scholarly journals Internal kinematics of giant H ii regions in M101 with the Keck Cosmic Web Imager

2020 ◽  
Vol 495 (4) ◽  
pp. 4347-4365 ◽  
Author(s):  
Fabio Bresolin ◽  
Luca Rizzi ◽  
I-Ting Ho ◽  
Roberto Terlevich ◽  
Elena Terlevich ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Large Fraction ◽  
H Ii Regions ◽  
Line Profiles ◽  
Radiative Shock ◽  
Star Forming ◽  
The Galaxy ◽  
Low Metallicity ◽  
The Individual ◽  
Expanding Shells

ABSTRACT We study the kinematics of the giant H ii regions NGC 5455 and NGC 5471 located in the galaxy M101, using integral field observations that include the H β and [O iii]$\, \lambda$ 5007 emission lines, obtained with the Keck Cosmic Web Imager. We analyse the line profiles using both single and multiple Gaussian curves, gathering evidence for the presence of several expanding shells and moving filaments. The line decomposition shows that a broad (σ ≃ 30–50 km s−1) underlying component is ubiquitous, extending across hundreds of pc, while a large fraction of the narrow components have subsonic line widths. The supersonic turbulence inferred from the global line profiles is consistent with the velocity dispersion of the individual narrow components, i.e. the global profiles likely arise from the combined contribution of discrete gas clouds. We confirm the presence of very extended (400–1200 km s−1) low-intensity line components in three bright star-forming cores in NGC 5471, possibly representing kinematic signatures of supernova remnants. For one of these, the known supernova remnant host NGC 5471 B, we find a significantly reduced [O iii]/H β line ratio relative to the surrounding photoionized gas, due to the presence of a radiative shock at low metallicity. We explore the systematic width discrepancy between H i and [O iii] lines, present in both global and individual spaxel spectra. We argue that the resolution of this long-standing problem lies in the physics of the line-emitting gas rather than in the smearing effects induced by the different thermal widths.

scholarly journals The nuclear region of NGC 613 – I. Multiwavelength analysis

2020 ◽  
Vol 492 (4) ◽  
pp. 5121-5140 ◽  
Author(s):  
Patrícia da Silva ◽  
R B Menezes ◽  
J E Steiner
Keyword(s):  
Supernova Remnants ◽  
Near Infrared ◽  
H Ii Regions ◽  
Nuclear Region ◽  
Radio Telescopes ◽  
X Ray ◽  
Star Forming ◽  
Dust Extinction ◽  
The Galaxy ◽  
Variable Point

ABSTRACT In this paper, we report a detailed study with a variety of data from optical, near-infrared, X-ray, and radio telescopes of the nuclear region of the galaxy NGC 613 with the aim of understanding its complexity. We detected an extended stellar emission in the nucleus that, at first, appears to be, in the optical band, two stellar nuclei separated by a stream of dust. The active galactic nucleus (AGN) is identified as a variable point-like source between these two stellar components. There is a central hard X-ray emission and an extended soft X-ray emission that closely coincides with the ionization cone, as seen in the [O iii]λ5007 emission. The centroid of the [O i]λ6300 emission does not coincide with the AGN, being shifted by 0.24 arcsec towards the ionization cone; this shift is probably caused by a combination of differential dust extinction together with emission and reflection in the ionization cone. The optical spectra extracted from the central region are typical of low-ionization nuclear emission-line regions. We also identify 10 H ii regions, eight of them in a star-forming ring that is visible in Br γ, [Fe ii]λ16436, and molecular CO(3-2) images observed in previous studies. Such a ring also presents weak hard X-ray emission, probably associated with supernova remnants, not detected in other studies. The position of the AGN coincides with the centre of a nuclear spiral (detected in previous works) that brings gas and dust from the bar to the nucleus, causing the high extinction in this area.

scholarly journals Giant Molecular Clouds in the Galaxy: The Massachusetts-Stony Brook CO Galactic Plane Survey

1987 ◽  
Vol 115 ◽  
pp. 499-499 ◽  
Author(s):  
P. M. Solomon
Keyword(s):  
Molecular Clouds ◽  
Galactic Plane ◽  
Far Infrared ◽  
Formation Mechanisms ◽  
H Ii Regions ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
Two Populations ◽  
Spiral Arm

