Small-Scale Systems of Galaxies. III. X-Ray-detected Elliptical+Spiral Galaxy Pairs in Low-Density Environments

Grützbauch, Ruth; Trinchieri, G.; Rampazzo, R.; Held, E. V.; Rizzi, L.; Sulentic, J. W.; Zeilinger, W. W.

doi:10.1086/509657

Cited by 12 publications

(17 citation statements)

References 83 publications

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“…The SF quenching mechanisms of hot gas in early-type neighbors could be similar to those of a hot intracluster medium of galaxy clusters acting on late-type galaxies in it, which are hydrodynamic processes such as thermal evaporation, strangulation, ram pressure stripping, or viscous stripping (Park & Choi 2009;). Indeed, the X-ray observations of galaxies in pairs with mixed morphology show evidence for extended X-ray halos of the early type that surround the late type, which supports our interpretation (Grützbauch et al 2007). In addition, that the SSFRs in Fig.…”

Section: Fig 6 Same Assupporting

confidence: 86%

GOODS-Herschel: the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies

Hwang¹,

Elbaz²,

Dickinson³

et al. 2011

A&A

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Aims. We study the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies and its evolution at 0 < z < 1.2. Methods. Using the high-z galaxies in the fields of Great Observatories Origins Deep Survey (GOODS) observed by the Herschel Space Observatory in the framework of the GOODS-Herschel key program and the local IRAS or AKARI-selected galaxies in the field of Sloan Digital Sky Survey Data Release 7, we investigate the dependence of galaxy properties on the morphology of and the distance to the nearest neighbor galaxy. Results. We find that the star-formation rates (SFRs) and the specific SFRs (SSFRs) of galaxies on average depend on the morphology of and the distance to the nearest neighbor galaxy in this redshift range. When a late-type galaxy has a close neighbor galaxy, the SFR and the SSFR increase as it approaches a late-type neighbor, which is supported by Kolmogorov-Smirnov (K-S) and Monte Carlo (MC) tests with a significance level of >99%. However, the SFR and the SSFR decrease or do not change much as the galaxy approaches an early-type neighbor. The bifurcations of SFRs and SSFRs depending on the neighbor's morphology seem to occur at R n ≈ 0.5r vir,nei (virial radius of the neighbor), which is supported by K-S and MC tests with a significance level of >98%. For all redshift bins, the SSFRs of late-type galaxies interacting with late-type neighbors are increased by factors of about 1.8 ± 0.7 and 4.0 ± 1.2 compared to those of non-interacting galaxies when the pair separation is smaller than 0.5r vir,nei and 0.1r vir,nei , respectively. The dust temperature of both local and high-z late-type galaxies that strongly interact with late-type neighbors (i.e. R n ≤ 0.1r vir,nei ) appears to be higher than that of non-interacting galaxies with a significance level of 96−99%. However, the dust temperature of local late-type galaxies that strongly interact with early-type neighbors seems to be lower than or similar to that of non-interacting galaxies. Conclusions. Our results suggest that galaxy-galaxy interactions and mergers have been strongly affecting the SFR and the dust properties of star-forming galaxies over at least 8 billion years.

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Section: Fig 6 Same Assupporting

confidence: 86%

GOODS-Herschel: the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies

Hwang¹,

Elbaz²,

Dickinson³

et al. 2011

A&A

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“…X-ray and radio studies are available in the literature for a few galaxies in our sample. Compact nuclear X-ray and/or radio sources have been detected in IC 5063 (Koyama et al 1992 ( Balmaverde et al 2006), NGC 5090 (Grützbauch et al 2007), IC 4296 (Pellegrini et al 2003), NGC 5077, (Filho et al 2006), and NGC 4552 (Nagar et al 2002;Filho et al 2004). …”

