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 The global star formation law by supernova feedback

2019 ◽  
Vol 488 (4) ◽  
pp. 4753-4778 ◽  
Author(s):  
Avishai Dekel ◽  
Kartick C Sarkar ◽  
Fangzhou Jiang ◽  
Frederic Bournaud ◽  
Mark R Krumholz ◽  
...  
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Filling Factor ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Self Regulation ◽  
Free Fall ◽  
The Self ◽  
Fall Time ◽  
Supernova Feedback

ABSTRACT We address a simple model where the Kennicutt–Schmidt (KS) relation between the macroscopic densities of star formation rate (SFR, ρsfr) and gas (n) in galactic discs emerges from self-regulation of the SFR via supernova feedback. It arises from the physics of supernova bubbles, insensitive to the microscopic SFR recipe and not explicitly dependent on gravity. The key is that the filling factor of SFR-suppressed supernova bubbles self-regulates to a constant, f ∼ 0.5. Expressing the bubble fading radius and time in terms of n, the filling factor is $f\propto S\, n^{-s}$ with s ≃ 1.5, where S is the supernova rate density. A constant f thus refers to ρsfr ∝ n1.5, with a density-independent SFR efficiency per free-fall time ∼0.01. The self-regulation to f ∼ 0.5 and the convergence to a KS relation independent of the local SFR recipe are demonstrated in cosmological and isolated-galaxy simulations using different codes and recipes. In parallel, the spherical analysis of bubble evolution is generalized to clustered supernovae, analytically and via simulations, yielding s ≃ 1.5 ± 0.5. An analysis of photoionized bubbles about pre-supernova stars yields a range of KS slopes but the KS relation is dominated by the supernova bubbles. Superbubble blowouts may lead to an alternative self-regulation by outflows and recycling. While the model is oversimplified, its simplicity and validity in the simulations may argue that it captures the origin of the KS relation.

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 Efficacy of early stellar feedback in low gas surface density environments

2019 ◽  
Vol 491 (2) ◽  
pp. 2088-2103 ◽  
Author(s):  
Rahul Kannan ◽  
Federico Marinacci ◽  
Christine M Simpson ◽  
Simon C O Glover ◽  
Lars Hernquist
Keyword(s):  
Star Formation ◽  
Radiation Pressure ◽  
Surface Density ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Medium Density ◽  
Hydrodynamic Simulations ◽  
Radiative Feedback ◽  
Stellar Feedback ◽  
Radiation Feedback

ABSTRACT We present a suite of high-resolution radiation hydrodynamic simulations of a small patch (1 kpc2) of the interstellar medium (ISM) performed with arepo-rt, with the aim to quantify the efficacy of various feedback processes like supernova (SN) explosions, photoheating, and radiation pressure in low gas surface density galaxies (Σgas ≃ 10 M⊙ pc−2). We show that radiative feedback decrease the star formation rate and therefore the total stellar mass formed by a factor of approximately two. This increases the gas depletion time-scale and brings the simulated Kennicutt–Schmidt relation closer to the observational estimates. Radiation feedback coupled with SN is more efficient at driving outflows with the mass and energy loading increasing by a factor of ∼10. This increase is mainly driven by the additional entrainment of medium-density (10−2  cm−3 ≤ n < 1 cm−3) warm (300 K ≤ T < 8000 K) material. Therefore, including radiative feedback tends to launch colder, denser, and more mass- and energy-loaded outflows. This is because photoheating of the high-density gas around a newly formed star overpressurizes the region, causing it to expand. This reduces the ambient density in which the SN explode by a factor of 10–100 which in turn increases their momentum output by a factor of ∼1.5–2.5. Finally, we note that in these low gas surface density environments, radiative feedback primarily impact the ISM via photoheating and radiation pressure has only a minimal role in regulating star formation.

scholarly journals The evolution of the spiral galaxy M51a

2015 ◽  
Vol 11 (S319) ◽  
pp. 129-129
Author(s):  
Xiaoyu Kang ◽  
Fenghui Zhang ◽  
Ruixiang Chang
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Evolutionary History ◽  
Surface Brightness ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Molecular Gas ◽  
Peak Time ◽  
Model Predictions ◽  
Inside Out