The CO Galactic Plane Survey consists of 40,572 spectral line observations in the region between 1 = 8° to 90° and b = −1°.05 to +1°.05 spaced every 3 arc minutes, carried out with the FCRAO 14-m antenna. The velocity coverage from −100 to +200 km/s includes emission from all galactic radii. This high resolution survey was designed to observe and identify essentially all molecular clouds or cloud components larger than 10 parsecs in the inner galaxy. There are two populations of molecular clouds which separate according to temperature. The warm clouds are closely associated with H II regions, exhibit a non-axisymmetric galactic distribution and are a spiral arm population. The cold clouds are a disk population, are not confined to any patterns in longitude-velocity space and must be widespread in the galaxy both in and out of spiral arms. The correlation between far infrared luminosities from IRAS, and molecular masses from CO is utilized to determine a luminosity to mass ratio for the clouds. A face-on picture of the galaxy locating the warm population is presented, showing ring like or spiral arm features at R ∼ 5, 7.5 and 9 kpc. The cloud size and mass spectrum will be discussed and evidence presented showing the presence of clusters of giant molecular clouds with masses of 106 to 107 M⊙. The two populations of clouds probably have different star forming luminosity functions. The implication of the two populations for star formation mechanisms will be discussed.

scholarly journals The Diffuse Ionised Gas in NGC 4449

1998 ◽  
Vol 15 (1) ◽  
pp. 103-105 ◽  
Author(s):  
C. Muñoz-Tuñón ◽  
O. Fuentes-Masip ◽  
H. O. Castañeda
Keyword(s):  
Large Population ◽  
Star Forming ◽  
Star Forming Regions ◽  
La Palma ◽  
Total Luminosity ◽  
Spatial Coverage ◽  
The Galaxy ◽  
Uv Photons ◽  
Set Up ◽  
The Individual

AbstractIt is now well established that there is a diffuse ionised medium which extends far beyond the disks of spirals. The mechanism responsible for the ionisation is still an issue of debate, and the method of measuring the total luminosity, independently of the observational set-up, has to be defined. Here we analyse the case of the Magellanic irregular NGC 4449, using Fabry–Perot bidimensional mapping of the Hα emission line, at the 4·2 m William Herschel Telescope (WHT) telescope on La Palma, Canary Islands. The total spatial coverage of 80×80 arcsec2 allows most of the star forming regions to be sampled at 0·26 arcsec/pixel spatial resolution. Using 3D spectroscopy, it is possible to define the individual star-forming regions and to produce a luminosity versus size diagram. This can be used to estimate directly the number of photons leaking out from those regions exceeding the thickness of the galactic disc. In the case of NGC 4449 it is shown that the large population of GEHRs can be the source of UV photons ionising the diffuse ionised gas (DIG) of the galaxy, and the logL–R diagram can be used to quantify the number of photons leaking out of the material surrounding the star forming regions. In the case of NGC 4449 it is found that 54% of the total luminosity of the giant star-forming regions is lost to the DIG. This implies a contribution of 3·12×1040 erg s−1 (1 erg s−1 = 10−7 J s−1) which amounts to 30% of the galaxy total Hα luminosity.

scholarly journals Fast molecular outflow from a dusty star-forming galaxy in the early Universe

Science ◽  
2018 ◽  
Vol 361 (6406) ◽  
pp. 1016-1019 ◽  
Author(s):  
J. S. Spilker ◽  
M. Aravena ◽  
M. Béthermin ◽  
S. C. Chapman ◽  
C.-C. Chen ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Large Fraction ◽  
Formation Rate ◽  
Free Fall ◽  
Big Bang ◽  
Star Forming ◽  
Molecular Outflow ◽  
The Galaxy ◽  
The Big Bang

Galaxies grow inefficiently, with only a small percentage of the available gas converted into stars each free-fall time. Feedback processes, such as outflowing winds driven by radiation pressure, supernovae, or supermassive black hole accretion, can act to halt star formation if they heat or expel the gas supply. We report a molecular outflow launched from a dust-rich star-forming galaxy at redshift 5.3, 1 billion years after the Big Bang. The outflow reaches velocities up to 800 kilometers per second relative to the galaxy, is resolved into multiple clumps, and carries mass at a rate within a factor of 2 of the star formation rate. Our results show that molecular outflows can remove a large fraction of the gas available for star formation from galaxies at high redshift.

scholarly journals Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements and Adopted Distances

2020 ◽  
Author(s):  
Gagandeep S Anand ◽  
Janice C Lee ◽  
Schuyler D Van Dyk ◽  
Adam K Leroy ◽  
Erik Rosolowsky ◽  
...  
Keyword(s):  
First Year ◽  
Physical Parameters ◽  
H Ii Regions ◽  
Star Clusters And Associations ◽  
Distance Measurements ◽  
Nearby Star ◽  
Star Forming ◽  
Public Data ◽  
The Galaxy ◽  
Red Giant

