scholarly journals A cautionary tale of attenuation in star-forming regions

2020 ◽  
Vol 494 (4) ◽  
pp. 4751-4770 ◽  
Author(s):  
Mallory Molina ◽  
Nikhil Ajgaonkar ◽  
Renbin Yan ◽  
Robin Ciardullo ◽  
Caryl Gronwall ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dust Content ◽  
Physical Parameters ◽  
Star Forming ◽  
Total Dust ◽  
Star Forming Regions ◽  
Field Unit

ABSTRACT The attenuation of light from star-forming galaxies is correlated with a multitude of physical parameters including star formation rate, metallicity and total dust content. This variation in attenuation is even more evident on kiloparsec scales, which is the relevant size for many current spectroscopic integral field unit surveys. To understand the cause of this variation, we present and analyse Swift/UVOT near-UV (NUV) images and SDSS/MaNGA emission-line maps of 29 nearby (z < 0.084) star-forming galaxies. We resolve kiloparsec-sized star-forming regions within the galaxies and compare their optical nebular attenuation (i.e. the Balmer emission line optical depth, $\tau ^{l}_{B}\equiv \tau _{\textrm {H}\beta }-\tau _{\textrm {H}\alpha }$) and NUV stellar continuum attenuation (via the NUV power-law index, β) to the attenuation law described by Battisti et al. We show the data agree with that model, albeit with significant scatter. We explore the dependence of the scatter of the β–$\tau ^{l}_{B}$ measurements from the star-forming regions on different physical parameters, including distance from the nucleus, star formation rate and total dust content. Finally, we compare the measured $\tau ^{l}_{B}$ and β values for the individual star-forming regions with those of the integrated galaxy light. We find a strong variation in β between the kiloparsec scale and the larger galaxy scale that is not seen in $\tau ^{l}_{B}$. We conclude that the sightline dependence of UV attenuation and the reddening of β due to the light from older stellar populations could contribute to the scatter in the β–$\tau ^{l}_{B}$ relation.

scholarly journals Modes of star formation from Herschel

2012 ◽  
Vol 8 (S292) ◽  
pp. 87-90
Author(s):  
L. Testi ◽  
E. Bressert ◽  
S. Longmore
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
Dense Gas ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Massive Cluster

AbstractWe summarize some of the results obtained from Herschel surveys of nearby star forming regions and the Galactic plane. We show that in the nearby star forming regions the starless core spatial surface density distribution is very similar to that of the young stellar objects. This, taken together with the similarity between the core mass function and the initial mass function for stars and the relationship between the amount of dense gas and star formation rate, suggest that the cloud fragmentation process defines the global outcome of star formation. This “simple” view of star formation may not hold on all scales. In particular dynamical interactions are expected to become important at the conditions required to form young massive clusters. We describe the successes of a simple criterion to identify young massive cluster precursors in our Galaxy based on (sub-)millimeter wide area surveys. We further show that in the location of our Galaxy where the best candidate for a precursor of a young massive cluster is found, the “simple” scaling relationship between dense gas and star formation rate appear to break down. We suggest that in regions where the conditions approach those of the central molecular zone of our Galaxy it may be necessary to revise the scaling laws for star formation.

scholarly journals Theory of the Star Formation Rate

2010 ◽  
Vol 6 (S270) ◽  
pp. 347-354
Author(s):  
Paolo Padoan ◽  
Åke Nordlund
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Large Set ◽  
Relative Importance ◽  
Transient Phase ◽  
Mhd Turbulence ◽  
Star Forming ◽  
Star Forming Regions ◽  
Theoretical Predictions

AbstractThis work presents a new physical model of the star formation rate (SFR), tested with a large set of numerical simulations of driven, supersonic, self-gravitating, magneto-hydrodynamic (MHD) turbulence, where collapsing cores are captured with accreting sink particles. The model depends on the relative importance of gravitational, turbulent, magnetic, and thermal energies, expressed through the virial parameter, αvir, the rms sonic Mach number, S,0, and the ratio of mean gas pressure to mean magnetic pressure, β0. The SFR is predicted to decrease with increasing αvir (stronger turbulence relative to gravity), and to depend weakly on S,0 and β0, for values typical of star forming regions (S,0≈4-20 and β0≈1-20). The star-formation simulations used to test the model result in an approximately constant SFR, after an initial transient phase. Both the value of the SFR and its dependence on the virial parameter found in the simulations agree very well with the theoretical predictions.

