scholarly journals Exploring the Dust Content of Galactic Halos with Herschel*. III. NGC 891

2020 ◽  
Author(s):  
J H Yoon ◽  
C L Martin ◽  
S Veilleux ◽  
M Meléndez ◽  
T Mueller ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Thermal Emission ◽  
Formation Rate ◽  
Critical Role ◽  
Cosmic Ray ◽  
Far Infrared ◽  
Starburst Galaxy ◽  
Galactic Halos ◽  
Infrared Observations

Abstract We present deep far-infrared observations of the nearby edge-on galaxy NGC 891 obtained with the Herschel Space Observatory and the Spitzer Space Telescope. The maps confirm the detection of thermal emission from the inner circumgalactic medium (halo) and spatially resolve a dusty superbubble and a dust spur (filament). The dust temperature of the halo component is lower than that of the disk but increases across a region of diameter ≈8.0 kpc extending at least 7.7 kpc vertically from one side of the disk, a region we call a superbubble because of its association with thermal X-ray emission and a minimum in the synchrotron scaleheight. This outflow is breaking through the thick disk and developing into a galactic wind, which is of particular interest because NGC 891 is not considered a starburst galaxy; the star formation rate surface density, 0.03M⊙ yr−1 kpc−2, and gas fraction, just $10\%$ in the inner disk, indicate the threshold for wind formation is lower than previous work has suggested. We conclude that the star formation surface density is sufficient for superbubble blowout into the halo, but the cosmic ray electrons may play a critical role in determining whether this outflow develops into a fountain or escapes from the gravitational potential. The high dust-to-gas ratio in the dust spur suggests the material was pulled out of NGC 891 through the collision of a minihalo with the disk of NGC 891. We conclude that NGC 891 offers an example of both feedback and satellite interactions transporting dust into the halo of a typical galaxy.

scholarly journals Cosmic rays and non-thermal emission in simulated galaxies: III. probing cosmic ray calorimetry with radio spectra and the FIR-radio correlation

2021 ◽  
Author(s):  
Maria Werhahn ◽  
Christoph Pfrommer ◽  
Philipp Girichidis
Keyword(s):  
Steady State ◽  
Star Formation ◽  
Thermal Emission ◽  
High Redshift ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Far Infrared ◽  
Secondary Emission ◽  
Synchrotron Emission ◽  
Halo Masses

Abstract An extinction-free estimator of the star-formation rate (SFR) of galaxies is critical for understanding the high-redshift universe. To this end, the nearly linear, tight correlation of far-infrared (FIR) and radio luminosity of star-forming galaxies is widely used. While the FIR is linked to massive star formation, which also generates shock-accelerated cosmic ray (CR) electrons and radio synchrotron emission, a detailed understanding of the underlying physics is still lacking. Hence, we perform three-dimensional magneto-hydrodynamical (MHD) simulations of isolated galaxies over a broad range of halo masses and SFRs using the moving-mesh code Arepo, and evolve the CR proton energy density self-consistently. In post-processing, we calculate the steady-state spectra of primary, shock-accelerated and secondary CR electrons, which result from hadronic CR proton interactions with the interstellar medium. The resulting total radio luminosities correlate with the FIR luminosities as observed and are dominated by primary CR electrons if we account for anisotropic CR diffusion. The increasing contribution of secondary emission up to 30 per cent in starbursts is compensated by the larger bremsstrahlung and Coulomb losses. CR electrons are in the calorimetric limit and lose most of their energy through inverse Compton interactions with star-light and cosmic microwave background (CMB) photons while less energy is converted to synchrotron emission. This implies steep steady-state synchrotron spectra in starbursts. Interestingly, we find that thermal free–free emission flattens the total radio spectra at high radio frequencies and reconciles calorimetric theory with observations while free–free absorption explains the observed low-frequency flattening towards the central regions of starbursts.

scholarly journals CHANG-ES

2018 ◽  
Vol 611 ◽  
pp. A72 ◽  
Author(s):  
Marita Krause ◽  
Judith Irwin ◽  
Theresa Wiegert ◽  
Arpad Miskolczi ◽  
Ancor Damas-Segovia ◽  
...  
Keyword(s):  
Star Formation ◽  
Wind Velocity ◽  
Surface Density ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Scale Height ◽  
Radio Continuum ◽  
Frequency Bands

Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution.Methods. We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands.Results. The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, we defined a normalized scale height h˜ which is quite similar for all sample galaxies at both frequency bands and does not depend on the star formation rate or the magnetic field strength. However, h˜ shows a tight anticorrelation with the mass surface density.Conclusions. The sample galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter. The radio scale height depends mainly on the radio diameter of the galaxy. The sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies. While a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational evidence of a gravitational deceleration of CRE outflow, e.g. a lowering of the wind velocity from the galactic disk.

scholarly journals Cosmic rays across the star-forming galaxy sequence – I. Cosmic ray pressures and calorimetry

2021 ◽  
Vol 502 (1) ◽  
pp. 1312-1333
Author(s):  
Roland M Crocker ◽  
Mark R Krumholz ◽  
Todd A Thompson
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Surface Density ◽  
Large Scale ◽  
Gamma Ray ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Gas Content ◽  
Critical Surface ◽  
Pressure Balance

ABSTRACT In the Milky Way (MW), cosmic rays (CRs) are dynamically important in the interstellar medium (ISM), contribute to hydrostatic balance, and may help regulate star formation. However, we know far less about the importance of CRs in galaxies whose gas content or star formation rate (SFR) differ significantly from those of the MW. Here, we construct self-consistent models for hadronic CR transport, losses, and contribution to pressure balance as a function of galaxy properties, covering a broad range of parameters from dwarfs to extreme starbursts. While the CR energy density increases from ∼1 eV cm−3 to ∼1 keV cm−3 over the range from sub-MW dwarfs to bright starbursts, strong hadronic losses render CRs increasingly unimportant dynamically as the SFR surface density increases. In MW-like systems, CR pressure is typically comparable to turbulent gas and magnetic pressure at the galactic mid-plane, but the ratio of CR to gas pressure drops to ∼10−3 in dense starbursts. Galaxies also become increasingly CR calorimetric and gamma-ray bright in this limit. The degree of calorimetry at fixed galaxy properties is sensitive to the assumed model for CR transport, and in particular to the time CRs spend interacting with neutral ISM, where they undergo strong streaming losses. We also find that in some regimes of parameter space hydrostatic equilibrium discs cannot exist, and in Paper II of this series we use this result to derive a critical surface in the plane of star formation surface density and gas surface density beyond which CRs may drive large-scale galactic winds.

scholarly journals Search for Hα Emitters at z ∼ 7.8: A Constraint on the Hα-based Star Formation Rate Density

2022 ◽  
Vol 924 (2) ◽  
pp. 71
Author(s):  
Yoshihisa Asada ◽  
Kouji Ohta
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Far Infrared ◽  
Infrared Observations ◽  
Upper Limit ◽  
Star Formation Activity

Abstract We search for Hα emitters at z ∼ 7.8 in four gravitationally lensed fields observed in the Hubble Frontier Fields program. We use the Lyman break method to select galaxies at the target redshift and perform photometry in the Spitzer/IRAC 5.8 μm band to detect Hα emission from the candidate galaxies. We find no significant detections of counterparts in the IRAC 5.8 μm band, and this gives a constraint on the Hα luminosity function (LF) at z ∼ 7.8. We compare the constraint with previous studies based on rest-frame UV and far-infrared observations using the correlation between the Hα luminosity and the star formation rate. Additionally, we convert the constraint on the Hα LF into an upper limit for the star formation rate density (SFRD) at this epoch assuming the shape of the LF. We examine two types of parameterization of the LF and obtain an upper limit for the SFRD of log 10 ( ρ SFR [ M ⊙ yr − 1 Mpc − 3 ] ) ≲ − 1.1 at z ∼ 7.8. With this constraint on the SFRD, we present an independent probe into the total star formation activity including dust-obscured and unobscured star formation at the Epoch of Reionization.

scholarly journals Far-infrared star formation rates of six GRB host galaxies with ALMA

