@misc{madau2017cosmic, abstract = {The reionization of cosmic hydrogen marks a critical juncture in the history of structure formation in the universe. Here we present a new formulation of the standard reionization equation for the evolution of the volume-averaged HII fraction that is more consistent with the accepted conceptual model of inhomogeneous intergalactic absorption. The revised equation retains the basic terminology and simplicity of the classic calculation but explicitly accounts for the presence of the optically thick "Lyman-limit systems" that are known to determine the mean free path of ionizing radiation after overlap. Integration of this equation provides a better characterization of the timing of reionization by smoothly linking the pre-overlap with the post-overlap phases of such process. We confirm the validity of the quasi-instantaneous approximation as predictor of reionization completion/maintenance, and discuss new insights on the sources of cosmic reionization using the improved formalism. A constant emission rate into the intergalactic medium (IGM) of 3 Lyman continuum (LyC) photons per atom per Gyr leads to a reionization history that is consistent with a number of observational constraints on the ionization state of the z=5-9 universe and with the reduced Thomson scattering optical depth recently reported by the Planck Collaboration. While star-forming galaxies can dominate the reionization process if the luminosity-weighted fraction of LyC photons that escape into the IGM, f_esc, exceeds 15% (for a faint magnitude cut-off of the galaxy UV luminosity function of M_lim=-13 and a LyC photon yield per unit 1500 AA luminosity of xi_ion=10^{25.3} Hz/erg, simple models where the product of the two unknowns f_esc xi_ion is not evolving with redshift fail to reproduce the changing neutrality of the IGM observed at these epochs.}, added-at = {2017-10-24T10:12:16.000+0200}, author = {Madau, Piero}, biburl = {https://www.bibsonomy.org/bibtex/2dcbd4cb0371a34b68e7bc9bcefc16c25/miki}, description = {[1710.07636] Cosmic Reionization After Planck and Before JWST: An Analytic Approach}, interhash = {3a77a703c9637a095c381d2dc4b7e7fe}, intrahash = {dcbd4cb0371a34b68e7bc9bcefc16c25}, keywords = {HII analytic approach escape evolution region reionization}, note = {cite arxiv:1710.07636Comment: 11 pages, 3 figures, submitted to the Astrophysical Journal}, timestamp = {2017-10-24T10:12:16.000+0200}, title = {Cosmic Reionization After Planck and Before JWST: An Analytic Approach}, url = {http://arxiv.org/abs/1710.07636}, year = 2017 } @misc{sanders2017biases, abstract = {Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of HII and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for HII regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally-motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the HII region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single HII regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.}, added-at = {2017-08-17T10:07:26.000+0200}, author = {Sanders, Ryan L. and Shapley, Alice E. and Zhang, Kai and Yan, Renbin}, biburl = {https://www.bibsonomy.org/bibtex/2ab7d49bdc1e0bf81250bfb860f8c9367/miki}, description = {[1708.04625] Biases in metallicity measurements from global galaxy spectra: the effects of flux-weighting and diffuse ionized gas contamination}, interhash = {6c0d28ab416d5951b07b55c0d55f13ef}, intrahash = {ab7d49bdc1e0bf81250bfb860f8c9367}, keywords = {DIG HII combined models regions}, note = {cite arxiv:1708.04625Comment: 35 pages, 27 figures, 4 tables. Submitted to ApJ. See Figures 15-17 for typical global galaxy biases in strong-line ratios, electron temperatures, and direct-method metallicities}, timestamp = {2017-08-17T10:07:26.000+0200}, title = {Biases in metallicity measurements from global galaxy spectra: the effects of flux-weighting and diffuse ionized gas contamination}, url = {http://arxiv.org/abs/1708.04625}, year = 2017 } @misc{chardin2017seven, abstract = {High-signal to noise observations of the Ly$\alpha$ forest transmissivity in the z = 7.085 QSO ULAS J1120+0641 show seven narrow transmission spikes followed by a long 240 cMpc/h trough. Here we use radiative transfer simulations of cosmic reionization previously calibrated to match a wider range of Ly$\alpha$ forest data to show that the occurrence of seven transmission spikes in the narrow redshift range z = 5.85 - 6.1 is very sensitive to the exact timing of reionization. Occurrence of the spikes requires the most under dense regions of the IGM to be already fully ionised. The rapid onset of a long trough at z = 6.12 requires a strong decrease of the photo-ionisation rate at z$\sim$6.1 in this line-of-sight, consistent with the end of percolation at this redshift. The narrow range of reionisation histories that we previously found to be consistent with a wider range of Ly$\alpha$ forest data have a reasonable probability of showing seven spikes and the mock absorption spectra provide an excellent match to the spikes and the trough in the observed spectrum of ULAS J1120+0641. Despite the large overall opacity of Ly$\alpha$ at z > 5.8, larger samples of high signal-to-noise observations of rare transmission spikes should therefore provide important further insights into the exact timing of the percolation of HII bubbles at the tail-end of reionization}, added-at = {2017-07-14T09:38:42.000+0200}, author = {Chardin, Jonathan and haehnelt, Martin G. and Bosman, Sarah E. I. and Puchwein, Ewald}, biburl = {https://www.bibsonomy.org/bibtex/2f3b29e5139e3957ceeeb48ec889c289c/miki}, description = {[1707.03841] A tale of seven narrow spikes and a long trough: constraining the timing of the percolation of HII bubbles at the tail-end of reionization with ULAS J1120+0641}, interhash = {36e11054740cef4d24922b8f651335f1}, intrahash = {f3b29e5139e3957ceeeb48ec889c289c}, keywords = {HII bubbles percolation reionization}, note = {cite arxiv:1707.03841Comment: 11 pages, 11 figures, submitted to MNRAS}, timestamp = {2017-07-14T09:38:42.000+0200}, title = {A tale of seven narrow spikes and a long trough: constraining the timing of the percolation of HII bubbles at the tail-end of reionization with ULAS J1120+0641}, url = {http://arxiv.org/abs/1707.03841}, year = 2017 } @misc{palmeirim2017spatial, abstract = {We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1 360 bubble structures throughout the Galactic Plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved star-forming objects are found spatially located near the center, while younger star-forming objects are found at the edge of the bubbles. We derived dynamic ages for a subsample of 182 Hii regions for which kinematic distances and radio continuum flux measurements were available. We detect ~80% more star-forming sources per unit area in the direction of bubbles than in the surrounding fields. We estimate ~10% clump formation efficiency (CFE) of Hi-GAL clumps in bubbles, twice the CFE in fields not affected by feedback. We find higher CFE of protostellar clumps in younger bubbles, whose density of the bubble shells is higher. We argue that the formation rate from prestellar to protostellar phase is probably higher during the early stages of the bubble expansion. Evaluation of the fragmentation time inside the shell of bubbles advocates the preexistence of clumps in the medium before the bubble, as supported by numerical simulations. Approximately 23% of the Hi-GAL clumps are found located in the direction of a bubble, with 15% for prestellar clumps and 41% for protostellar clumps. We argue that the high fraction of protostellar clumps may be due to the acceleration of the star-formation process cause by the feedback of the (Hii) bubbles.}, added-at = {2017-05-30T09:52:56.000+0200}, author = {Palmeirim, P. and Zavagno, A. and Elia, D. and Moore, T. J. T. and Whitworth, A. and Tremblin, P. and Traficante, A. and Merello, M. and Russeil, D. and Pezzuto, S. and Cambrésy, L. and Baldeschi, A. and Bandieramonte, M. and Becciani, U. and Benedettini, M. and Buemi, C. and Bufano, F. and Bulpitt, A. and Butora, R. and Carey, D. and Costa, A. and Deharveng, L. and Di Giorgio, A. and Eden, D. and Hajnal, A. and Hoare, M. and Kacsuk, P. and Leto, P. and Marsh, K. and Mège, P. and Molinari, S. and Molinaro, M. and Noriega-Crespo, A. and Schisano, E. and Sciacca, E. and Trigilio, C. and Umana, G. and Vitello, F.}, biburl = {https://www.bibsonomy.org/bibtex/20bf113ac5841f133bb5186a7e262ddac/miki}, description = {[1705.09877] Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane}, interhash = {98c7342060885f8ac1da74f54929fe05}, intrahash = {0bf113ac5841f133bb5186a7e262ddac}, keywords = {Galactic HII plane regions}, note = {cite arxiv:1705.09877Comment: 15 pages, 12 figures. Accepted for publication by Astronomy and Astrophysics}, timestamp = {2017-05-30T09:52:56.000+0200}, title = {Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane}, url = {http://arxiv.org/abs/1705.09877}, year = 2017 } @misc{roshi2017helium, abstract = {We present measurements of the singly ionized helium to hydrogen ratio ($n_{He^+}/n_{H^+}$) toward diffuse gas surrounding three Ultra-Compact HII (UCHII ) regions: G10.15-0.34, G23.46-0.20 \& G29.96-0.02. We observe radio recombination lines (RRLs) of hydrogen and helium near 5 GHz using the GBT to measure the $n_{He^+}/n_{H^+}$ ratio. The measurements are motivated by the low helium ionization observed in the warm ionized medium (WIM) and in the inner Galaxy diffuse ionized regions (DIR). Our data indicate that the helium is not uniformly ionized in the three observed sources. Helium lines are not detected toward a few observed positions in sources G10.15-0.34 \& G23.46-0.20 and the upper limits of the $n_{He^+}/n_{H^+}$ ratio obtained are 0.03 and 0.05 respectively. The selected sources harbor stars of type O6 or hotter as indicated by helium line detection toward the bright radio continuum emission from the sources with mean $n_{He^+}/n_{H^+}$ value 0.06$\pm$0.02. Our data thus show that helium in diffuse gas located a few pc away from the young massive stars embedded in the observed regions is not fully ionized.We investigate the origin of the non-uniform helium ionization and rule out the possibilities : (a) that the helium is doubly ionized in the observed regions and (b) that the low $n_{He^+}/n_{H^+}$ values are due to additional hydrogen ionizing radiation produced by accreting low-mass stars (Smith 2014). We find that selective absorption of ionizing photons by dust can result in low helium ionization but needs further investigation to develop a self-consistent model for dust in HII regions.}, added-at = {2017-03-13T12:23:44.000+0100}, author = {Roshi, D. Anish and Churchwell, E. and Anderson, L. D.}, biburl = {https://www.bibsonomy.org/bibtex/2b8a5773874a81f2f0a643773efc3d62e/miki}, description = {[1703.03452] Helium Ionization in the Diffuse Ionized Gas surrounding UCHII regions}, interhash = {e4ced8f7e6682407be97c250a62425e6}, intrahash = {b8a5773874a81f2f0a643773efc3d62e}, keywords = {HII HeII diffuse gas ionized regions}, note = {cite arxiv:1703.03452Comment: 43 pages, 11 figures, 5 tables accepted to ApJ}, timestamp = {2017-03-13T12:23:44.000+0100}, title = {Helium Ionization in the Diffuse Ionized Gas surrounding UCHII regions}, url = {http://arxiv.org/abs/1703.03452}, year = 2017 } @misc{chavez2016constraining, abstract = {We use the HII galaxies $L - \sigma$ relation and the resulting Hubble expansion cosmological probe of a sample of just 25 high-$z$ (up to $z \sim 2.33$) HII galaxies, in a joint likelihood analysis with other well tested cosmological probes (CMB, BAOs) in an attempt to constrain the dark energy equation of