scholarly journals Toward unveiling internal properties of Hii regions and their connections at the cosmic noon era

2015 ◽  
Vol 11 (S319) ◽  
pp. 53-53
Author(s):  
Rhythm Shimakawa ◽  
Tadayuki Kodama ◽  
Masao Hayashi ◽  
Ken-ichi Tadaki ◽  
Tomoko L. Suzuki ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Formation Rate ◽  
Physical Parameters ◽  
Star Forming ◽  
Radiation Fields ◽  
Star Forming Regions ◽  
Physical Scale ◽  
High Level

AbstractThe redshift interval z = 2–3 is known as the cosmic noon that is the most active era of star formation across the Universe (Hopkins & Beacom 2006). In the past decade, many authors have investigated global properties of star-forming (SF) galaxies in this turbulent era, such as gas fractions and gaseous metallicities (e.g. Erb et al. 2006). With those achievements, we are going on to the next stage to understand more details i.e. those physical parameters in star-forming regions. Recent advent of near-infrared instruments typified by MOSFIRE on the Keck telescope, enable us with identifying the physical parameters of Hii regions in ‘typical’ SF galaxies individually (Steidel et al. 2014). Recent highlights suggest higher electron densities, higher ionization parameters, and harder UV radiation fields may be common.In order to know how galaxy evolution physically correlates with the natures of their star-forming regions, we have explored relationships between the electron density (ne) of ionized gas from the oxygen line ratio and other physical properties, based on the deep spectra of Hα emitters at z = 2.5 by the MOSFIRE. MOSFIRE for the first time provides ne of the galaxies at high-z with a high level of confidence. The result shows the specific star formation rate (sSFR) and the SFR surface density (ΣSFR) are correlated with ne (Shimakawa et al. 2015). The ne-ΣSFR relation could be linked to the star formation law in Hii regions if we assume that hydrogen in Hii regions is fully-ionized. Otherwise, more active star formation per unit area (higher ΣSFRs), may cause higher ionization states. However, we need some specific concerns that obtained physical parameters should depend on the scale dependence, since typical size of Hii region is only <100 pc despite that we study physical states of entire galaxies. Thus we obtain surface-brightness-weighted and ensemble averaged line fluxes for the entire galaxy or the part that falls into the slit width (a few kpc scale size). The thirty meter telescope (TMT) is a powerful instrument to resolve such a difficulty, since its spatial resolution reaches <100 pc on the physical scale at z ~ 2 by AO assistance.

scholarly journals The evolution of the equivalent width of the Hα emission line and specific star formation rate in star-forming galaxies at 1 < z < 5

2016 ◽  
Vol 460 (4) ◽  
pp. 3587-3597 ◽  
Author(s):  
E. Mármol-Queraltó ◽  
R. J. McLure ◽  
F. Cullen ◽  
J. S. Dunlop ◽  
A. Fontana ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Equivalent Width ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Forming ◽  
Hα Emission

scholarly journals Star Formation in the Local Milky Way

2015 ◽  
Vol 10 (S314) ◽  
pp. 8-15
Author(s):  
Charles J. Lada
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Young Stars ◽  
Molecular Gas ◽  
Physical Processes ◽  
Star Forming ◽  
Star Forming Regions

AbstractStudies of molecular clouds and young stars near the sun have provided invaluable insights into the process of star formation. Indeed, much of our physical understanding of this topic has been derived from such studies. Perhaps the two most fundamental problems confronting star formation research today are: 1) determining the origin of stellar mass and 2) deciphering the nature of the physical processes that control the star formation rate in molecular gas. As I will briefly outline here, observations and studies of local star forming regions are making particularly significant contributions toward the solution of both these important problems.

scholarly journals J-PLUS: Measuring Hα emission line fluxes in the nearby universe