2020 ◽  
Vol 496 (4) ◽  
pp. 4405-4419
Author(s):  
Tiger Yu-Yang Hsiao ◽  
Tetsuya Hashimoto ◽  
Jia-Yuan Chang ◽  
Tomotsugu Goto ◽  
Seong Jin Kim ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Far Infrared ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Host Galaxies ◽  
Distribution Fitting

ABSTRACT Gamma-ray bursts (GRBs) can be a promising tracer of cosmic star formation rate history (CSFRH). In order to reveal the CSFRH using GRBs, it is important to understand whether they are biased tracers or not. For this purpose, it is crucial to understand properties of GRB host galaxies, in comparison to field galaxies. In this work, we report ALMA far-infrared (FIR) observations of six z ∼ 2 IR-bright GRB host galaxies, which are selected for the brightness in IR. Among them, four host galaxies are detected for the first time in the rest-frame FIR. In addition to the ALMA data, we collected multiwavelength data from previous studies for the six GRB host galaxies. Spectral energy distribution fitting analyses were performed with cigale to investigate physical properties of the host galaxies, and to test whether active galactic nucleus (AGN) and radio components are required or not. Our results indicate that the best-fitting templates of five GRB host galaxies do not require an AGN component, suggesting the absence of AGNs. One GRB host galaxy, 080207, shows a very small AGN contribution. While derived stellar masses of the three host galaxies are mostly consistent with those in previous studies, interestingly the value of star formation rates (SFRs) of all six GRB hosts are inconsistent with previous studies. Our results indicate the importance of rest-frame FIR observations to correctly estimate SFRs by covering thermal emission from cold dust heated by star formation.

scholarly journals Cosmic rays across the star-forming galaxy sequence. II: Stability limits and the onset of cosmic ray-driven outflows

2021 ◽  
Author(s):  
Roland M Crocker ◽  
Mark R Krumholz ◽  
Todd A Thompson
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Surface Density ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Star Forming ◽  
Rate Versus ◽  
The Galaxy ◽  
Plausible Mechanism

Abstract Cosmic rays (CRs) are a plausible mechanism for launching winds of cool material from the discs of star-forming galaxies. However, there is no consensus on what types of galaxies likely host CR-driven winds, or what role these winds might play in regulating galaxies’ star formation rates. Using a detailed treatment of the transport and losses of hadronic CRs developed in the previous paper in this series, here we develop a semi-analytic model that allows us to assess the viability of using CRs to launch cool winds from galactic discs. In particular, we determine the critical CR fluxes – and corresponding star formation rate surface densities – above which hydrostatic equilibrium within a given galaxy is precluded because CRs drive the gas off in a wind or otherwise render it unstable. Our model demonstrates that catastrophic, CR-driven wind loss is a possibility at galactic mean surface densities below $\, {\lesssim}\, 10^2 \ M_{\odot }$ pc−2. In this regime – encompassing the Galaxy and local dwarfs – the locus of the CR stability curve patrols the high side of the observed distribution of galaxies in the Kennicutt-Schmidt parameter space of star formation rate versus gas surface density. However, hadronic losses render CRs unable to drive global winds in galaxies with surface densities above the ∼102 − 103M⊙ pc−2 transition region. Our results show that quiescent, low surface density galaxies like the Milky Way are poised on the cusp of instability, such that small changes to ISM parameters can lead to the launching of CR-driven outflows, and we suggest that, as a result, CR feedback sets an ultimate limit to the star formation efficiency of most modern galaxies.

scholarly journals Gas, dust, and star formation in the positive AGN feedback candidate 4C 41.17 at z = 3.8

2020 ◽  
Vol 639 ◽  
pp. L13
Author(s):  
N. P. H. Nesvadba ◽  
G. V. Bicknell ◽  
D. Mukherjee ◽  
A. Y. Wagner
Keyword(s):  
Star Formation ◽  
Positive Feedback ◽  
Surface Density ◽  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Far Infrared ◽  
Star Forming ◽  
Radio Jets ◽  
Narrow Ridge

