Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

Ando, Ryo; Nakanishi, Koichiro; Kohno, Kotaro; Izumi, Teruo; Martín, S.; Harada, Nanase; Takano, Shuro; Kuno, Nario; Nakai, Naomasa; Sugai, Hajime; Saito, Kazuo; Tosaki, Tomoka; Matsubayashi, Kazuya; Nakajima, Taku; Nishimura, Y.; Tamura, Motohide

doi:10.3847/1538-4357/aa8fd4

Cited by 33 publications

(36 citation statements)

References 59 publications

(86 reference statements)

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“…Then one expects that the difference in the evolutionary stage found in the SSCs in NGC 253 will have an impact in the chemical richness of the molecular gas in SSCs. In fact, Ando et al (2017) found that at scales of 10 pc (at a lower resolution than in this work) the HNCO and CH 3 OH abundances dramatically decreases in two of their sources, which actually contain our ZAMS-SSCs 10, 11, 12 and 9. Martín et al (2008Martín et al ( , 2009) have found that the HNCO/CS ratio is an excellent tracer of gas affected by UV radiation since HNCO is much more easily dissociated than CS (which is still abundant in PDRs).…”

Section: Radiative Feedbackcontrasting

confidence: 42%

Super Hot Cores in NGC 253: witnessing the formation and early evolution of super star clusters

Rico-Villas

Martı́n-Pintado

González-Alfonso

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Using 0.2 (∼ 3 pc) ALMA images of vibrationally excited HC 3 N emission (HC 3 N * ) we reveal the presence of 8 unresolved Super Hot Cores (SHCs) in the inner 160 pc of NGC 253. Our LTE and non-LTE modelling of the HC 3 N * emission indicate that SHCs have dust temperatures of 200 − 375 K, relatively high H 2 densities of 1 − 6 × 10 6 cm −3 and high IR luminosities of 0.1−1×10 8 L . As expected from their short lived phase (∼ 10 4 yr), all SHCs are associated with young Super Star Clusters (SSCs). We use the ratio of luminosities form the SHCs (protostar phase) and from the free-free emission (ZAMS star phase), to establish the evolutionary stage of the SSCs. The youngest SSCs, with the larges ratios, have ages of a few 10 4 yr (proto-SSCs) and the more evolved SSCs are likely between 10 5 and 10 6 yr (ZAMS-SSCs). The different evolutionary stages of the SSCs are also supported by the radiative feedback from the UV radiation as traced by the HNCO/CS ratio, with this ratio being systematically higher in the young proto-SSCs than in the older ZAMS-SSCs. We also estimate the SFR and the SFE of the SSCs. The trend found in the estimated SFE (∼ 40% for proto-SSCs and > 85% for ZAMS-SSCs) and in the gas mass reservoir available for star formation, one order of magnitude higher for proto-SSCs, suggests that star formation is still going on in proto-SSCs. We also find that the most evolved SSCs are located, in projection, closer to the center of the galaxy than the younger proto-SSCs, indicating an inside-out SSC formation scenario.

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Section: Radiative Feedbackcontrasting

confidence: 42%

Super Hot Cores in NGC 253: witnessing the formation and early evolution of super star clusters

Rico-Villas

Martı́n-Pintado

González-Alfonso

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…From earlier low resolution observations (> 20 pc, e.g. Sakamoto et al 2006Sakamoto et al , 2011 to recent observations at high resolution (8 pc × 5 pc in Ando et al 2017 and 2 pc in Leroy et al 2018) the number of molecular clumps associated the starburst increased from ∼ 5 to 14. These studies find the clumps to be massive (4 − 10 × 10 4 M ), compact (< 10 pc), chemically rich (up to > 19 molecules detected in the 0.8 mm band) and hot (up to 90 K).…”

Section: Introductionmentioning

confidence: 70%

“…Note that these rough estimates depend on the assumption of no acceleration (positive, nor negative) of the outflow after being launched from the disk which might be a close enough approximation on these scales of a few hundred parsecs. The very young ( 1 Myr) and still deeply embedded super star cluster discussed recently by Ando et al (2017) and Leroy et al (2018) are most likely too young to have affected the observed molecular outflow.…”

