Super Star Clusters in the Central Starburst of NGC 4945

Emig, K. L.; Bolatto, Alberto D.; Leroy, Adam K.; Mills, Elisabeth A. C.; Jiménez-Donaire, María J.; Tielens, A. G. G. M.; Ginsburg, Adam; Gorski, Mark; Krieger, Nico; Levy, Rebecca C.; Meier, David S.; Ott, J.; Rosolowsky, Erik; Thompson, Todd A.; Veilleux, Sylvain

doi:10.3847/1538-4357/abb67d

Cited by 34 publications

(56 citation statements)

References 64 publications

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“…From our new estimate of the total stellar masses of the embedded clusters, we find that this is comparable to the total gas mass associated with these sources from L18 (Table 4). This suggests that many of these sources are still in the process of forming and supports the assumption of a ZAMS population for the overall NGC 253 starburst, compared to the older burst age of 5 Myr adopted by Emig et al (2020) for the central starburst in NGC 4945.…”

Section: Evolution Of the Starburstsupporting

confidence: 76%

“…Additionally, we can also make a direct comparison with NGC 4945 to determine a relative age for the two bursts. As seen in Emig et al (2020), there is substantially more nonthermal emission (due to supernova remnants) intermixed with the cluster emission. The clusters in NGC 4945 also have smaller gas fractions (typically an order of magnitude less than the stellar mass).…”

mentioning

confidence: 89%

“…We first use the estimated free-free contributions to the 3 mm continuum flux to derive electron temperatures for sources 4, 5, 9, and 14. To determine the electron temperature T e , we use the formula derived in Appendix A of Emig et al (2020), based on Draine (2011) and Gordon & Sorochenko (2002): ), R LC is the ratio of the line-to-continuum emission, and ν is the frequency of the recombination line in GHz.…”

Section: The Electron Temperaturementioning

confidence: 99%

“…A weak AGN is also unlikely to be responsible for ionizing this gas, given that observations of submillimeter recombination lines around the luminous Type II Seyfert NGC 1068 have failed to detect emission (Izumi et al 2016). The AGN in starburst galaxy NGC 4945 has also been shown not to dominate the ionization of the nuclear region (Marconi et al 2000;Spoon et al 2000;Emig et al 2020). Models further predict that in the presence of an AGN, recombination lines from He ++ would be stronger than the hydrogen recombination lines (Scoville & Murchikova 2013), and we do not detect any emission from the HeII (64) α line at 98.0795642 GHz.…”

Section: The Nature Of the Broad Line Width H40α Emissionmentioning

confidence: 99%

“…The masses we derive are sensitive to the assumption of the age of the stellar population. Cluster masses derived for NGC 4945 (Emig et al 2020), for which the estimated age of the starburst is 5 Myr, are substantially more massive, as an older stellar population produces fewer ionizing photons per unit mass. Adopting a burst age of 5 Myr for NGC 253 would increase the masses derived here by about an order of magnitude.…”

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confidence: 99%

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Clustered Star Formation in the Center of NGC 253 Contributes to Driving the Ionized Nuclear Wind

Mills

Gorski

Emig

et al. 2021

ApJ

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We present new 3 mm observations of the ionized gas toward the nuclear starburst in the nearby (D ∼ 3.5 Mpc) galaxy NGC 253. With ALMA, we detect emission from the H40α and He40α lines in the central 200 pc of this galaxy on spatial scales of ∼4 pc. The recombination line emission primarily originates from a population of approximately a dozen embedded super star clusters in the early stages of formation. We find that emission from these clusters is characterized by electron temperatures ranging from 7000 to 10,000 K and measures an average singly ionized helium abundance 〈Y + 〉 = 0.25 ± 0.06, both of which are consistent with values measured for H II regions in the center of the Milky Way. We also report the discovery of unusually broad line width recombination line emission originating from seven of the embedded clusters. We suggest that these clusters contribute to the launching of the large-scale hot wind observed to emanate from the central starburst. Finally, we use the measured recombination line fluxes to improve the characterization of overall embedded cluster properties, including the distribution of cluster masses and the fractional contribution of the clustered star formation to the total starburst, which we estimate is at least 50%.Unified Astronomy Thesaurus concepts: Interstellar medium (847); H II regions (694); Young star clusters (1833)