state (EoS). The constraints, although still weak, are in excellent agreement with those of a similar joint analysis using the well established SNIa Hubble expansion probe. Interestingly, even with the current small number of available high redshift HII galaxies, the HII/BAO/CMB joint analysis gives a 13% improvement of the quintessence dark energy cosmological constraints compared to the BAO/CMB joint analysis. We have further performed extensive Monte Carlo simulations, with a realistic redshift sampling, to explore the extent to which the use of the $L - \sigma$ relation, observed in HII galaxies, can constrain effectively the parameter space of the dark energy EoS. The simulations predict substantial improvement in the constraints when increasing the sample of high-$z$ HII galaxies to 500, a goal that can be achieved in reasonable observing times with existing large telescopes and state-of-the-art instrumentation.}, added-at = {2016-07-25T10:15:20.000+0200}, author = {Chávez, Ricardo and Plionis, Manolis and Basilakos, Spyros and Terlevich, Roberto and Terlevich, Elena and Melnick, Jorge and Bresolin, Fabio and González-Morán, Ana Luisa}, biburl = {https://www.bibsonomy.org/bibtex/2da015fae238adbe101d9b1fd1528e151/miki}, description = {[1607.06458] Constraining the Dark Energy Equation of State with HII Galaxies}, interhash = {5a85c362f173718b25b42a291b7619e8}, intrahash = {da015fae238adbe101d9b1fd1528e151}, keywords = {HII dark energy equation galaxies state}, note = {cite arxiv:1607.06458Comment: Accepted for publication in MNRAS on 21st July 2016. 10 pages, 5 figures}, timestamp = {2016-07-25T10:15:20.000+0200}, title = {Constraining the Dark Energy Equation of State with HII Galaxies}, url = {http://arxiv.org/abs/1607.06458}, year = 2016 } @misc{relano2016properties, abstract = {The conversion of the IR emission into star formation rate can be strongly dependent on the physical properties of the dust, which are affected by the environmental conditions where the dust is embedded. We study here the dust properties of a set of HII regions in the Local Group Galaxy M33 presenting different spatial configurations between the stars, gas and dust to understand the dust evolution under different environments. We model the SED of each region using the DustEM tool and obtain the mass relative to hydrogen for Very Small Grains (YVSG), Polycyclic Aromatic Hydrocarbons (YPAH) and Big Grains (YBG). The relative mass of the VSGs (YVSG/YTOT) is a factor of 1.7 higher for HII regions classified as filled and mixed than for regions presenting a shell structure. The enhancement of VSGs within NGC 604 and NGC 595 is correlated to expansive gas structures with velocities greater than 50 km/s. The gas-to-dust ratio derived for the HII regions in our sample exhibits two regimes related to the HI-H2 transition of the ISM. Regions corresponding to the HI diffuse regime present a gas-to-dust ratio compatible with the expected value if we assume that the gas-to-dust ratio scales linearly with metallicity, while regions corresponding to a H2 molecular phase present a flatter dust-gas surface density distribution. The fraction of VSGs can be affected by the conditions of the interstellar environment: strong shocks of 50-90 km/s existing in the interior of the most luminous HII regions can lead to fragmentation of BGs into smaller ones, while the more evolved shell and clear shell objects provide a more quiescent environment where reformation of dust BG grains might occur. The gas-to-dust variations found in this analysis might imply that grain coagulation and/or gas-phase metals incorporation to the dust mass is occurring in the interior of the HII regions in M33.}, added-at = {2016-06-14T09:45:25.000+0200}, author = {Relano, M. and Kennicutt, R. and Lisenfeld, U. and Verley, S. and Hermelo, I. and Boquien, M. and Albrecht, M. and Kramer, C. and Braine, J. and Perez-Montero, E. and De Looze, I. and Xilouris, M. and Kovacs, A. and Staguhn, J.}, biburl = {https://www.bibsonomy.org/bibtex/272e53b74a8f85e1832a71815807ac6d6/miki}, description = {[1606.03624] Dust Properties in HII Regions in M33}, interhash = {4677934737bb5fa4471819cb39f9aee8}, intrahash = {72e53b74a8f85e1832a71815807ac6d6}, keywords = {HII dust regions}, note = {cite arxiv:1606.03624Comment: Accepted for publication in A&A, 29 pages, 16 figures}, timestamp = {2016-06-14T09:45:25.000+0200}, title = {Dust Properties in HII Regions in M33}, url = {http://arxiv.org/abs/1606.03624}, year = 2016 } @misc{morisset2016photoionization, abstract = {Photoionization models of HII regions require as input a description of the ionizing SED and of the gas distribution, in terms of ionization parameter U and chemical abundances (e.g. O/H and N/O). A strong degeneracy exists between the hardness of the SED and U, which in turn leads to high uncertainties in the determination of the other parameters, including abundances. One way to resolve the degeneracy is to fix one of the parameters using additional information. For each of the ~ 20000 sources of the CALIFA HII regions catalog, a grid of photoionization models is computed assuming the ionizing SED being described by the underlying stellar population obtained from spectral synthesis modeling. The ionizing SED is then defined as the sum of various stellar bursts of different ages and metallicities. This solves the degeneracy between the shape of the ionizing SED and U. The nebular metallicity (associated to O/H) is defined using the classical strong line method O3N2 (which gives to our models the status of "hybrids"). The remaining free parameters are the abundance ratio N/O and the ionization parameter U, which are determined by looking for the model fitting [NII]/Ha and [OIII]/Hb. The models are also selected to fit [OII]/Hb. This process leads to a set of ~ 3200 models that reproduce simultaneously the three observations. We find that the regions associated to young stellar bursts suffer leaking of the ionizing photons, the proportion of escaping photons having a median of 80\%. The set of photoionization models satisfactorily reproduces the electron temperature derived from the [OIII]4363/5007 line ratio. We determine new relations between the ionization parameter U and the [OII]/[OIII] or [SII]/[SIII] line ratios. New relations between N/O and O/H and between U and O/H are also determined. All the models are publicly available on the 3MdB database.