2019 ◽  
Vol 622 ◽  
pp. A180 ◽  
Author(s):  
R. Logroño-García ◽  
G. Vilella-Rojo ◽  
C. López-Sanjuan ◽  
J. Varela ◽  
K. Viironen ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Narrow Band ◽  
Formation Rate ◽  
Photometric Data ◽  
Star Forming ◽  
Spatially Resolved ◽  
Band Filter ◽  
Narrow Band Filter

In this paper we aim to validate a methodology designed to obtain Hα emission line fluxes from J-PLUS photometric data. J-PLUS is a multi narrow-band filter survey carried out with the 2 deg2 field of view T80Cam camera, mounted on the JAST/T80 telescope in the OAJ, Teruel, Spain. The information of the twelve J-PLUS bands, including the J0660 narrow-band filter located at rest-frame Hα, is used over the first 42 deg2 observed to retrieve de-reddened and [NII] decontaminated Hα emission line fluxes of 46 star-forming regions with previous SDSS and/or CALIFA spectroscopic information. The agreement between the J-PLUS Hα fluxes and those obtained with spectroscopic data is remarkable, finding a median comparison ratio with a scatter of $ \mathcal{R}\,{=}\,F^{\mathrm{J-PLUS}}_{\mathrm{H\alpha}}/F^{\mathrm{spec}}_{\mathrm{H\alpha}}\,{=}\,1.05\,{\pm}\,0.25 $. This demonstrates that it is possible to retrieve reliable Hα emission line fluxes from J-PLUS photometric data. With an expected area of thousands of square degrees upon completion, the J-PLUS dataset will allow the study of several star formation science cases in the nearby universe, as the spatially resolved star formation rate of nearby galaxies at z  ≤  0.015, and how it is influenced by the environment, morphology, stellar mass, and nuclear activity. As an illustrative example, the close pair of interacting galaxies NGC 3994 and NGC 3995 is analysed, finding an enhancement of the star formation rate not only in the centre, but also in outer parts of the disk of NGC 3994.

scholarly journals The dense galactic environments of the Milky Way

2018 ◽  
Vol 14 (S345) ◽  
pp. 34-38
Author(s):  
Quang Nguyen-Luong ◽  
Neal Evans ◽  
Kee-Tae Kim ◽  
Hyunwoo Kang ◽  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Rate Relation

AbstractStar formation takes place in the dense gas phase, and therefore a simple dense gas and star formation rate relation has been proposed. With the advent of multi-beam receivers, new observations show that the deviation from linear relations is possible. In addition, different dense gas tracers might also change significantly the measurement of dense gas mass and subsequently the relation between star formation rate and dense gas mass. We report the preliminary results the DEnse GAs in MAssive star-forming regions in the Milky Way (DEGAMA) survey that observed the dense gas toward a suite of well-characterized massive star-forming regions in the Milky Way. Using the resulting maps of HCO+ 1–0, HCN 1–0, CS 2–1, we discuss the current understanding of the dense gas phase where star formation takes place.

scholarly journals Gemini IFU, VLA, and HST observations of the OH Megamaser Galaxy IRAS17526 + 3253★

2019 ◽  
Vol 486 (3) ◽  
pp. 3350-3367 ◽  
Author(s):  
Dinalva A Sales ◽  
A Robinson ◽  
R A Riffel ◽  
T Storchi-Bergmann ◽  
J F Gallimore ◽  
...  
Keyword(s):  
Star Formation ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Line Emission ◽  
Ionization Source ◽  
Space Telescope ◽  
Star Forming ◽  
Star Forming Regions ◽  
Major Merger ◽  
Field Unit

