scholarly journals A new estimator of resolved molecular gas in nearby galaxies

2020 ◽  
Vol 500 (1) ◽  
pp. 1261-1278
Author(s):  
Ryan Chown ◽  
Cheng Li ◽  
Laura Parker ◽  
Christine D Wilson ◽  
Niu Li ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Line Emission ◽  
Wide Field ◽  
Star Forming ◽  
Star Forming Regions ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
Multivariable Regression ◽  
Nearby Galaxies

ABSTRACT A relationship between dust-reprocessed light from recent star formation and the amount of star-forming gas in a galaxy produces a correlation between Wide-field Infrared Survey Explorer (WISE) 12 μm emission and CO line emission. Here, we explore this correlation on kiloparsec scales with CO(1–0) maps from EDGE–CALIFA matched in resolution to WISE 12 μm images. We find strong CO-12 μm correlations within each galaxy and we show that the scatter in the global CO-12 μm correlation is largely driven by differences from galaxy to galaxy. The correlation is stronger than that between star formation rate and H2 surface densities [Σ(H2)]. We explore multivariable regression to predict Σ(H2) in star-forming pixels using the WISE 12 μm data combined with global and resolved galaxy properties, and provide the fit parameters for the best estimators. We find that Σ(H2) estimators that include $\Sigma (\mathrm{12\:\mu m})$ are able to predict Σ(H2) more accurately than estimators that include resolved optical properties instead of $\Sigma (\mathrm{12\:\mu m})$. These results suggest that 12 μm emission and H2 as traced by CO emission are physically connected at kiloparsec scales. This may be due to a connection between polycyclic aromatic hydrocarbon emission and the presence of H2. The best single-property estimator is $\log \frac{\Sigma (\mathrm{H_2})}{\mathrm{M_\odot \:pc^{-2}}} = (0.48 \pm 0.01) + (0.71 \pm 0.01)\log \frac{\Sigma (\mathrm{12\:\mu m})}{\mathrm{L_\odot \:pc^{-2}}}$. This correlation can be used to efficiently estimate Σ(H2) down to at least 1 M⊙ pc−2 in star-forming regions within nearby galaxies.

scholarly journals Identification of extragalactic star forming complexes

2021 ◽  
Author(s):  
D. D. Lisitsin ◽  
◽  
A. V. Kuzin ◽  
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Young Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Spectral Bands ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
External Galaxies ◽  
Nearby Galaxies

We developed a technique for selecting star forming complexes in external galaxies based on an analysis of radiation maps in various spectral bands. Using this method, we identified star formation complex candidates in 17 nearby galaxies applying three criteria. These criteria are polycyclic aromatic hydrocarbon emission, dust emission, and ultraviolet young star emission. Relating the information derived from these criteria, we made a sample of star forming regions suitable for revealing correlations between various star formation tracers.

Star formation and polycyclic aromatic hydrocarbons in ELAIS N1 galaxies as seen by AKARI

2019 ◽  
Vol 71 (2) ◽  
Author(s):  
Tímea O Kovács ◽  
Denis Burgarella ◽  
Hidehiro Kaneda ◽  
Dániel Cs Molnár ◽  
Shinki Oyabu ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Star Formation ◽  
Aromatic Hydrocarbons ◽  
Main Sequence ◽  
Compact Star ◽  
Formation Rate ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Polycyclic Aromatic

Abstract We have examined the relationship between star formation and polycyclic aromatic hydrocarbons (PAHs) in a variety of galaxies. PAHs are excited by the ultraviolet photons of young stars, but they are disassociated by strong UV radiation in starbursts. Therefore their emission (which is in the wavelength range covered by AKARI) can be used as a star formation tracer in main sequence galaxies. We selected our targets in the ELAIS N1 field with AKARI detections, matched them with the Herschel Point Source Catalog, and collected other publicly available photometric data. Their spectral energy distributions (SEDs) were fitted, and several parameters of the galaxies were estimated, e.g., star formation rate (SFR), stellar mass, and the fraction of PAHs compared to dust mass (qPAH), and we examined the relationships between these parameters. The final sample consisted of 48 galaxies, with redshifts from 0.04 to 2.36. The estimated qPAH values were lower on average than typical values in the literature. This could be due to various reasons, such as low metallicity, or ongoing active galactic nucleus or starburst activity. Of our sample, 83% of the objects fell in the star-forming main sequence of galaxies, while only 8% could be considered as starbursts. We found a decreasing qPAH trend with increasing AV and consequently LIR, suggesting the possible presence of compact star-forming regions. We compared the qPAH values with the known relations of the PAH luminosities, but they did not always follow the same trends (SFR, LIR), and showed only slight correlation with the PAH luminosities.