}, added-at = {2016-06-06T10:05:33.000+0200}, author = {Morisset, C. and Delgado-Inglada, G. and Sánchez, S. F. and Galbany, L. and Garcia-Benito, R. and Husemann, B. and Marino, R. A. and Mast, D. and Roth, M. M. and Colaboration, CALIFA}, biburl = {https://www.bibsonomy.org/bibtex/209d0e49489a71180c1eafa2a02b9199a/miki}, description = {[1606.01146] Photoionization models of the CALIFA HII regions. I. Hybrid models}, interhash = {c5f65b56c94bd125452d022bc6d918ca}, intrahash = {09d0e49489a71180c1eafa2a02b9199a}, keywords = {HII models photoionisation regions}, note = {cite arxiv:1606.01146Comment: Accepted for publication in A&A}, timestamp = {2016-06-06T10:05:33.000+0200}, title = {Photoionization models of the CALIFA HII regions. I. Hybrid models}, url = {http://arxiv.org/abs/1606.01146}, year = 2016 } @misc{luisi2016region, abstract = {Using data from the Green Bank Telescope, we analyze the radio continuum (free-free) and radio recombination line (RRL) emission of the compact HII region NGC 7538 (Sharpless 158). We detect extended radio continuum and hydrogen RRL emission beyond the photodissociation region (PDR) toward the north and east, but a sharp decrease in emission toward the south and west. This indicates that a non-uniform PDR morphology is affecting the amount of radiation "leaking" through the PDR. The strongest carbon RRL emission is found in the western PDR that appears to be dense. We compute a leaking fraction $f_R = 15 \pm 5$ % of the radio continuum emission measured in the plane of the sky which represents a lower limit when accounting for the three-dimensional geometry of the region. We detect an average $^4\textrm{He}^+/\textrm{H}^+$ abundance ratio by number of $0.088 \pm 0.003$ inside the HII region and a decrease in this ratio with increasing distance from the region beyond the PDR. Using Herschel Space Observatory data, we show that small dust temperature enhancements to the north and east of NGC 7538 coincide with extended radio emission, but that the dust temperature enhancements are mostly contained within a second PDR to the east. Unlike the giant HII region W43, the radiation leaking from NGC 7538 seems to only affect the local ambient medium. This suggests that giant HII regions may have a large effect in maintaining the ionization of the interstellar medium.}, added-at = {2016-05-10T09:41:33.000+0200}, author = {Luisi, Matteo and Anderson, L. D. and Balser, Dana S. and Bania, T. M. and Wenger, Trey V.}, biburl = {https://www.bibsonomy.org/bibtex/273db88f060bb976114f607669373633b/miki}, description = {[1605.02685] HII Region Ionization of the Interstellar Medium: A Case Study of NGC 7538}, interhash = {a02db537aaf087ae8ec85746fc6b8174}, intrahash = {73db88f060bb976114f607669373633b}, keywords = {HII local radiation region}, note = {cite arxiv:1605.02685Comment: Accepted for publication in ApJ (15 pages, 10 figures, 2 tables)}, timestamp = {2016-05-10T09:41:33.000+0200}, title = {HII Region Ionization of the Interstellar Medium: A Case Study of NGC 7538}, url = {http://arxiv.org/abs/1605.02685}, year = 2016 } @misc{asari2016bayesian, abstract = {We present BOND, a Bayesian code to simultaneously derive oxygen and nitrogen abundances in giant H II regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries. Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of H II regions or the stochastic sampling of the initial mass function. All previous approaches assume a strict relation between the ionizing field and metallicity. The other novelty is extracting information on the nebular physics from semi-strong emission lines. While strong lines ratios alone ([O III]/Hbeta, [O II]/Hbeta and [N II]/Hbeta) lead to multiple O/H solutions, the simultaneous use of [Ar III]/[Ne III] allows one to decide whether an H II region is of high or low metallicity. Adding He I/Hbeta pins down the hardness of the radiation field. We apply our method to H II regions and blue compact dwarf galaxies, and find that the resulting N/O vs O/H relation is as scattered as the one obtained from the temperature-based method. As in previous strong-line methods calibrated on photoionization models, the BOND O/H values are generally higher than temperature-based ones, which might indicate the presence of temperature fluctuations or kappa distributions in real nebulae, or a too soft ionizing radiation field in the models.}, added-at = {2016-05-05T09:48:33.000+0200}, author = {Asari, N. Vale and Stasińska, G. and Morisset, C. and Fernandes, R. Cid}, biburl = {https://www.bibsonomy.org/bibtex/2d216745f4efae09b27371d9d5ee894a9/miki}, description = {[1605.01057] BOND: Bayesian Oxygen and Nitrogen abundance Determinations in giant H II regions using strong and semi-strong lines}, doi = {10.1093/mnras/stw971}, interhash = {9ae3d4984b68357ccc708c0b77219ac7}, intrahash = {d216745f4efae09b27371d9d5ee894a9}, keywords = {HII models regions}, note = {cite arxiv:1605.01057Comment: MNRAS in press; 21 pages, 22 figures, 2 tables; code, data and results available at http://bond.ufsc.br}, timestamp = {2016-05-05T09:48:33.000+0200}, title = {BOND: Bayesian Oxygen and Nitrogen abundance Determinations in giant H II regions using strong and semi-strong lines}, url = {http://arxiv.org/abs/1605.01057}, year = 2016 } @misc{kreckel2016characterizing, abstract = {Interarm star formation contributes significantly to a galaxy's star formation budget, and provides an opportunity to study stellar birthplaces unperturbed by spiral arm dynamics. Using optical integral field spectroscopy of the nearby galaxy NGC 628 with VLT/MUSE, we identify 391 HII regions at 35pc resolution over 12 kpc^2. Using tracers sensitive to the underlying gravitational potential, we associate HII regions with either arm (271) or interarm (120) environments. We find that most HII region physical properties (luminosity, size, metallicity, ionization parameter) are independent of environment. We calculate the fraction of Halpha luminosity due to the diffuse ionized gas (DIG) background contaminating each HII region, and find the DIG surface brightness to be higher within HII regions compared to the surroundings, and slightly higher within arm HII regions. Use of the temperature sensitive [SII]/Halpha line ratio map instead of the Halpha surface brightness to identify HII region boundaries does not change this result. Using the dust attenuation as a tracer of the gas, we find relatively short depletion times (6 x 10^8 yr) with no differences between the arm and interarm, however this is very sensitive to the DIG correction. Unlike molecular clouds, which can be dynamically affected by the galactic environment, we see fairly consistent HII region properties in both arm and interarm environments. This suggests either a difference in arm star formation and feedback, or a decoupling of dense star forming clumps from the more extended surrounding molecular gas.}, added-at = {2016-03-29T10:10:56.000+0200}, author = {Kreckel, K. and Blanc, G. A. and Schinnerer, E. and Groves, B. and Adamo, A. and Hughes, A. and Meidt, S.}, biburl = {https://www.bibsonomy.org/bibtex/2e799193370cb75c720fda45a3723de3c/miki}, description = {[1603.08009] Characterizing spiral arm and interarm star formation}, interhash = {fa172a0ae82dd30edff0cc9c25a506b1}, intrahash = {e799193370cb75c720fda45a3723de3c}, keywords = {HII arm interarm region}, note = {cite arxiv:1603.08009Comment: 8 pages, 4 figures, 1 table, submitted to ApJ Letters}, timestamp = {2016-03-29T10:10:56.000+0200}, title = {Characterizing spiral arm and interarm star formation}, url = {http://arxiv.org/abs/1603.08009}, year = 2016 } @misc{mackey2015detecting, abstract = {Mid-infrared arcs of dust emission are often seen near ionizing stars within HII regions. A possible explanations for these arcs is that they could show the outer edges of asymmetric stellar wind bubbles. We use two-dimensional, radiation-hydrodynamics simulations of wind bubbles within HII regions around individual stars to predict the infrared emission properties of the dust within the HII region. We assume that dust and gas are dynamically well-coupled and that dust properties (composition, size distribution) are the same in the HII region as outside it, and that the wind bubble contains no dust. We post-process the simulations to make synthetic intensity maps at infrared wavebands using the TORUS code. We find that the outer edge of a wind bubble emits brightly at 24um through starlight absorbed by dust grains and re-radiated thermally in the infrared. This produces a bright arc of emission for slowly moving stars that have asymmetric wind bubbles, even for cases where there is no bow shock or any corresponding feature in tracers of gas emission. The 24um intensity decreases exponentially from the arc with increasing distance from the star because the dust temperature decreases with distance. The size distribution and composition of the dust grains has quantitative but not qualitative effects on our results. Despite the simplifications of our model, we find good qualitative agreement with observations of the HII region RCW120, and can provide physical explanations for any quantitative differences. Our model produces an infrared arc with the same shape and size as the arc around CD -38 11636 in RCW120, and with comparable brightness. This suggests that infrared arcs around O stars in HII regions may be revealing the extent of stellar wind bubbles, although we have not excluded other explanations.}, added-at = {2015-12-23T08:22:48.000+0100}, author = {Mackey, Jonathan and Haworth, Thomas J. and Gvaramadze, Vasilii V. and Mohamed, Shazrene and Langer, Norbert and Harries, Tim J.}, biburl = {https://www.bibsonomy.org/bibtex/2bc8a36a613b664655322faf4a96c268b/miki}, description = {[1512.06857] Detecting stellar-wind bubbles through infrared arcs in HII regions}, interhash = {7d6ba278b9c926e17ecb2abc3e4ac1f5}, intrahash = {bc8a36a613b664655322faf4a96c268b}, keywords = {HII dust ionization regions}, note = {cite arxiv:1512.06857Comment: 16 pages, 11 figures, accepted for publication in Astronomy & Astrophysics}, timestamp = {2015-12-23T08:22:48.000+0100}, title = {Detecting stellar-wind bubbles through infrared arcs in HII regions}, url = {http://arxiv.org/abs/1512.06857}, year = 2015 } @misc{tanaka2015outflowconfined, abstract = {We present an evolutionary sequence of models of the photoionized disk-wind outflow around forming massive stars based on the Core Accretion model. The outflow is expected to be the first structure to be ionized by the protostar and can confine the expansion of the H II region, especially in lateral directions in the plane of the accretion disk. The ionizing luminosity increases as Kelvin-Helmholz contraction proceeds, and the H II region is formed when the stellar mass reaches $\sim\:10$ - $20\:M_\odot$ depending on the initial cloud core properties. Although some part of outer disk surface remains neutral due to shielding by the inner disk and the disk wind, almost the whole of the outflow is ionized in $10^3$ - $10^4\:{\rm yr}$ after initial H II region formation. Having calculated the extent and temperature structure of the H II region within the immediate protostellar environment, we then make predictions for the strength of its free-free continuum and recombination line emission. The free-free radio emission from the ionized outflow has a flux density of $\sim5$ - $50\:(\nu/{\rm GHz})^p{\rm\:mJy\:kpc^2}$ with a spectral index $p = 0.6 - 0.9$, and the apparent size is typically $\sim\:1000\:\rm AU$ at 1 GHz. The H40$\alpha$ line profile has a width of about $100\:{\rm km\:s^{-1}}$. These properties of our model are consistent with observed radio winds and jets around forming massive protostars.