Section: Outflow Energy and Momentummentioning

confidence: 92%

The Molecular Outflow in NGC 253 at a Resolution of Two Parsecs

Krieger

Bolatto

Walter

et al. 2019

ApJ

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We present 0.15 (∼ 2.5 pc) resolution ALMA CO(3-2) observations of the starbursting center in NGC 253. Together with archival ALMA CO(1-0) and CO(2-1) data we decompose the emission into a disk and non-disk component. We find ∼ 7 − 16% of the CO luminosity to be associated with the non-disk component (1.2 − 4.2 × 10 7 K km s −1 pc 2 ). The total molecular gas mass in the center of NGC 253 is ∼ 3.6 × 10 8 M with ∼ 0.5 × 10 8 M (∼ 15%) in the non-disk component. These measurements are consistent across independent mass estimates through three CO transitions. The high-resolution CO(3-2) observations allow us to identify the molecular outflow within the non-disk gas. Using a starburst conversion factor, we estimate the deprojected molecular mass outflow rate, kinetic energy and momentum in the starburst of NGC 253. The deprojected molecular mass outflow rate is in the range ∼ 14 − 39 M yr −1 with an uncertainty of 0.4 dex. The large spread arises due to different interpretations of the kinematics of the observed gas while the errors are due to unknown geometry. The majority of this outflow rate is contributed by distinct outflows perpendicular to the disk, with a significant contribution by diffuse molecular gas. This results in a mass loading factor η =Ṁ out /Ṁ SFR in the range η ∼ 8 − 20 for gas ejected out to ∼ 300 pc. We find the kinetic energy of the outflow to be ∼ 2.5 − 4.5 × 10 54 erg and ∼ 0.8 dex typical error which is ∼ 0.1% of the total or ∼ 8% of the kinetic energy supplied by the starburst. The outflow momentum is 4.8 − 8.7 × 10 8 M km s −1 (∼ 0.5 dex error) or ∼ 2.5 − 4% of the kinetic momentum released into the ISM by feedback. The unknown outflow geometry and launching sites are the primary source of uncertainty in this study.

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“…In spite of the similarity of the chemical composition at a scale of molecular clouds, a different chemical composition has been found in metal poor galaxies (Nishimura et al 2016a,b), shocked regions of merging galaxies (e.g. Saito et al 2017;Ueda et al 2017), and nuclear regions of galaxies observed at a scale of a few hundred pc (e.g., Costagliola et al 2015;Meier et al 2015;Ando et al 2017). In these objects, the chemical compositions are thought to reflect low elemental abundances, gas dynamics at molecular cloud scales, and extreme environments due to feedback from nuclear activity and vigorous star-formation.…”

Section: Chemical Compositions Of Molecular Cloudsmentioning

confidence: 99%

A 3 mm Spectral Line Survey toward the Barred Spiral Galaxy NGC 3627

Watanabe

Nishimura

Saito

et al. 2019

ApJS

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We conduct spectral line survey observations in the 3 mm band toward a spiral arm, a bar-end, and a nuclear region of the nearby barred spiral galaxy NGC 3627 with the IRAM 30 m telescope and the Nobeyama 45 m telescope. Additional observations are performed toward the spiral arm and the bar-end in the 2 mm band. We detect 8, 11, and 9 molecular species in the spiral arm, the bar-end, and the nuclear region, respectively. Star-formation activities are different among the three regions, and in particular, the nucleus of NGC 3627 is known as a LINER/Seyfert 2 type nucleus. In spite of these physical differences, the chemical composition shows impressive similarities among the three regions. This result means that the characteristic chemical composition associated with 2. Observations IRAM 30 m TelescopeObservations toward SA and BE in NG 3627 were performed with the IRAM 30 m telescope at Pico Veleta in July, 2014 and December, 2014. The observed positions are shown in Figure 1 and Table 1. The beam sizes are 30-20 ′′ and 19-17 ′′ at the 3 mm and 2 mm band, respectively, which correspond to linear scales of 1.2-0.9 kpc and 0.8-0.7 kpc at the distance of 11.1 Mpc, respectively. The observed frequency range is from 85.0 to 116.0 GHz and from 140.0 to 148.0 GHz for SA, while it is from 85.0 to 100.5 GHz, from 108.4 to 116.0 GHz, and from 140.0 to 148.0 GHz for BE. The frequency range from 100.5 to 108.4 GHz does not involve strong spectral lines according to previous spectral line surveys toward the spiral arm of M51 (Watanabe et al. 2014). Therefore, we put a lower priority on this frequency range, and did not observe it for BE because of the limited observation time. Two EMIR (Eight MIxer Receivers) bands, E090 and E150, were used simultaneously with the dual polarization mode. The EMIR is the sideband separating receiver, which outputs the USB and LSB signals separately. The image rejection ratio is confirmed to be better than 13 dB and 10 dB for E090 and E150, respectively, according to the status report of the 30 m telescope 1 . The system noise temperature ranged from 75 to 310 K for E090 and from 100 to 210 K for E150. Detailed frequency settings and system noise temperatures are summarized in Table 3. Backends were eight FTS (Fourier Transform Spectrometers) autocorrelators whose bandwidth and channel width are 4050 MHz and 195 kHz, respectively. The telescope pointing was checked every hour by observing the continuum source 1055+018 near the target position, and was found to be better than ±5 ′′ . The wobbler switching mode was employed with beam throw of ±120 ′′ and switching frequency of 0.5 Hz. The wobbler throw is toward the azimuth direction, and hence, the absolute off-position depends on the hour angle. Nevertheless, the off-position was always out of the CO disk of NGC 3627. The intensity scale was calibrated to the antenna temperature (T * A ) scale by using cold and hot loads. T * A was converted to the main beam temperature T mb by multiplying F eff /B eff . Here, F eff is the forward efficiency, w...

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Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

Cited by 33 publications

References 59 publications

Super Hot Cores in NGC 253: witnessing the formation and early evolution of super star clusters

Super Hot Cores in NGC 253: witnessing the formation and early evolution of super star clusters

The Molecular Outflow in NGC 253 at a Resolution of Two Parsecs

A 3 mm Spectral Line Survey toward the Barred Spiral Galaxy NGC 3627

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