Abstract PHANGS-HST is an ultraviolet-optical imaging survey of 38 spiral galaxies within ∼20 Mpc. Combined with the PHANGS-ALMA, PHANGS-MUSE surveys and other multiwavelength data, the dataset will provide an unprecedented look into the connections between young stars, H ii regions, and cold molecular gas in these nearby star-forming galaxies. Accurate distances are needed to transform measured observables into physical parameters (e.g., brightness to luminosity, angular to physical sizes of molecular clouds, star clusters and associations). PHANGS-HST has obtained parallel ACS imaging of the galaxy halos in the F606W and F814W bands. Where possible, we use these parallel fields to derive tip of the red giant branch (TRGB) distances to these galaxies. In this paper, we present TRGB distances for 11 galaxies from ∼4 to ∼15 Mpc, based on the first year of PHANGS-HST observations. Five of these represent the first published TRGB distance measurements (IC 5332, NGC 2835, NGC 4298, NGC 4321, and NGC 4328), and eight of which are the best available distances to these targets. We also provide a compilation of distances for the 118 galaxies in the full PHANGS sample, which have been adopted for the first PHANGS-ALMA public data release.

scholarly journals Molecular line ratio diagnostics along the radial cut and dusty ultraviolet-bright clumps in a spiral galaxy NGC 0628

2020 ◽  
Vol 495 (3) ◽  
pp. 2682-2712
Author(s):  
Selçuk Topal
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Line Ratio ◽  
H Ii Regions ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
Star Formation In Galaxies ◽  
Molecular Lines ◽  
Co Gas

ABSTRACT Molecular emission lines are essential tools to shed light on many questions regarding star formation in galaxies. Multiple molecular lines are particularly useful to probe different phases of star-forming molecular clouds. In this study, we investigate the physical properties of giant molecular clouds (GMCs) using multiple lines of CO, i.e. CO(1–0, 2–1, 3–2) and 13CO(1–0), obtained at selected 20 positions in the disc of NGC 0628. A total of 11 positions were selected over the radial cut, including the centre, and remaining 9 positions were selected across the southern and northern arms of the galaxy. A total of 13 out of 20 positions are brighter at $24\, \mu {\rm m}$ and ultraviolet (UV) emission and hosting significantly more H ii regions compared to the rest of the positions indicating opposite characteristics. Our line ratio analysis shows that the gas gets warmer and thinner as a function of radius from the galaxy centre up to 1.7 kpc, and then the ratios start to fluctuate. Our empirical and model results suggest that the UV-bright positions have colder and thinner CO gas with higher hydrogen and CO column densities. However, the UV-dim positions have relatively warmer CO gas with lower densities bathed in GMCs surrounded by less number of H ii regions. Analysis of multiwavelength infrared and UV data indicates that the UV-bright positions have higher star formation efficiency than that of the UV-dim positions.

scholarly journals Optical Observations of four Balmer-Dominated Supernova Remnants in the Large Magellanic Cloud

1983 ◽  
Vol 101 ◽  
pp. 559-565
Author(s):  
I. R. Tuohy ◽  
M. A. Dopita ◽  
D. S. Mathewson ◽  
K. S. Long ◽  
D. J. Helfand
Keyword(s):  
Supernova Remnants ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Optical Observations ◽  
Type I ◽  
Radiative Shock ◽  
Neutral Gas ◽  
The Galaxy ◽  
Hα Emission ◽  
Very High

We report the optical identification of four Balmer-dominated supernova remnants (SNRs) in the Large Magellanic Cloud. Both the Balmer-dominated spectra and the presence of a broad Hα component in one remnant can be understood in terms of a very high velocity non-radiative shock encountering gas which is partially neutral, as proposed originally by Chevalier and Raymond to account for the similar spectra of the galactic remnants, Tycho and SN1006. From a consideration of the optical and X-ray luminosities of the SNR with broad Hα emission, we infer that the fraction of neutral gas in the medium is ≲ 30%. Radio observations of the LMC remnants show that their surface brightnesses are anomalously low; this could be intrinsic to the supernova themselves, or a result of their environment. Finally, we argue that the four SNRs all resulted from Type I supernovae, in which case they are the first such remnants to be identified outside the Galaxy.

scholarly journals Clues on Arp 142: The spiral–elliptical merger

2019 ◽  
Vol 488 (1) ◽  
pp. 830-846
Author(s):  
Marcelo D Mora ◽  
Sergio Torres-Flores ◽  
Verónica Firpo ◽  
Jose A Hernandez-Jimenez ◽  
Fernanda Urrutia-Viscarra ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Morphological Characteristics ◽  
Current Data ◽  
Ionization Mechanism ◽  
H Ii Regions ◽  
Data Set ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Individual