}, added-at = {2015-09-24T10:26:37.000+0200}, author = {Tanaka, Kei E. I. and Tan, Jonathan C. and Zhang, Yichen}, biburl = {https://www.bibsonomy.org/bibtex/25c81d7645b79b1260cb9388e6806edeb/miki}, description = {[1509.06754] Outflow-Confined H II Regions. I. First Signposts of Massive Star Formation}, interhash = {a18c9d50fa451af0a5c67e355cd644f6}, intrahash = {5c81d7645b79b1260cb9388e6806edeb}, keywords = {HII expansion outflowing regions}, note = {cite arxiv:1509.06754Comment: 18 pages, 17 figures, submitted to ApJ}, timestamp = {2015-09-24T10:26:37.000+0200}, title = {Outflow-Confined H II Regions. I. First Signposts of Massive Star Formation}, url = {http://arxiv.org/abs/1509.06754}, year = 2015 } @misc{haworth2015relative, abstract = {Radiation hydrodynamics (RHD) simulations are used to study many astrophysical phenomena, however they require the use of simplified radiation transport and thermal prescriptions to reduce computational cost. In this paper we present a systematic study of the importance of microphysical processes in RHD simulations using the example of D-type HII region expansion. We compare the simplest hydrogen-only models with those that include: ionisation of H, He, C, N, O, S and Ne, different gas metallicity, non-LTE metal line blanketed stellar spectral models of varying metallicity, radiation pressure, dust and treatment of photodissociation regions. Each of these processes are explicitly treated using modern numerical methods rather than parameterisation. In line with expectations, changes due to microphysics in either the effective number of ionising photons or the thermal structure of the gas lead to differences in D-type expansion. In general we find that more realistic calculations lead to the onset of D-type expansion at smaller radii and a slower subsequent expansion. Simulations of star forming regions using simplified microphysics are therefore likely overestimating the strength of radiative feedback. We find that both variations in gas metallicity and the inclusion of dust can affect the ionisation front evolution at the 10-20 per cent level over 500kyr, which could substantially modify the results of simplified 3D models including feedback. Stellar metallicity, radiation pressure and the inclusion of photodissociation regions are all less significant effects at the 1 per cent level or less, rendering them of minor importance in the modelling the dynamical evolution of HII regions.}, added-at = {2015-08-06T09:55:34.000+0200}, author = {Haworth, Thomas J. and Harries, Tim J. and Acreman, David M. and Bisbas, Thomas G.}, biburl = {https://www.bibsonomy.org/bibtex/22b82e667dacce204252c79cb6d4063a4/miki}, description = {[1508.00900] On the relative importance of different microphysics on the D-type expansion of galactic HII regions}, interhash = {0a316216d02f9f2346ab24f01ecfd77b}, intrahash = {2b82e667dacce204252c79cb6d4063a4}, keywords = {HII ionisation regions}, note = {cite arxiv:1508.00900Comment: 14 pages, 9 figures, accepted for publication in the MNRAS main journal}, timestamp = {2015-08-06T09:55:34.000+0200}, title = {On the relative importance of different microphysics on the D-type expansion of galactic HII regions}, url = {http://arxiv.org/abs/1508.00900}, year = 2015 } @misc{bisbas2015starbench, abstract = {StarBench is a project focused on benchmarking and validating different star-formation and stellar feedback codes. In this first StarBench paper we perform a comparison study of the D-type expansion of an HII region. The aim of this work is to understand the differences observed between the twelve participating numerical codes against the various analytical expressions examining the D-type phase of HII region expansion. To do this, we propose two well-defined tests which are tackled by 1D and 3D grid- and SPH- based codes. The first test examines the `early phase' D-type scenario during which the mechanical pressure driving the expansion is significantly larger than the thermal pressure of the neutral medium. The second test examines the `late phase' D-type scenario during which the system relaxes to pressure equilibrium with the external medium. Although they are mutually in excellent agreement, all twelve participating codes follow a modified expansion law that deviates significantly from the classical Spitzer solution in both scenarios. We present a semi-empirical formula combining the two different solutions appropriate to both early and late phases that agrees with high-resolution simulations to $\lesssim2\%$. This formula provides a much better benchmark solution for code validation than the Spitzer solution. The present comparison has validated the participating codes and through this project we provide a dataset for calibrating the treatment of ionizing radiation hydrodynamics codes.}, added-at = {2015-07-22T09:48:31.000+0200}, author = {Bisbas, T. G. and Haworth, T. J. and Williams, R. J. R. and Mackey, J. and Tremblin, P. and Raga, A. C. and Arthur, S. J. and Baczynski, C. and Dale, J. E. and Frostholm, T. and Geen, S. and Haugboelle, T. and Hubber, D. and Iliev, I. T. and Kuiper, R. and Rosdahl, J. and Sullivan, D. and Walch, S. and Wuensch, R.