AbstractA simple model for M51a is constructed to explore its evolutionary history by assuming its disk grows from continuous gas infall, which is shaped by a free parameter-the infall-peak time tp. By adopting a constant infall-peak time tp = 7.0Gyr, our model predictions can reproduce most of the observed constraints and still show that the disk of M51a forms inside-out. Our results also show that the current molecular gas surface density, the star-formation rate and the UV-band surface brightness are important quantities to trace the effect of recent interactions on galactic star-formation process.

scholarly journals Is this an early stage merger? A case study on molecular gas and star formation properties of Arp 240

2020 ◽  
Vol 496 (4) ◽  
pp. 5243-5261 ◽  
Author(s):  
Hao He ◽  
C D Wilson ◽  
Kazimierz Sliwa ◽  
Daisuke Iono ◽  
Toshiki Saito
Keyword(s):  
Star Formation ◽  
Early Stage ◽  
Formation Rate ◽  
Free Fall ◽  
Radio Continuum ◽  
Local Thermal Equilibrium ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Fall Time ◽  
Very Large Array

ABSTRACT We present new high-resolution 12CO J = 1–0, J = 2–1, and 13CO J = 1–0 maps of the early stage merger Arp 240 (NGC 5257/8) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Simulations in the literature suggest that the merger has just completed its first passage; however, we find that this system has a lower global gas fraction but a higher star formation efficiency (SFE) compared to typical close galaxy pairs, which suggests that this system may already be in an advanced merger stage. We combine the ALMA data with 12CO J = 3–2 observations from the Submillimeter Array and carry out RADEX modelling on several different regions. Both, the RADEX modelling and a local thermal equilibrium (LTE) analysis show that the regions are most likely to have a CO-to-H2 conversion factor αCO close to or perhaps even smaller than the typical value for (ultra)luminous infrared galaxies. Using 33-GHz data from the Very Large Array to measure the star formation rate, we find that most star-forming regions have molecular gas depletion times of less than 100 Myr. We calculated the SFE per free-fall time for different regions and find some regions appear to have values greater than 100 per cent. We find these regions generally show evidence for young massive clusters (YMCs). After exploring various factors, we argue that this is mainly due to the fact that radio continuum emission in those regions is dominated by that from YMCs, which results in an overestimate of the SFE per free-fall time.

scholarly journals Scaling relations of metallicity, stellar mass and star formation rate in metal-poor starbursts – I. A Fundamental Plane

2012 ◽  
Vol 427 (2) ◽  
pp. 906-918 ◽  
Author(s):  
Leslie Hunt ◽  
Laura Magrini ◽  
Daniele Galli ◽  
Raffaella Schneider ◽  
Simone Bianchi ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Stellar Mass ◽  
Scaling Relations ◽  
Fundamental Plane

scholarly journals Stellar Explosions in High-surface Density Galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 232-232
Author(s):  
Evan Scannapieco ◽  
Sharanya Sur ◽  
Eve C. Ostriker
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Energy Input ◽  
Large Scale ◽  
Star Formation Rate ◽  
High Surface ◽  
Formation Rate ◽  
Three Dimensional ◽  
Velocity Dispersions ◽  
The Impact

AbstractHigh surface density, rapidly star-forming galaxies are observed to have ≈ 50 - 100 km s−1 line-of-sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae.We find that such motions lead to strong global outflows in the highly-compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent today. Substantial outflows are generated if the one-dimensional horizontal velocity dispersion exceeds -35 km s−1, as occurs in the dense disks that have star formation rate densities above ≈ 0.1 M⊙ yr−1 kpc−2. These outflows are triggered by a thermal runaway, arising from the inefficient cooling of hot material coupled with successive heating from turbulent driving. Thus, even in the absence of stellar feedback, a critical value of the star-formation rate density for outflow generation can arise due to a turbulent heating instability. This suggests that in strongly self-gravitating disks, outflows may be enhanced by, but need not caused by, energy input from stellar explosions.These results are explained in more detailed in Sur, Scannapieco, & Ostriker (2015).

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