Integral-field near-infrared spectroscopy of two blue dwarf galaxies: NGC 5253 and He 2-10

Cresci, G.; Vanzi, L.; Sauvage, M.; Santangelo, G.; Werf, P. van der

doi:10.1051/0004-6361/201014864

Cited by 21 publications

(27 citation statements)

References 64 publications

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“…Non-LTE modeling of this ratio using RADEX 6 indicates a minimum kinetic temperature of T K > 200 K for the 1σ lower limit, and T K > 350 K for the adopted value of I 32 /I 21 = 2.25 (see Methods). The high gas temperature is consistent with a thermal origin for H 2 2.2µm emission in the region 7 . Cloud D appears to be a Photon-Dominated Region (PDR), heated by ultraviolet radiation from the several thousand cluster O stars in the cluster 4,8 .…”

supporting

confidence: 76%

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Turner

Beck

Benford

et al. 2015

Nature

103

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Gas clouds in present-day galaxies are inefficient at forming stars. Low star formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly fourteen billion years after the Big Bang 1 and why star clusters generally do not survive their births, instead dispersing to form galactic disks, halos, or bulges 2 . Yet the existence of ancient massive star clusters in the Milky Way, globular clusters, suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC 5253, has a young star cluster that may provide an example of highly efficient star formation 3 . Here we report the detection of the J= 3-2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent, and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star formation efficiency exceeds 50%, ten times higher than clouds in the Milky Way: this cloud is a factory of stars and soot. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.The Submillimeter Array image of NGC 5253, shown in Figure 1, reveals a bright CO(3-2) source coincident with the giant cluster and its "supernebula" 4 . "Cloud D" 3 is one of only two molecular clouds detected within the galaxy; the second cloud is smaller and located ~5" (90 pc) to the southwest. A "streamer" of gas extending along the minor axis is also detected in CO(3-2). This streamer, previously detected in lower J CO lines, appears to be falling into the galaxy near the supernebula 3,5 . Both the streamer and Cloud D emit 870µm continuum emission, as shown in Figure 2. Also shown is an image of 350µm continuum, in which both Cloud D and the streamer are detected. Figure 1. CO J=3-2 emission in NGC 5253. The SMA CO(3-2) integrated line intensity, in red, is shown atop a λ814nm Hubble Space Telescope image. The SMA beam is 4" x 2" (74 pc x 37 pc). The field covers 40" x 40" (740 pc x740 pc), north up, east left. Image registration is to < 1". The CO streamer coincides with the optical dust lane to the east. The massive star cluster is located at the bright CO peak, Cloud D; it is embedded 8.9 , and not visible here. Cloud F is to the southwest of Cloud D.The molecular gas in Cloud D is hot. This is clear from the increase in brightness from CO(2-1) 3 to CO(3-2). The intensity ratio of the two lines is I 32 /I 21 = 2.6±0.5 (I line = ∫T line dv). This ratio is nonthermal, although the thermal limit of 2.25 (~ν 2 ) is within the uncertainties, and is what we adopt. Non-LTE modeling of this ratio using RADEX 6 indicates a minimum kinetic temperature of T K > 200 K for the 1σ lower limit, and T K > 350 K for the adopted value of I 32 /I 21 = 2.25 (see Methods). The high gas temperature is consistent with a thermal origin for H 2 2.2µm emission in the region 7 . Cloud D appears to be a Photon-Dominated Region (PDR), heated by ultraviol...

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supporting

confidence: 76%

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Turner

Beck

Benford

et al. 2015

Nature

103

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“…It is likely that the older star formation triggered the most recent one. Successive episodes of star formation triggering one another have been hypothesized (Cresci et al 2010). This idea finds further support in the comparison of the distribution of [FeII] relative to H 2 .…”

Section: Discussionmentioning

confidence: 60%

“…If we compare all galaxies observed so far mainly, II Zw 40 (Vanzi et al 2008), NGC 5253, He 2-10 ( Cresci et al 2010), NGC 3125 and SBS 0335-052, we can highlight the following points: 1) in all galaxies we observe young massive clusters. A few of them are younger than 2−3 Myr and are surrounded by large HII regions.…”