AbstractWe present a multiwavelength study of the OH megamaser galaxy IRAS17526 + 3253, based on new Gemini multi-object spectrograph integral field unit (GMOS/IFU) observations, Hubble Space Telescope F814W, and H α + [N ii] images, and archival 2MASS and 1.49 GHz VLA data. The Hubble Space Telescope(HST) images clearly reveal a mid-to-advanced stage major merger whose northwestern and southeastern nuclei have a projected separation of ∼8.5 kpc. Our HST/H α + [N ii] image shows regions of ongoing star formation across the envelope on ∼10 kpc scales, which are aligned with radio features, supporting the interpretation that the radio emission originates from star-forming regions. The measured H α luminosities imply that the unobscured star formation rate (SFR) is ∼10–30 M⊙ yr−1. The GMOS/IFU data reveal two structures in northwestern separated by 850 pc and by a discontinuity in the velocity field of ∼ 200 km s−1. We associate the blueshifted and redshifted components with, respectively, the distorted disc of northwestern and tidal debris, possibly a tail originating in southeastern. Star formation is the main ionization source in both components, which have SFRs of ∼2.6–7.9 M⊙ yr−1 and ∼1.5–4.5 M⊙ yr−1, respectively. Fainter line emission bordering these main components is consistent with shock ionization at a velocity ∼200 km s−1 and may be the result of an interaction between the tidal tail and the northwestern galaxy’s disc. IRAS17526 + 3253 is one of only a few systems known to host both luminous OH and H2O masers. The velocities of the OH and H2O maser lines suggest that they are associated with the northwestern and southeastern galaxies, respectively (Martin et al.; Wagner).

scholarly journals Molecular Gas and Star Formation in the NGC 3077 Tidal Arm

2004 ◽  
Vol 217 ◽  
pp. 498-503 ◽  
Author(s):  
Fabian Walter ◽  
Crystal Martin ◽  
Jürgen Ott ◽  
Andreas Heithausen
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Compact Star ◽  
Formation Rate ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Interacting Systems ◽  
The Given ◽  
Hubble Time

We report the discovery of extended star formation in the prominent tidal arms near NGC 3077 (member of the M 81 triplet). 36 faint compact star forming regions were identified, covering an area of 4 × 6 kpc2. HII regions are only found near the southern rim of the tidal HI arm where the HI column density reaches values above 1 × 1021 cm−2. This threshold is very similar to what is found in ‘normal’ galactic environments. We derive a total star formation rate of 2.6 × 10−3M⊙ yr−1 in the tidal feature. We also present the first high-resolution observations of molecular gas in this region. The molecular gas emission can be separated into at least 5 distinct complexes most of which do not coincide with sites of star formation. The reservoir of neutral and molecular gas in the tidal arm is huge (~5 × 108M⊙); star formation may continue at the given rate for a Hubble time. We conclude that wide-spread low-level star formation may be a common phenomenon in tidal HI tails, however it will be difficult to detect in interacting systems that are further away.

scholarly journals What drives galaxy quenching? Resolving molecular gas and star formation in the green valley

2020 ◽  
Vol 498 (1) ◽  
pp. L66-L71 ◽  
Author(s):  
Simcha Brownson ◽  
Francesco Belfiore ◽  
Roberto Maiolino ◽  
Lihwai Lin ◽  
Stefano Carniani
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Gas Content ◽  
Molecular Gas ◽  
Data Sets ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Central Regions

ABSTRACT We study quenching in seven green valley galaxies on kpc scales by resolving their molecular gas content using 12CO(1–0) observations obtained with NOrthern Extended Millimeter Array and Atacama Large Millimeter Array, and their star formation rate using spatially resolved optical spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory survey. We perform radial stacking of both data sets to increase the sensitivity to molecular gas and star formation, thereby avoiding biases against strongly quenched regions. We find that both spatially resolved gas fraction (fgas) and star formation efficiency ($\rm {SFE}$) are responsible for quenching green valley galaxies at all radii: both quantities are suppressed with respect to typical star-forming regions. fgas and $\rm {SFE}$ have roughly equal influence in quenching the outer disc. We are, however, unable to identify the dominant mechanism in the strongly quenched central regions. We find that fgas is reduced by $\rm \sim\! 1~dex$ in the central regions, but the star formation rate is too low to be measured, leading to upper limits for the $\rm {SFE}$. Moving from the outer disc to central regions, the reduction in fgas is driven by an increasing $\rm \Sigma _{\star }$ profile rather than a decreasing $\rm \Sigma _{H_{2}}$ profile. The reduced fgas may therefore be caused by a decrease in the gas supply rather than molecular gas ejection mechanisms, such as winds driven by active galactic nuclei. We warn more generally that studies investigating fgas may be deceiving in inferring the cause of quenching, particularly in the central (bulge-dominated) regions of galaxies.

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