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Section: Evolution Of the Starburstsupporting

confidence: 76%

mentioning

confidence: 89%

Section: The Electron Temperaturementioning

confidence: 99%

Section: The Nature Of the Broad Line Width H40α Emissionmentioning

confidence: 99%

mentioning

confidence: 99%

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Clustered Star Formation in the Center of NGC 253 Contributes to Driving the Ionized Nuclear Wind

Mills

Gorski

Emig

et al. 2021

ApJ

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Filamentary structures of ionized gas in Cygnus X

Emig

White

Salas³

et al. 2022

A&A

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Context. Ionized gas probes the influence of massive stars on their environment. The Cygnus X region (d ~ 1.5 kpc) is one of the most massive star-forming complexes in our Galaxy, within which the Cyg OB2 association (age of 3–5 Myr and stellar mass 2 × 104 M⊙) has a dominant influence. Aims. We observe the Cygnus X region at 148 MHz using the Low Frequency Array (LOFAR) and take short-spacing information into account during image deconvolution into account. Together with data from the Canadian Galactic Plane Survey, we investigate the morphology, distribution, and physical conditions of low-density ionized gas in a 4° × 4° (~100 pc × 100 pc) region at a resolution of 2′ (0.9 pc). Methods. The Galactic radio emission in the region analyzed is almost entirely thermal (free-free) at 148 MHz, with emission measures (EM) of 103 < EM [pc cm−6] < 106. As filamentary structure is a prominent feature of the emission, we use DisPerSE and Fil ChaP to identify filamentary ridges and characterize their radial (EM) profiles. Results. The distribution of radial profiles has a characteristic width of 4.3 pc and a power-law distribution (β = −1.8 ± 0.1) in peak EM down to our completeness limit of 4200 pc cm−6. The electron densities of the filamentary structure range between 10 ≲ ne [cm−3] ≲ 400 with a median value of 35 cm−3, remarkably similar to [N II] surveys of ionized gas. Conclusions. Cyg OB2 may ionize at most two-thirds of the total ionized gas and the ionized gas in filaments. More than half of the filamentary structures are likely photoevaporating surfaces flowing into a surrounding diffuse (~5 cm−3) medium. However, this is likely not the case for all ionized gas ridges. A characteristic width in the distribution of ionized gas indicates that the stellar winds of Cyg OB2 create a fraction of the ionized filaments through swept-up ionized gas or dissipated turbulence.

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Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI

Butterworth,

Viti,

Van der Werf

et al. 2024

A&A

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Determining the evolution of the CNO isotopes in the interstellar medium (ISM) of starburst galaxies can yield important constraints on the ages of super star clusters (SSCs), or on other aspects and factors contributing to their evolution, such as the initial mass function (IMF). Due to the time-dependent nature of the abundances of isotopes within the ISM ---as they are supplied from processes such as nucleosynthesis or chemical fractionation---, this provides the opportunity to test whether or not isotope ratios trace the ages of highly star-forming regions, such as SSCs. The goal of this study is to investigate whether the isotopic variations in SSC regions within NGC 253 are correlated with their different ages as derived from stellar population modelling. We measured abundance ratios of CO, HCN, and HCO isotopologues in six regions containing SSCs within NGC 253 using high-spatial-resolution (1.6",$ 28$pc) data from the ALCHEMI (ALma Comprehensive High-resolution Extragalactic Molecular Inventory) ALMA Large program. We then analysed these ratios using RADEX radiative transfer modelling, with the parameter space sampled using the nested sampling Monte Carlo algorithm MLFriends. These abundance ratios were then compared to ages predicted in each region via the fitting of observed star-formation tracers (such as Brgamma ) to Starburst99 starburst stellar population evolution models. We determined the isotopic column density ratios across multiple regions of SSC activity in NGC 253 using non-LTE radiative transfer modelling. We do not find any significant trend with age for the CO and HCN isotopologue ratios on timescales of the ages of the SSC* regions observed. However, HCO may show a correlation with age over these timescales in C/ C. The driving factors of these ratios within SSCs could be the IMF or fractionation effects. To further probe these effects in SSCs over time, a larger sample of SSCs must be observed spanning a larger age range.

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Super Star Clusters in the Central Starburst of NGC 4945

Cited by 34 publications

References 64 publications

Clustered Star Formation in the Center of NGC 253 Contributes to Driving the Ionized Nuclear Wind

Clustered Star Formation in the Center of NGC 253 Contributes to Driving the Ionized Nuclear Wind

Filamentary structures of ionized gas in Cygnus X

Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI

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