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Title: Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited

Abstract

We present neutral hydrogen, ultraviolet, optical and near-infrared imaging, as well as optical spectroscopic observations of Minkowski's Object (MO), a star forming system at the end of a radio jet associated with NGC541 at the center of a cluster of galaxies, Abell 194. The observations strengthen the evidence, first presented in 1985, that MO is a small, peculiar galaxy in which the star formation has been triggered by the radio jet. Key new results are the discovery of a double H I cloud with a mass of 4.9 x 10{sup 8} M{sub {circle_dot}} straddling the radio jet downstream from MO at the location where the jet changes direction and decollimates; a strong detection of MO at near- and far-UV wavelengths and in H{alpha}, both of which also show a double structure; and what appear to be numerous H II regions and associated clusters in MO. The UV morphology of MO along the radio jet resembles the radio-aligned, rest-frame UV morphologies seen in many high redshift radio galaxies, which are also thought to be caused by jet-induced star formation. The UV, optical, and near-IR data show that the stellar population is dominated by a 7.5Myr-old instantaneous burst, with a total stellarmore » mass of 1.9 x 10{sup 7} M{sub {circle_dot}}.« less

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
899106
Report Number(s):
UCRL-JRNL-219648
TRN: US200706%%492
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, vol. 647, N/A, August 20, 2006, pp. 1040
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; CLOUDS; DETECTION; GALAXIES; HYDROGEN; MORPHOLOGY; RADIO GALAXIES; STARS; WAVELENGTHS

