Radio emission from a possible supernova remnant in the galaxy NGC 4449

Seaquist, E. R.; Bignell, R. C.

doi:10.1086/182818

Cited by 34 publications

(30 citation statements)

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“…The observed ultra-dense H ii regions are produced when hot massive stars within the clusters ionize the surrounding gas and are identified as compact free-free (thermal) radio sources. A previous catalog of radio-detected H ii regions in NGC 4449 was presented by Israel (1980) using an NRAO 3 three-element image at 11 cm (2.7 GHz) from Seaquist & Bignell (1978) with a beam size of 10. 8 × 6.…”

Section: No 6 2008 Emerging Massive Star Clusters 2223mentioning

confidence: 99%

Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 From the Radio to the Ultraviolet

Reines¹,

Johnson²,

Goss³

2008

The Astronomical Journal

101

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We present a multi-wavelength study of embedded massive clusters in the nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution. By combining high-resolution imaging from the radio to the ultraviolet, we reveal these clusters to be in the process of emerging from their gaseous and dusty birth cocoons. We use Very Large Array (VLA) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense H ii regions, detectable via their production of thermal freefree radio continuum. Ultraviolet, optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison. We detect 39 compact radio sources toward NGC 4449 at 3.6 cm using the highest resolution (1. 3) and sensitivity (∼12 µJy) VLA image of the galaxy to date. We reliably identify 13 thermal radio sources and derive their physical properties using both nebular emission from the H ii regions and spectral energy distribution fitting to the stellar continuum. These radio-detected clusters have ages 5 Myr and stellar masses of order 10 4 M . The measured extinctions are quite low: 12 of the 13 thermal radio sources have A V 1.5, while the most obscured source has A V ≈ 4.3. By combining results from the nebular and stellar emission, we find an I-band excess that is anti-correlated with cluster age and an apparent mass-age correlation. Additionally, we find evidence that local processes such as supernovae and stellar winds likely play an important role in triggering the current bursts of star formation within NGC 4449.

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Section: No 6 2008 Emerging Massive Star Clusters 2223mentioning

confidence: 99%

Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 From the Radio to the Ultraviolet

Reines¹,

Johnson²,

Goss³

2008

The Astronomical Journal

101

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“…In the nearby Magellanic irregular galaxy, NGC 4449, there is a remarkable object, discovered by Seaquist & Bignell (1978) in the radio. The non‐thermal radio spectrum and observations of both broad and narrow optical lines (e.g.…”

Section: Introductionmentioning

confidence: 99%

The first VLBI image of the young, oxygen-rich supernova remnant in NGC 4449

Bietenholz

Bartel

Milisavljevic

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We report on sensitive 1.4‐GHz VLBI radio observations of the unusually luminous supernova remnant SNR 4449‐1 in the galaxy NGC 4449, which gave us the first well‐resolved image of this object. The remnant's radio morphology consists of two approximately parallel bright ridges, suggesting similarities to the barrel shape seen for many older Galactic supernova remnants or possibly to SN 1987A. The angular extent of the remnant is 65 × 40 mas, corresponding to (3.7 × 2.3) × 1018 (D/3.8 Mpc) cm. We also present a new, high signal‐to‐noise ratio optical spectrum. By comparing the remnant's linear size to the maximum velocities measured from optical lines, as well as using constraints from historical images, we conclude that the supernova explosion occurred between ∼1905 and 1961, likely around 1940. The age of the remnant is therefore likely ∼70 yr. We find that SNR 4449‐1's shock wave is likely still interacting with the circumstellar rather than interstellar medium.

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“…The SNR was first discovered in radio by Seaquist & Bignell (1978) as a bright, unresolved nonthermal radio source ($10 mJy at 2.7 GHz) approximately 1 0 north of the nucleus of the galaxy at a location nearly coincident with an H ii region cataloged by Sabbadin & Bianchini (1979). Subsequent optical spectrophotometry showed two different types of line emissions: (1) narrow H ii region-like lines, and (2) broad lines of forbidden oxygen attributable to a young SNR like Cas A (Balick & Heckman 1978).…”

Section: Introductionmentioning

confidence: 99%

The Nature of the Ultraluminous Oxygen‐Rich Supernova Remnant in NGC 4449

Milisavljevic

Fesen

2008

ApJ

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Optical images and spectra, both ground based and taken by Hubble Space Telescope (HST ), of the young, luminous O-rich supernova remnant in the irregular galaxy NGC 4449 are presented. HST images of the remnant and its local region were obtained with the ACS/ WFC using filters F435W, F555W, F814W (B, V, and I, respectively),, and F550M (line-free continuum). These images show an unresolved remnant ( FWHM < 0:05 00 ) located within a rich cluster of OB stars which itself is enclosed by a nearly complete interstellar shell seen best in H + [N ii] emission approximately 8 00 ; 6 00 (150 pc ; 110 pc) in size. The remnant and its associated OB cluster are isolated from two large nearby H ii regions. The ACS [O iii] image shows the remnant may be partially surrounded by a clumpy ring of emission approximately 1 00 ($20 pc) in diameter. Recent ground-based spectra of the remnant reveal (1) the emergence of broad, blueshifted emission lines of [S ii] kk6716, 6731, [Ar iii] k7136, and [Ca ii] kk7291, 7324 which were not observed in spectra taken in 1978Y1980; (2) faint emission at 6540Y6605 8 centered about H and [ N ii] kk6548, 6583 with an expansion velocity of 500 AE 100 km s À1 ; and (3) excess emission around 4600Y4700 8 suggestive of a Wolf-Rayet population in the remnant's star cluster. We use these new data to re-interpret the origin of the remnant's prolonged and bright luminosity and propose that the remnant is strongly interacting with dense, circumstellar wind loss material from a k20 M progenitor star.

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Radio emission from a possible supernova remnant in the galaxy NGC 4449

Cited by 34 publications

References 0 publications

Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 From the Radio to the Ultraviolet

Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 From the Radio to the Ultraviolet

The first VLBI image of the young, oxygen-rich supernova remnant in NGC 4449

The Nature of the Ultraluminous Oxygen‐Rich Supernova Remnant in NGC 4449

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