Untitled

Hansen, L.; Jørgensen, H. E.; Nørgaard-Nielsen, H. U.

doi:10.1023/a:1001527512488

Cited by 59 publications

(86 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…line-strength dilution) in the continuum spectra of CCGs is consistent with recent star formation episodes (e.g. Bertola et al 1986;JFN87;Shields & Filippenko 1990;Crawford & Fabian 1993;Hansen et al 1995;Allen 1995;Melnick et al 1997;Figs. 8e and 10 -this work).…”

Section: Summary: Towards a Complete Picture?supporting

confidence: 81%

“…As it could be expected, the effect on Mg2 is almost negligible, whereas the contrary is true for the D4000. Although Hansen et al (1995) have reported E(B − V ) ≤ 0.1 for Hydra A, other authors have found non-negligible reddening values (E(B − V ) ∼ 0.1-0.6) for several cooling flow galaxies (e.g. Hu 1992;Allen et al 1995;Allen 1995;Donahue & Voit 1993;).…”

Section: Central Spectral Indicesmentioning

confidence: 91%

“…In addition, some central galaxies show clear signatures of strong Balmer absorption lines (e.g. N 1275, Crawford & Fabian 1993; Hydra A, Hansen et al 1995, Melnick et al 1997. Allen (1995) found that the strong UV/blue continua in the spectra of a small sample of CCGs were better described by young stars than by power-law emission models.…”

Section: Central Spectral Indicesmentioning

confidence: 99%

See 2 more Smart Citations

Spectral gradients in central cluster galaxies: further evidence of star formation in cooling flows

Cardiel

Gorgas

Aragón-Salamanca

1998

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We have obtained radial gradients in the spectral features λ4000-Å break (D 4000 ) and Mg 2 for a sample of 11 central cluster galaxies (CCGs): 8 in clusters with cooling flows and 3 in clusters without. After careful removal of the emission lines found within the D 4000 and the Mg 2 bandpasses for some objects, the new data strongly confirm the correlations between line-strength indices and the cooling flow phenomenon found in our earlier study (Cardiel, Gorgas & Aragón-Salamanca 1995). We find that such correlations depend on the presence and characteristics of emission lines in the inner regions of the CCGs. The nuclear indices are correlated with the mass deposition rate (Ṁ ) only when emission lines are found in the central regions of the galaxies. The central D 4000 and Mg 2 indices in cooling flow galaxies without emission lines are completely consistent with the indices measured in CCGs in clusters without cooling flows. CCGs in cooling flow clusters exhibit a clear sequence in the D 4000 -Mg 2 plane, with a neat segregation depending on emission-line types (Heckman et al. 1989) and blue morphology (McNamara 1997). This sequence can be modelled, using stellar population models with a normal IMF, by a recent (∼ 0.1 Gyr old) burst of star formation, although model uncertainties do not allow us to completely discard a continuous star formation or a series of bursts over the last few Gyr. In CCGs with emission lines, the gradients in the spectral indices are flat or positive inside the emission-line regions, suggesting the presence of young stars. Outside the emission-line regions, and in cooling flow galaxies without emission lines, gradients are negative and consistent with those measured in CCGs in clusters without cooling flows and giant elliptical galaxies. Index gradients measured exclusively in the emission-line region correlate withṀ . Using the same population models we have estimated the radial profiles of the mass transformed into new stars. The derived profiles are remarkably parallel to the expected radial behaviour of the mass deposition rate derived from X-ray observations. Moreover, a large fraction (probably most ) of the cooling flow gas accreted into the emission-line region is converted into stars. In the light of this new data, we discuss the evolutionary sequence suggested by McNamara (1997), in which radio triggered star formation bursts take place several times during the lifetime of the cooling flow. We conclude that this scenario is consistent with the available observations.

show abstract

Section: Summary: Towards a Complete Picture?supporting

confidence: 81%

Section: Central Spectral Indicesmentioning

confidence: 91%

Section: Central Spectral Indicesmentioning

confidence: 99%

See 1 more Smart Citation

Spectral gradients in central cluster galaxies: further evidence of star formation in cooling flows

Cardiel

Gorgas

Aragón-Salamanca

1998

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…As already mentioned in the Introduction, the few X-ray spectroscopic studies for the nuclear regions of radio galaxies show that the dominant radiation mechanism is associated with Hansen et al (1987). 3C 445: the Chandra image is off-axis causing a PSF elongation along the north-west axis.…”

Section: Origin Of the Soft X-ray Emissionmentioning

confidence: 82%

Extended soft X-ray emission in 3CR radio galaxies atz< 0.3: high excitation and broad line galaxies

Balmaverde

Capetti

Grandi

et al. 2012

A&A

View full text Add to dashboard Cite

We analyze Chandra observations of diffuse soft X-ray emission associated with a complete sample of 3CR radio galaxies at z < 0.3. We focus on the properties of the spectroscopic sub-classes of high excitation galaxies (HEGs) and broad line objects (BLOs). Among the 33 HEGs we detect extended (or possibly extended) emission in about 40% of the sources; the fraction is even higher (8/10) when restricting the analysis to the objects with exposure times larger than 10 ks. In the 18 BLOs, extended emission is seen only in two objects; this lower detection rate can be ascribed to the presence of their bright X-ray nuclei that easily outshine any genuine diffuse emission. A very close correspondence between the soft X-ray and optical line morphology emerges. We also find that the ratio between [O III] and extended soft X-ray luminosity is confined within a factor of 2 around a median value of 5. Both results are similar to what is seen in Seyfert galaxies. We discuss different processes that could explain the soft X-ray emission and conclude that the photoionization of extended gas, coincident with the narrow line region, is the favored mechanism.

show abstract

“…NGC 6868, the brightest galaxy of the loose group Telescopium, an E2 galaxy, at 26.8 M pc, which has probably suffered a recent merger in its central part (Hansen et al, 1991). This galaxy will be used as our control sample.…”

Section: The Samplementioning

confidence: 99%

Globular Clusters in Compact Groups

Rocha¹,

Oliveira²,

Bolte

et al.

Eso Astrophysics Symposia

View full text Add to dashboard Cite

Abstract. We have studied globular cluster systems (GCSs) around elliptical galaxies in Hickson compact groups using multi-band deep, high quality images from Keck, VLT and CFHT. Analyzing the luminosity functions, specific frequencies, color and spatial distributions, we could determine the properties of the GCSs of those galaxies and trace their star formation histories. We have found poor populations, concentrated toward the center of the galaxies, with bimodal color distributions. The study of GCSs around galaxies in small groups are a blank on the globular cluster literature.

show abstract

Untitled

Cited by 59 publications

References 12 publications

Spectral gradients in central cluster galaxies: further evidence of star formation in cooling flows

Spectral gradients in central cluster galaxies: further evidence of star formation in cooling flows

Extended soft X-ray emission in 3CR radio galaxies atz< 0.3: high excitation and broad line galaxies

Globular Clusters in Compact Groups

Contact Info

Product

Resources

About