Citation Formats

Croft, S, van Breugel, W, de Vries, W, Dopita, M, Martin, C, Morganti, R, Neff, S, Oosterloo, T, Schiminovich, D, Stanford, S A, and van Gorkom, J. Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited. United States: N. p., 2006. Web. doi:10.1086/505526.
Croft, S, van Breugel, W, de Vries, W, Dopita, M, Martin, C, Morganti, R, Neff, S, Oosterloo, T, Schiminovich, D, Stanford, S A, & van Gorkom, J. Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited. United States. doi:10.1086/505526.
Croft, S, van Breugel, W, de Vries, W, Dopita, M, Martin, C, Morganti, R, Neff, S, Oosterloo, T, Schiminovich, D, Stanford, S A, and van Gorkom, J. Tue . "Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited". United States. doi:10.1086/505526. https://www.osti.gov/servlets/purl/899106.
@article{osti_899106,
title = {Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited},
author = {Croft, S and van Breugel, W and de Vries, W and Dopita, M and Martin, C and Morganti, R and Neff, S and Oosterloo, T and Schiminovich, D and Stanford, S A and van Gorkom, J},
abstractNote = {We present neutral hydrogen, ultraviolet, optical and near-infrared imaging, as well as optical spectroscopic observations of Minkowski's Object (MO), a star forming system at the end of a radio jet associated with NGC541 at the center of a cluster of galaxies, Abell 194. The observations strengthen the evidence, first presented in 1985, that MO is a small, peculiar galaxy in which the star formation has been triggered by the radio jet. Key new results are the discovery of a double H I cloud with a mass of 4.9 x 10{sup 8} M{sub {circle_dot}} straddling the radio jet downstream from MO at the location where the jet changes direction and decollimates; a strong detection of MO at near- and far-UV wavelengths and in H{alpha}, both of which also show a double structure; and what appear to be numerous H II regions and associated clusters in MO. The UV morphology of MO along the radio jet resembles the radio-aligned, rest-frame UV morphologies seen in many high redshift radio galaxies, which are also thought to be caused by jet-induced star formation. The UV, optical, and near-IR data show that the stellar population is dominated by a 7.5Myr-old instantaneous burst, with a total stellar mass of 1.9 x 10{sup 7} M{sub {circle_dot}}.},
doi = {10.1086/505526},
journal = {Astrophysical Journal, vol. 647, N/A, August 20, 2006, pp. 1040},
number = ,
volume = ,
place = {United States},
year = {Tue Feb 07 00:00:00 EST 2006},
month = {Tue Feb 07 00:00:00 EST 2006}
}
  • New radio and optical images of Minkowski's object, a peculiar blue object near the elliptical galaxy NGC 541 in the cluster Abell 194, are presented. The observations show that the object is a region with bright optical line and continuum emission which are morphologically related and associated with a radio jet emanating from NGC 541. Optical emission is brightest near the edges of the jet, correlated with the absence of polarized radio emission, and filamentary downstream where the radio jet is deflected and decollimated. Minkowski's object exhibits unusually bright optical continuum emission, and its spectrum resembles those of galaxies dominatedmore » by giant H II regions. Observations of the prototypical starburst galaxy NGC 7714 (Weedman et al., 1981) confirm that the optical emission from Minkowski's object is caused by the photoionization of gas by type O and B stars. 71 references.« less
  • We report the discovery, made using the Australia Telescope Compact Array, of a remarkable string of radio emission toward IRAS 16562-3959, a luminous infrared source with a bolometric luminosity of 7.0 x 10{sup 4} L{sub sun}. The radio emission arises from a compact, bright central component, two inner lobes which are separated by about 7'' and symmetrically offset from the central source, and two outer lobes which are separated by about 45''. The emission from the central object has a spectral index between 1.4 and 8.6 GHz of 0.85 {+-} 0.15, consistent with free-free emission from a thermal jet. Themore » radio emission from the lobes has spectral indices in the range characteristic of thermal emission. We suggest that the emission from the lobes arises in shocks resulting from the interaction of a collimated wind with the surrounding medium. The radio string is located within a massive dense molecular core, and is associated with extended green emission (Spitzer three-color), Herbig-Haro-type emission (2MASS K{sub s} band), and OH maser sites-all phenomena readily observed toward sites of massive star formation. We conclude that the massive core hosts a high-mass star in an early stage of evolution in which it is undergoing the ejection of a powerful collimated stellar wind, showing that jets found in the formation of low-mass stars are also produced in high-mass stars.« less
  • We present deep Spitzer/Infrared Spectrograph (IRS) spectra for complete samples of 46 2 Jy radio galaxies (0.05 < z < 0.7) and 19 3CRR FRII radio galaxies (z < 0.1), and use the detection of polycyclic aromatic hydrocarbon (PAH) features to examine the incidence of contemporaneous star formation and radio-loud active galactic nucleus (AGN) activity. Our analysis reveals PAH features in only a minority (30%) of the objects with good IRS spectra. Using the wealth of complementary data available for the 2 Jy and 3CRR samples we make detailed comparisons between a range of star formation diagnostics: optical continuum spectroscopy,more » mid- to far-IR (MFIR) color, far-IR excess and PAH detection. There is good agreement between the various diagnostic techniques: most candidates identified to have star formation activity on the basis of PAH detection are also identified using at least two of the other techniques. We find that only 35% of the combined 2 Jy and 3CRR sample show evidence for recent star formation activity (RSFA) at optical and/or MFIR wavelengths. This result argues strongly against the idea of a close link between starburst and powerful radio-loud AGN activity, reinforcing the view that, although a large fraction of powerful radio galaxies may be triggered in galaxy interactions, only a minority are triggered at the peaks of star formation activity in major, gas-rich mergers. However, we find that compact radio sources (D < 15 kpc) show a significantly higher incidence of RSFA (>75%) than their more extended counterparts ( Almost-Equal-To 15%-25%). We discuss this result in the context of a possible bias toward the selection of compact radio sources triggered in gas-rich environments.« less
  • Deep VLA maps of NGC 253 show that it has at least 35 compact radio sources similar to those in the prototypical IR starburst galaxy M82. It is noted that NGC 253 is a twin of M82 in IR spectrum and luminosity as well as distance. Some of the sources in M82 which are rapidly expanding and fading are believed to be extremely young supernova remnants. Most of the sources detected in NGC 253 are unresolved or only marginally resolved, with typical diameters no greater than 2-5 pc. If they are young supernova remnants expanding at 12,000 km/s, the sourcemore » ages are no more than 160-400 yr. This requires a supernova rate of about 1/0.1 yr. If the compact radio sources are indeed young supernova remnants, star formation must have ceased shortly after the progenitors of the current supernovae were produced. 12 references.« less
  • We present a comparison of star formation rates (SFR) determined from mid-infrared 7.7 {mu}m polycyclic aromatic hydrocarbon (PAH) luminosity [SFR(PAH)], from 1.4 GHz radio luminosity [SFR(radio)], and from far-ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst galaxies with z < 0.5 having Spitzer IRS observations. The previously adopted relation log [SFR(PAH)] = log [{nu}L {sub {nu}}(7.7 {mu}m)] - 42.57 {+-} 0.2, for SFR in M{sub sun} yr{sup -1} and {nu}L {sub {nu}}(7.7 {mu}m) the luminosity at the peak of the 7.7 {mu}m PAH feature in erg s{sup -1}, is found to agree with SFR(radio). Comparing with SFR(UV) determined independentlymore » from ultraviolet observations of the same sources with the Galaxy Evolution Explorer mission (not corrected for dust extinction), the median log [SFR(PAH)/SFR(UV)] = 1.67, indicating that only 2% of the ultraviolet continuum typically escapes extinction by dust within a starburst. This ratio SFR(PAH)/SFR(UV) depends on infrared luminosity, with the form log [SFR(PAH)/SFR(UV)] = (0.53 {+-} 0.05)log [{nu}L{sub {nu}}(7.7 {mu}m)] - 21.5 {+-} 0.18, indicating that more luminous starbursts are also dustier. Using our adopted relation between {nu}L{sub {nu}}(7.7 {mu}m) and L {sub ir}, this becomes log [SFR(PAH)/SFR(UV)]= (0.53 {+-} 0.05)log L{sub ir} - 4.11 {+-} 0.18, for L{sub ir} in L{sub sun}. Only blue compact dwarf galaxies show comparable or greater SFR(UV) compared to SFR(PAH). We also find that the ratio SFR(PAH)/SFR(UV) is similar to that in infrared-selected starbursts for a sample of Markarian starburst galaxies originally selected using optical classification, which implies that there is no significant selection effect in SFR(PAH)/SFR(UV) using starburst galaxies discovered by Spitzer. These results indicate that SFRs determined with ultraviolet luminosities require dust corrections by a factor of {approx}10 for typical local starbursts but this factor increases to >700 for the most luminous starbursts at z {approx} 2.5. Application of this factor explains why the most luminous starbursts discovered by Spitzer at z {approx} 2.5 are optically faint; with this amount of extinction, the optical magnitude of a starburst having f{sub {nu}}(7.7 {mu}m) of 1 mJy should be V{approx} 25.6.« less