the first of a series of papers presenting the Modules for Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST) project, a new comprehensive set of stellar evolutionary tracks and isochrones computed using MESA, a state-of-the-art open-source 1D stellar evolution package. In this work, we present models with solar-scaled abundance ratios covering a wide range of ages ($5 \leq \rm \log(Age)\;[yr] \leq 10.3$), masses ($0.1 \leq M/M_{\odot} \leq 300$), and metallicities ($-2.0 \leq \rm [Z/H] \leq 0.5$). The models are self-consistently and continuously evolved from the pre-main sequence to the end of hydrogen burning, the white dwarf cooling sequence, or the end of carbon burning, depending on the initial mass. We also provide a grid of models evolved from the pre-main sequence to the end of core helium burning for $-4.0 \leq \rm [Z/H] < -2.0$. We showcase extensive comparisons with observational constraints as well as with some of the most widely used existing models in the literature. The evolutionary tracks and isochrones can be downloaded from the project website at this http URL

1,301 citations