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 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 Scaling Relations between Gas and Star Formation in Nearby Galaxies

2010 ◽  
Vol 6 (S270) ◽  
pp. 327-334 ◽  
Author(s):  
Frank Bigiel ◽  
Adam Leroy ◽  
Fabian Walter
Keyword(s):  
Star Formation ◽  
Spatial Scales ◽  
Formation Rate ◽  
Star Forming ◽  
Multiple Regimes ◽  
Combining Data ◽  
Multi Wavelength ◽  
Nearby Galaxies ◽  
Physical Quantities ◽  
Individual Galaxy

AbstractHigh resolution, multi-wavelength maps of a sizeable set of nearby galaxies have made it possible to study how the surface densities of H i, H2 and star formation rate (ΣHI, ΣH2, ΣSFR) relate on scales of a few hundred parsecs. At these scales, individual galaxy disks are comfortably resolved, making it possible to assess gas-SFR relations with respect to environment within galaxies. ΣH2, traced by CO intensity, shows a strong correlation with ΣSFR and the ratio between these two quantities, the molecular gas depletion time, appears to be constant at about 2 Gyr in large spiral galaxies. Within the star-forming disks of galaxies, ΣSFR shows almost no correlation with ΣHI. In the outer parts of galaxies, however, ΣSFR does scale with ΣHI, though with large scatter. Combining data from these different environments yields a distribution with multiple regimes in Σgas – ΣSFR space. If the underlying assumptions to convert observables to physical quantities are matched, even combined datasets based on different SFR tracers, methodologies and spatial scales occupy a well define locus in Σgas – ΣSFR space.

scholarly journals High-J CO Intensity Measurements for Galaxies Observed by the Herschel FTS

2015 ◽  
Vol 11 (S315) ◽  
pp. 26-29
Author(s):  
Julia Kamenetzky ◽  
Naseem Rangwala ◽  
Jason Glenn ◽  
Philip Maloney ◽  
Alex Conley
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Raw Material ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
J 13 ◽  
Systematic Effects ◽  
Nearby Galaxies ◽  
Co Emission

AbstractMolecular gas is the raw material for star formation and is commonly traced by the carbon monoxide (CO) molecule. The atmosphere blocks all but the lowest-J transitions of CO for observatories on the ground, but the launch of the Herschel Space Observatory revealed the CO emission of nearby galaxies from J = 4−3 to J = 13−12. Herschel showed that mid- and high-J CO lines in nearby galaxies are emitted from warm gas, accounting for approximately 10% of the molecular mass, but the majority of the CO luminosity. The energy budget of this warm, highly-excited gas is a significant window into the feedback interactions among molecular gas, star formation, and galaxy evolution. Likely, mechanical heating is required to explain the excitation. Such gas has also been observed in star forming regions within our galaxy.We have examined all ~300 spectra of galaxies from the Herschel Fourier Transform Spectrometer and measured line fluxes or upper limits for the CO J = 4−3 to J = 13−12, [CI], and [NII] 205 micron lines in ~200 galaxies, taking systematic effects of the FTS into account. We will present our line fitting method, illustrate trends available so far in this large sample, and preview the full 2-component radiative transfer likelihood modeling of the CO emission using an illustrative sample of 20 galaxies, including comparisons to well-resolved galactic regions. This work is a comprehensive study of mid- and high-J CO emission among a variety of galaxy types, and can be used as a resource for future (sub)millimeter studies of galaxies with ground-based instruments.

scholarly journals The Spitzer spectroscopic survey of the Small Magellanic Cloud: polycyclic aromatic hydrocarbon emission from SMC star-forming regions

2008 ◽  
Vol 4 (S256) ◽  
pp. 160-165
Author(s):  
Karin M. Sandstrom ◽  
Alberto D. Bolatto ◽  
Snežana Stanimirović ◽  
J. D. T. Smith ◽  
Jacco Th. van Loon ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Physical State ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
Low Metallicity

AbstractBecause of its proximity, the Small Magellanic Cloud provides a unique opportunity to map the polycyclic aromatic hydrocarbon (PAH) emission from photo-dissociation regions (PDRs) in a low-metallicity (12 + log(O/H) ~ 8) galaxy at high spatial resolution in order to learn about their abundance and physical state. We present mid-IR spectral mapping observations of star-forming regions in the Small Magellanic Cloud obtained as part of the Spitzer Spectroscopic Survey of the SMC (S4MC) project. These observations allow us to map the distribution of PAH emission in these regions and the measure the variation of PAH band strengths with local physical conditions. In these proceedings we discuss preliminary results on the physical state of the PAHs, in particular their ionization fraction.