Abstract Nearby merging pairs are unique laboratories in which one can study the gravitational effects on the individual interacting components. In this manuscript, we report the characterization of selected H ii regions along the peculiar galaxy NGC 2936, member of the galaxy pair Arp 142, an E+S interaction, known as ‘The Penguin’. Using Gemini South spectroscopy, we have derived a high enhancement of the global star formation rate (SFR) = 35.9 M⊙ yr−1 probably stimulated by the interaction. Star-forming regions on this galaxy display oxygen abundances that are consistent with solar metallicities. The current data set does not allow us to conclude any clear scenario for NGC 2936. Diagnostic diagrams suggest that the central region of NGC 2936 is ionized by active galactic nucleus (AGN) activity and the eastern tidal plume in NGC 2936 is experiencing a burst of star formation, which may be triggered by the gas compression due to the interaction event with its elliptical companion galaxy: NGC 2937. The ionization mechanism of these sources is consistent with shock models of low velocities of 200–300 km s −1. The isophotal analysis shows tidal features on NGC 2937: at inner radii non-concentric (or off-centring) isophotes, and at large radii, a faint excess of the surface brightness profile with respect to de Vaucouleurs law. By comparing the radial velocity profiles and morphological characteristics of Arp 142 with a library of numerical simulations, we conclude that the current stage of the system would be about 50 ± 25 Myr after the first pericentre passage.

scholarly journals The ALPINE-ALMA [CII] survey

2020 ◽  
Vol 643 ◽  
pp. A7
Author(s):  
M. Ginolfi ◽  
G. C. Jones ◽  
M. Béthermin ◽  
A. Faisst ◽  
B. C. Lemaux ◽  
...  
Keyword(s):  
Decomposition Analysis ◽  
Far Infrared ◽  
Ancillary Data ◽  
Interstellar Gas ◽  
Star Forming ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Major Merger ◽  
Continuum Data ◽  
The Individual

We present ALMA observations of a merging system at z ∼ 4.57, observed as a part of the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) survey. Combining ALMA [CII]158 μm and far-infrared continuum data with multi-wavelength ancillary data, we find that the system is composed of two massive (M⋆ ≳ 1010 M⊙) star-forming galaxies experiencing a major merger (stellar mass ratio rmass ≳ 0.9) at close spatial (∼13 kpc; projected) and velocity (Δv <  300 km s−1) separations, and two additional faint narrow [CII]-emitting satellites. The overall system belongs to a larger scale protocluster environment and is coincident to one of its overdensity peaks. Additionally, ALMA reveals the presence of [CII] emission arising from a circumgalactic gas structure, extending up to a diameter-scale of ∼30 kpc. Our morpho-spectral decomposition analysis shows that about 50% of the total flux resides between the individual galaxy components, in a metal-enriched gaseous envelope characterised by a disturbed morphology and complex kinematics. Similarly to observations of shock-excited [CII] emitted from tidal tails in local groups, our results can be interpreted as a possible signature of interstellar gas stripped by strong gravitational interactions, with a possible contribution from material ejected by galactic outflows and emission triggered by star formation in small faint satellites. Our findings suggest that mergers could be an efficient mechanism of gas mixing in the circumgalactic medium around high-z galaxies, and thus play a key role in the galaxy baryon cycle at early epochs.

scholarly journals Chemical enrichment from massive stars in starbursts

1999 ◽  
Vol 193 ◽  
pp. 670-678 ◽  
Author(s):  
Henry A. Kobulnicky
Keyword(s):  
Ad Hoc ◽  
Massive Stars ◽  
Spatial Scales ◽  
Young Star ◽  
Fine Tuning ◽  
H Ii Regions ◽  
Chemical Homogeneity ◽  
Star Forming ◽  
Chemical Enrichment ◽  
The Galaxy

The warm ionized gas in low-mass, metal-poor star forming galaxies is chemically homogeneous despite the prevalence of large H II regions which contain hundreds of evolved massive stars, supernovae, and Wolf-Rayet stars with chemically-enriched winds. Galaxies with large WR star content are chemically indistinguishable from other vigorously star-forming galaxies. Furthermore, no significant localized chemical fluctuations are present in the vicinity of young star clusters, despite large expected chemical yields of massive stars. An ad hoc fine-tuning of the release, dispersal and mixing of the massive star ejecta could give rise to the observed homogeneity, but a more probable explanation is that fresh ejecta from massive stars reside in a hard-to-observe hot or cold phase. In any case, the observed chemical homogeneity indicates that heavy elements which have already mixed with the warm interstellar medium (thus accessible to optical spectroscopy) are homogeneously dispersed over scales exceeding 1 kpc. Mixing of fresh ejecta with the surrounding warm ISM apparently requires longer than the lifetimes of typical H II regions (> 107 yr). The lack of observed localized chemical enrichments is consistent with a scenario whereby freshly-synthesized metals from massive stars are expelled into the halos of galaxies in a hot, 106 K phase by supernova-driven winds before they cool and ‘rain’ back down upon the galaxy, creating gradual enrichments on spatial scales >1 kpc.

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