}, biburl = {https://www.bibsonomy.org/bibtex/2736be2caef66f20caf49efd94de08d88/miki}, description = {[1507.05621] StarBench: The D-type expansion of an HII region}, interhash = {93e0efffeac563ec7374ec793aea6bf1}, intrahash = {736be2caef66f20caf49efd94de08d88}, keywords = {HII code comparison expansion region}, note = {cite arxiv:1507.05621Comment: 20 pages, 12 Figures, 4 Tables. Accepted for publication in MNRAS. Comments are welcome. Participation in future StarBench tests is also welcome}, timestamp = {2015-07-22T09:48:31.000+0200}, title = {StarBench: The D-type expansion of an HII region}, url = {http://arxiv.org/abs/1507.05621}, year = 2015 } @misc{sanchez2014census, abstract = {We present a study of the HII regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197,637 individual spectra, using Integral Field Spectrocopy (IFS) recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ~2 effective radii (re ), sampling its morphological structures with unprecedented spatial resolution for a wide-field IFU. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogue of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allow us to estimate the typical mixing scale-length (rmix ~0.4 re ), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms, when comparing with simulations. We found evidence for an azimuthal variation of the oxygen abundance, that may be related with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.}, added-at = {2014-11-19T10:12:14.000+0100}, author = {Sánchez, S. F. and Galbany, L. and Pérez, E. and Sánchez-Blázquez, P. and Falcón-Barroso, J. and Rosales-Ortega, F. F. and Sánchez-Menguiano, L. and Marino, R. and Kuncarayakti, H. and Anderson, J. P. and Kruehler, T. and Cano-Díaz, M. and Barrera-Ballesteros, J. K. and González-González, J. J.}, biburl = {https://www.bibsonomy.org/bibtex/2f6f9f9e5bf86fc2c9e6fcc2a0cf1a592/miki}, description = {[1411.4967] Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale}, interhash = {73b2fae421b035c93e768e9d40ede39d}, intrahash = {f6f9f9e5bf86fc2c9e6fcc2a0cf1a592}, keywords = {hii metal mixing muse regions}, note = {cite arxiv:1411.4967Comment: 13 pages, 7 Figurs, accepted for publishing in A&A}, timestamp = {2014-11-19T10:12:14.000+0100}, title = {Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale}, url = {http://arxiv.org/abs/1411.4967}, year = 2014 } @misc{tremblin2014position, abstract = {This work aims at improving the current understanding of the interaction between H ii regions and turbulent molecular clouds. We propose a new method to determine the age of a large sample of OB associations by investigating the development of their associated H ii regions in the surrounding turbulent medium. Using analytical solutions, one-dimensional (1D), and three-dimensional (3D) simulations, we constrained the expansion of the ionized bubble depending on the turbulent level of the parent molecular cloud. A grid of 1D simulations was then computed in order to build isochrone curves for H ii regions in a pressure-size diagram. This grid of models allowed to date large sample of OB associations and was used on the H ii Region Discovery Survey (HRDS). Analytical solutions and numerical simulations showed that the expansion of H ii regions is slowed down by the turbulence up to the point where the pressure of the ionized gas is in a quasi-equilibrium with the turbulent ram pressure. Based on this result, we built a grid of 1D models of the expansion of H ii regions in a profile based on Larson laws. The 3D turbulence is taken into account by an effective 1D temperature profile. The ages estimated by the isochrones of this grid agree well with literature values of well-known regions such as Rosette, RCW 36, RCW 79, and M16. We thus propose that this method can be used to give ages of young OB associations through the Galaxy such as the HRDS survey and also in nearby extra-galactic sources.}, added-at = {2014-06-10T09:49:05.000+0200}, author = {Tremblin, P. and Anderson, L. D. and Didelon, P. and Raga, A. C. and Minier, V. and Ntormousi, E. and Pettitt, A. and Pinto, C. and Samal, M. and Schneider, N. and Zavagno, A.}, biburl = {https://www.bibsonomy.org/bibtex/2ec82713808b3125aa9c8ef29eeaf91ac/miki}, description = {[1406.1801] Age, size, and position of H ii regions in the Galaxy. Expansion of ionized gas in turbulent molecular clouds}, interhash = {e6595d69c4a4f21ec13b7770f1dbd977}, intrahash = {ec82713808b3125aa9c8ef29eeaf91ac}, keywords = {hii regions size}, note = {cite arxiv:1406.1801Comment: Accepted in A&A}, timestamp = {2014-06-10T09:49:05.000+0200}, title = {Age, size, and position of H ii regions in the Galaxy. Expansion of ionized gas in turbulent molecular clouds}, url = {http://arxiv.org/abs/1406.1801}, year = 2014 } @misc{dessaugeszavadsky2014steep, abstract = {Results from the UV satellite GALEX revealed large extensions of disks in some nearby spiral galaxies, extending out to 3 to 4 times the isophotal radius, r25. M63 is a remarkable example of a spiral galaxy with one of the most extended UV disks, so it offers the opportunity to search for the molecular gas and characterize the star formation in outer disk regions as revealed by the UV emission. We obtained deep CO(1-0) and CO(2-1) observations on the IRAM 30 m telescope along the major axis of the M63 disk from the center out to the galactocentric radius rgal = 1.6 r25 and over a bright UV region at rgal = 1.36 r25. CO(1-0) is detected all along the M63 major axis out to r25, and CO(2-1) is confined to rgal = 0.68 r25, which may betray lower excitation temperatures in the outer disk. CO(1-0) is also detected in the external bright UV region of M63. The radial profiles of the CO emission and of the Halpha, 24 micron, NUV and FUV star formation tracers and HI taken from the literature show a severe drop with the galactocentric radius, such that beyond r25 they are all absent with the exception of a faint UV emission and HI. The CO emission detection in the external UV region, where the UV flux is higher than the UV flux observed beyond r25, highlights a tight correlation between the CO and UV fluxes, namely the amount of molecular gas and the intensity of star formation. This external UV region is dominated by the atomic gas, suggesting that HI is more likely the precursor of H2 rather than the product of UV photodissociation. A broken power law needs to be invoked to describe the Kennicutt-Schmidt (K-S) relation of M63 from the center of the galaxy out to rgal = 1.36 r25. While all along the major axis out to r25 the K-S relation is almost linear, in the external UV region the SFR regime is highly nonlinear and characterized by a steep K-S relation and very low star formation efficiency.