Section: Discussionmentioning

confidence: 85%

“…We wish to establish whether our observation is consistent with the SN rate reported in the literature. To do so we refer to relation (1) of Cresci et al (2010), which relates the [FeII] luminosity to the SN rate using, as they do, a constant α = 0.24×(10 40 erg/s yr) −1 . The [FeII] luminosity of 8.6 × 10 37 erg/s would provide a SN rate of 2 × 10 −3 SN/yr.…”

Section: Ionized Ironmentioning

confidence: 99%

“…In this way we have access to a number of unique features that characterize the star formation environment. As part of this investigation we have already published results on three relevant objects: II Zw 40 (Vanzi et al 2008), He 2-10 and NGC 5253 (Cresci et al 2010). All these galaxies are nearby irregular blue dwarfs undergoing powerful episodes of star formation, as such they reveal the details star formation on a large scale.…”

Section: Introductionmentioning

confidence: 99%

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Integral field spectroscopy in the near infrared of NGC 3125-A and SBS 0335-052

Vanzi

Cresci

Sauvage

et al. 2011

A&A

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We present integral field spectroscopy in the near infrared of the nearby dwarf starburst galaxy NGC 3125-A and of the low metallicity dwarf galaxy SBS 0335-052. The use of adaptive optics in the observations produces sub-arcsecond angular resolution. We pinpoint the star forming cores of both galaxies, identify relevant ISM components such as dust, photo ionized gas, shock excited gas and molecular gas. We relate these components to the large scale star formation process of the galaxies. In particular we find the emission of the near infrared lines of H 2 and especially [FeII] does not coincide with the HII region in NGC 3125. We have the first clear detection of [FeII] in SBS 0335-052.

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VLT/X-shooter observations of blue compact galaxies Haro 11 and ESO 338-IG 004

Гусева

Izotov

Fricke

et al. 2012

A&A

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Context. Strongly star-forming galaxies of subsolar metallicities are typical of the high-redshift universe. Here we therefore provide accurate data for two low-z analogs, the well-known low-metallicity emission-line galaxies Haro 11 and ESO 338-IG 004. Aims. Our main goal is to derive their spectroscopic properties and to examine whether a previously reported near-infrared (NIR) excess in Haro 11 can be confirmed. Methods. On the basis of Very Large Telescope/X-shooter spectroscopic observations in the wavelength range ∼λλ3000-24 000 Å, we use standard direct methods to derive physical conditions and element abundances. Furthermore, we use X-shooter data together with Spitzer observations in the mid-infrared range to attempt to find hidden star formation. Results. We derive interstellar oxygen abundances of 12 + log O/H = 8.33 ± 0.01, 8.10 ± 0.04, and 7.89 ± 0.01 in the two H ii regions B and C of Haro 11 and in ESO 338-IG 004, respectively. The observed fluxes of the hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value of the extinction coefficient C(Hβ) across the entire wavelength range from the near-ultraviolet to the NIR and mid-infrared for each of the studied H ii regions. Thus, we confirm our previous findings obtained for several low-metallicity emission-line galaxies (Mrk 59, II Zw 40, Mrk 71, Mrk 996, SBS 0335-052E, PHL 293B, and GRB HG 031203) that the extinction coefficient C(Hβ) is not higher in the NIR than in the optical range and therefore that there are no emission-line regions contributing to the line emission in the NIR range, which are hidden in the optical range. The agreement between the extinction-corrected and CLOUDY-predicted fluxes implies that a H ii region model including only stellar photoionisation is able to account for the observed fluxes, in both the optical and NIR ranges. No additional excitation mechanism such as shocks from stellar winds and supernova remnants is needed. All observed spectral energy distributions (SEDs) can be reproduced quite well across the whole wavelength range by model SEDs except for Haro 11B, where there is a continuum flux excess at wavelengths >1.6 μm. It is possible that one or more red supergiant stars are responsible for the NIR flux excess in Haro 11B. We find evidence of a luminous blue variable (LBV) star in Haro 11C.

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Integral-field near-infrared spectroscopy of two blue dwarf galaxies: NGC 5253 and He 2-10

Cited by 21 publications

References 64 publications

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Integral field spectroscopy in the near infrared of NGC 3125-A and SBS 0335-052

VLT/X-shooter observations of blue compact galaxies Haro 11 and ESO 338-IG 004

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