Section: Comparison With Modelsmentioning

confidence: 99%

Nearby early-type galaxies with ionized gas

Annibali

Bressan

Rampazzo

et al. 2010

A&A

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122

162

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Aims. A significant fraction of early-type galaxies (ETGs) exhibit emission lines in their optical spectra. We attempt to identify the producing the emission mechanism and the ionized gas in ETGs, and its connection with the host galaxy evolution. Methods. We analyzed intermediate-resolution optical spectra of 65 ETGs, mostly located in low density environments and exhibiting spectros-copic diagnostic lines of ISM from which we had previously derived stellar population properties. To extract the emission lines from the galaxy spectra, we developed a new fitting procedure that accurately subtracts the underlying stellar continuum, and accounts for the uncertainties caused by the age-metallicity degeneracy. Results. Optical emission lines are detected in 89% of the sample. The incidence and strength of emission correlate with neither the E/S0 classification, nor the fast/slow rotator classification. By means of the classical [OIII]/Hβ versus [NII]/Hα diagnostic diagram, the nuclear galaxy activity is classified such that 72% of the galaxies with emission are LINERs, 9% are Seyferts, 12% are composite/transition objects, and 7% are non-classified. Seyferts have young luminostiy-weighted ages ( 5 Gyr), and appear, on average, significantly younger than LINERs and composites. Excluding the Seyferts from our sample, we find that the spread in the ([OIII], Hα, or [NII]) emission strength increases with the galaxy central velocity dispersion σ c . Furthermore, the [NII]/Hα ratio tends to increase with σ c . The [NII]/Hα ratio decreases with increasing galactocentric distance, indicative of either a decrease in the nebular metallicity, or a progressive "softening" of the ionizing spectrum. The average nebular oxygen abundance is slightly less than solar, and a comparison with the results obtained in Paper III from Lick indices shows that it is ≈0.2 dex lower than that of stars. Conclusions. The nuclear (r < r e /16) emission can be attributed to photoionization by PAGB stars alone only for ≈22% of the LINER/composite sample. On the other hand, we cannot exclude an important role of PAGB star photoionization at larger radii. For the major fraction of the sample, the nuclear emission is consistent with excitation caused by either a low-accretion rate AGN or fast shocks (200-500 km s −1 ) in a relatively gas poor environment (n 100 cm −3 ), or both. The derived [SII]6717/6731 ratios are consistent with the low gas densities required by the shock models. The derived nebular metallicities are indicative of either an external origin of the gas, or an overestimate of the oxygen yields by SN models.

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“…The dwarf galaxy sample studied here is fully described in Grützbauch et al (2007) and Grützbauch et al (2009). All galaxies are members of poor galaxy groups dominated by a bright galaxy pair composed of an elliptical (E) and a spiral (S).…”

Section: Sample Selectionmentioning

confidence: 99%

Nature vs. nurture in the low-density environment: structure and evolution of early-type dwarf galaxies in poor groups

Annibali

Grützbauch

Rampazzo

et al. 2011

A&A

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We present the stellar population properties of 13 dwarf galaxies residing in poor groups (low-density environment, LDE) observed with VIMOS at VLT. Ages, metallicities, and [α/Fe] ratios were derived within an r < r e /2 aperture from the Lick indices Hβ, Mgb, Fe5270, and Fe5335 through comparison with our simple stellar population (SSP) models that account for variable [α/Fe] ratios. For a fiducial subsample of 10 early-type dwarfs, we derived median values and scatters around the medians of 5.7 ± 4.4 Gyr, −0.26 ± 0.28, and −0.04 ± 0.33 for age, log Z/Z , and [α/Fe], respectively. For a selection of bright early-type galaxies (ETGs) from an earlier sample residing in a comparable environment, we derive median values of 9.8 ± 4.1 Gyr, 0.06 ± 0.16, and 0.18 ± 0.13 for the same stellar population parameters. It follows that dwarfs are on average younger, less metal rich, and less enhanced in the α-elements than giants, in agreement with the extrapolation to the low-mass regime of the scaling relations derived for giant ETGs. From the total (dwarf+giant) sample, we find that age ∝σ 0.39±0.22 , Z ∝ σ 0.80±0.16 , and α/Fe ∝ σ 0.42±0.22 . We also find correlations with morphology, in the sense that the metallicity and the [α/Fe] ratio increase with the Sersic index n or with the bulge-to-total light fraction B/T . The presence of a strong morphology-[α/Fe] relation appears to contradict the possible evolution along the Hubble sequence from low B/T (low n) to high B/T (high n) galaxies. We also investigate the role played by environment by comparing the properties of our LDE dwarfs with those of Coma red passive dwarfs from the literature. We find possible evidence that LDE dwarfs experienced more prolonged star formations than Coma dwarfs, however larger data samples are needed to draw firmer conclusions.

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Small-Scale Systems of Galaxies. III. X-Ray-detected Elliptical+Spiral Galaxy Pairs in Low-Density Environments

Cited by 12 publications

References 83 publications

GOODS-Herschel: the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies

GOODS-Herschel: the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies

Nearby early-type galaxies with ionized gas

Nature vs. nurture in the low-density environment: structure and evolution of early-type dwarf galaxies in poor groups

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