}, added-at = {2014-06-03T09:48:40.000+0200}, author = {Dessauges-Zavadsky, M. and Verdugo, C. and Combes, F. and Pfenniger, D.}, biburl = {https://www.bibsonomy.org/bibtex/2b426581b999cf674e2c9d62f203d0176/miki}, description = {[1406.0310] CO map and steep Kennicutt-Schmidt relation in the extended UV disk of M63}, interhash = {5d96cad29d5d49cef7b23bff11e0851b}, intrahash = {b426581b999cf674e2c9d62f203d0176}, keywords = {UV co disks extended hii}, note = {cite arxiv:1406.0310Comment: 12 pages, 8 figures, A&A accepted}, timestamp = {2014-06-03T09:48:40.000+0200}, title = {CO map and steep Kennicutt-Schmidt relation in the extended UV disk of M63}, url = {http://arxiv.org/abs/1406.0310}, year = 2014 } @misc{nicholls2014metalpoor, abstract = {In this paper, we use the Mappings photoionization code to explore the physical parameters that impact on the measurement of electron temperature and abundance in HII regions. In the previous paper we presented observations and measurements of physical properties from the spectra of seventeen HII regions in fourteen isolated dwarf irregular galaxies from the SIGRID sample. Here, we analyze these observations further, together with three additional published data sets. We explore the effects of optical thickness, electron density, ionization parameter, ionization source, and non-equilibrium effects on the relation between electron temperature and metallicity. We present a standard model that fits the observed data remarkably well at metallicities between 1/10 and 1 solar. We investigate the effects of optically thin HII regions, and show that they can have a considerable effect on the measured electron temperature, and that there is evidence that some of the observed objects are optically thin. We look at the role of the ionization parameter and find that lower ionization parameter values give better fits at higher oxygen abundance. We show that higher pressures combined with low optical depth, and also kappa electron energy distributions at low kappa values, can generate the apparent high electron temperatures in low metallicity HII regions, and that the former provides the better fit to observations. We examine the effects of these parameters on the strong line diagnostic methods. We extend this to three-dimensional diagnostic grids to confirm how well the observations are described by the grids.}, added-at = {2014-05-29T14:44:16.000+0200}, author = {Nicholls, David C. and Dopita, Michael A. and Sutherland, Ralph S. and Jerjen, Helmut and Kewley, Lisa J. and Basurah, Hassan}, biburl = {https://www.bibsonomy.org/bibtex/256e0f561c4c0748fed37a4d7d2093caa/miki}, description = {[1405.7170] Metal-poor dwarf galaxies in the SIGRID galaxy sample. II. The electron temperature-abundance calibration and the parameters that affect it}, interhash = {bdea28940e091a703ba362a387ba5557}, intrahash = {56e0f561c4c0748fed37a4d7d2093caa}, keywords = {calibration hii metallicity photoionisation regions}, note = {cite arxiv:1405.7170Comment: Accepted for publication in The Astrophysical Journal. 17 figures, 50 pages}, timestamp = {2014-05-29T14:44:16.000+0200}, title = {Metal-poor dwarf galaxies in the SIGRID galaxy sample. II. The electron temperature-abundance calibration and the parameters that affect it}, url = {http://arxiv.org/abs/1405.7170}, year = 2014 } @misc{dale2014before, abstract = {We model the combined effects of photoionization and momentum--driven winds from O--stars on molecular clouds spanning a parameter space of initial conditions. The dynamical effects of the winds are very modest. However, in the lower--mass clouds, they influence the morphologies of the HII regions by creating 10pc--scale central cavities.\\ The inhomogeneous structures of the model GMCs make them highly permeable to photons, ionized gas and supernova ejecta, and the leaking of ionized gas in particular strongly affects their evolution, reducing the effectiveness of feedback. Nevertheless, feedback is able to expel large fractions of the mass of the lower escape--velocity clouds. Its impact on star formation is more modest, decreasing final star formation efficiencies by 10--20$\%$, and the rate of change of the star formation efficiency per freefall time by about one third. However, the clouds still form stars substantially faster than observed GMCs.}, added-at = {2014-04-25T09:46:50.000+0200}, author = {Dale, J. E. and Ngoumou, J. and Ercolano, B. and Bonnell, I. A.}, biburl = {https://www.bibsonomy.org/bibtex/2386f783fab1ace80ac2a4b63c7f26164/miki}, description = {[1404.6102] Before the first supernova: combined effects of HII regions and winds on molecular clouds}, interhash = {64c77f314b4487931dc035fc093da06e}, intrahash = {386f783fab1ace80ac2a4b63c7f26164}, keywords = {gmc hii regions supernova}, note = {cite arxiv:1404.6102Comment: 21 pages, 19 figures, accepted for publication in MNRAS}, timestamp = {2014-04-25T09:46:50.000+0200}, title = {Before the first supernova: combined effects of HII regions and winds on molecular clouds}, url = {http://arxiv.org/abs/1404.6102}, year = 2014 }