We present new, spatially resolved [CI]1–0, [CI]2–1, CO(7–6), and dust continuum observations of 4C 41.17 at z = 3.8. This is one of the best-studied radio galaxies in this epoch and is arguably the best candidate of jet-triggered star formation at high redshift currently known in the literature. 4C 41.17 shows a narrow ridge of dust continuum extending over 15 kpc near the radio jet axis. Line emission is found within the galaxy in the region with signatures of positive feedback. Using the [CI]1–0 line as a molecular gas tracer, and multifrequency observations of the far-infrared dust heated by star formation, we find a total gas mass of 7.6 × 1010 M⊙, which is somewhat greater than that previously found from CO(4–3). The gas mass surface density of 103 M⊙ yr−1 pc−2 and the star formation rate surface density of 10 M⊙ yr−1 kpc−2 were derived over the 12 kpc × 8 kpc area, where signatures of positive feedback have previously been found. These densities are comparable to those in other populations of massive, dusty star-forming galaxies in this redshift range, suggesting that the jet does not currently enhance the efficiency with which stars form from the gas. This is consistent with expectations from simulations, whereby radio jets may facilitate the onset of star formation in galaxies without boosting its efficiency over longer timescales, in particular after the jet has broken out of the interstellar medium, as is the case in 4C 41.17.

scholarly journals Testing the star formation scaling relations in the clumps of the North American and Pelican nebulae cloud complex

2020 ◽  
Vol 500 (3) ◽  
pp. 3123-3141
Author(s):  
Swagat R Das ◽  
Jessy Jose ◽  
Manash R Samal ◽  
Shaobo Zhang ◽  
Neelam Panwar
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Free Fall ◽  
Scaling Relations ◽  
Time Model ◽  
Fall Time ◽  
The North ◽  
Crossing Time

ABSTRACT The processes that regulate star formation within molecular clouds are still not well understood. Various star formation scaling relations have been proposed as an explanation, one of which is to formulate a relation between the star formation rate surface density $\rm \Sigma _{SFR}$ and the underlying gas surface density $\rm \Sigma _{gas}$. In this work, we test various star formation scaling relations, such as the Kennicutt–Schmidt relation, the volumetric star formation relation, the orbital time model, the crossing time model and the multi free-fall time-scale model, towards the North American Nebula and Pelican Nebula and in the cold clumps associated with them. Measuring stellar mass from young stellar objects and gaseous mass from CO measurements, we estimate the mean $\rm \Sigma _{SFR}$, the star formation rate per free-fall time and the star formation efficiency for clumps to be 1.5 $\rm M_{\odot}\, yr^{-1}\, kpc^{-2}$, 0.009 and 2.0 per cent, respectively, while for the whole region covered by both nebulae (which we call the ‘NAN’ complex) the values are 0.6 $\rm M_{\odot}\, yr^{-1}\, kpc^{-2}$, 0.0003 and 1.6 per cent, respectively. For the clumps, we notice that the observed properties are in line with the correlation obtained between $\rm \Sigma _{SFR}$ and $\rm \Sigma _{gas}$, and between $\rm \Sigma _{SFR}$ and $\rm \Sigma _{gas}$ per free-fall time and orbital time for Galactic clouds. At the same time, we do not observe any correlation with $\rm \Sigma _{gas}$ per crossing time and multi free-fall time. Even though we see correlations in the former cases, however, all models agree with each other within a factor of 0.5 dex. It is not possible to discriminate between these models because of the current uncertainties in the input observables. We also test the variation of $\rm \Sigma _{SFR}$ with the dense gas but, because of low statistics, a weak correlation is seen in our analysis.

scholarly journals Far-Infrared Emission from Clumpy Irregular Galaxies

1987 ◽  
Vol 115 ◽  
pp. 647-647
Author(s):  
U. Klein ◽  
J. Heidmann ◽  
R. Wielebinski ◽  
E. Wunderlich
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Hubble Constant ◽  
Far Infrared ◽  
Hii Regions ◽  
Infrared Emission ◽  
Star Forming ◽  
Irregular Galaxies

The four clumpy irregular galaxies Mkr 8, 296,297 and 325 have been observed by IRAS. All galaxies have been detected in at least two of the four detector bands. The ratios of the 100 to 60-m flux densities are comparable to those of HII regions or violently star forming galaxies. The average star formation rate in clumpy irregular galaxies is of the order of a few solar masses per year (based on their average far-infrared luminosity and a Hubble constant of 75 km s−1 Mpc−1.

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