scholarly journals Star formation on galactic scales

2006 ◽  
Vol 2 (S237) ◽  
pp. 311-316
Author(s):  
Robert C. Kennicutt
Keyword(s):  
Star Formation ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Multi Wavelength ◽  
Nearby Galaxies

AbstractNew multi-wavelength data on nearby galaxies are providing a much more accurate and complete observational picture of star formation on galactic scales. Here I briefly report on recent results from the Spitzer Infrared Nearby Galaxies Survey (SINGS). These provide new constraints on the frequency and lifetime of deeply obscured star-forming regions in galaxies, the measurement of dust-corrected star formation rates in galaxies, and the form of the spatially-resolved Schmidt law.

scholarly journals SK 1: A possible case of triggered star formation in perseus

2006 ◽  
Vol 2 (S237) ◽  
pp. 217-221
Author(s):  
Miriam Rengel ◽  
Klaus Hodapp ◽  
Jochen Eislöffel
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Dust Shell ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Suitable Target

AbstractAccording to a triggered star formation scenario (e.g. Martin-Pintado & Cernicharo 1987) outflows powered by young stellar objects shape the molecular clouds, can dig cavities, and trigger new star formation. NGC 1333 is an active site of low- and intermediate star formation in Perseus and is a suggested site of self-regulated star formation (Norman & Silk 1980). Therefore it is a suitable target for a study of triggered star formation (e.g. Sandell & Knee 2001, SK1). On the other hand, continuum sub-mm observations of star forming regions can detect dust thermal emission of embedded sources (which drive outflows), and further detailed structures.Within the framework of our wide-field mapping of star formation regions in the Perseus and Orion molecular clouds using SCUBA at 850 and 450 μm, we mapped NCG 1333 with an area of around 14′× 21′. The maps show more structure than the previous maps of the region observed in sub-mm. We have unveiled the known embedded SK 1 source (in the dust shell of the SSV 13 ridge) and detailed structure of the region, among some other young protostars.In agreement with the SK 1 observations, our map of the region shows lumpy filaments and shells/cavities that seem to be created by outflows. The measured mass of SK 1 (~0.07 M) is much less than its virial mass (~0.2-1 M). Our observations support the idea of SK 1 as an event triggered by outflow-driven shells in NGC 1333 (induced by an increase in gas pressure and density due to radiation pressure from the stellar winds that have presumably created the dust shell). This kind of evidences provides a more thorough understanding of the star formation regulation processes.

scholarly journals The EDGE-CALIFA survey: Self-regulation of Star formation at kpc scales

2021 ◽  
Author(s):  
J K Barrera-Ballesteros ◽  
S F Sánchez ◽  
T Heckman ◽  
T Wong ◽  
A Bolatto ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Self Regulation ◽  
Stellar Mass ◽  
Good Representation ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Range ◽  
Two Parameters ◽  
Stellar Masses

Abstract The processes that regulate star formation are essential to understand how galaxies evolve. We present the relation between star formation rate density, ΣSFR , and hydrostatic midplane pressure, Ph , for 4260 star-forming regions of kpc size located in 96 galaxies included in the EDGE-CALIFA survey covering a wide range of stellar masses and morphologies. We find that these two parameters are tightly correlated, showing a smaller scatter in comparison to other star-forming relations. A power-law, with a slightly sub-linear index, is a good representation of this relation. Its residuals show a significant anti-correlation with both stellar age and metallicity whereas the total stellar mass may also play a secondary role in shaping the ΣSFR - Ph relation. For actively star-forming regions we find that the effective feedback momentum per unit stellar mass (p*/m*), measured from the Ph/ΣSFR ratio increases with Ph. The median value of this ratio for all the sampled regions is larger than the expected momentum just from supernovae explosions. Morphology of the galaxies, including bars, does not seem to have a significant impact in the ΣSFR - Ph relation. Our analysis indicates that local ΣSFR self-regulation comes mainly from momentum injection to the interstellar medium from supernovae explosions. However, other mechanisms in disk galaxies may also play a significant role in shaping the ΣSFR at kpc scales. Our results also suggest that Ph is the main parameter that modulates star formation at kpc scales, rather than individual components of the baryonic mass.

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