Nearby early-type galaxies with ionized gas III. Analysis of line-strength indices with new stellar population models

被引：0
|
作者：
Annibali, F. [1 ,2 ]
Bressan, A. [2 ,3 ,4 ]
Rampazzo, R. [3 ]
Zeilinger, W.W. [5 ]
Danese, L. [2 ]
机构：
[1] STSCI, 3700 San Martin Drive, Baltimore, MD 21218, United States
[2] SISSA, via Beirut 4, 34014 Trieste, Italy
[3] INAF - Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
[4] Instituto Nacional de Astrofísica, Optica y Electrónica, Apdos. Postales 51 y 216, CP 72000 Puebla, Mexico
[5] Institut für Astronomie, Universität Wien, Türkenschanzstrae 17, 1180 Wien, Austria
来源：
Astronomy and Astrophysics | 1600年 / 463卷 / 02期
关键词：
Aims. The paper is devoted to the study of the underlying stellar population of a sample of 65 nearby early-type galaxies; predominantly located in low density environments; a large fraction of which show emission lines. Methods. Ages; metallicities; and [α/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances (7 apertures and 4 gradients) with new simple stellar population (SSP) models that account for the presence of α/Fe-enhancement. The SSPs cover a wide range of ages (109-16 × 109 yr); metallicities (0.0004 &le Z &le0.05); and [α/Fe] ratios (0-0.8). To derive the stellar population parameters; we use an algorithm that provides; together with the most likely solution in the (age; Z; α/Fe]); space; the probability density function along the age-metallicity degeneracy. Results. We derive a large spread in age; with SSP-equivalent ages ranging from a few to 15 Gyr. Age does not show any significant trend with central velocity dispersion σc; but E galaxies appear on average older than lenticulars. On the contrary; a significant increasing trend of metallicity and [α/Fe] with σc is observed; testifying that the chemical enrichment was more efficient and the duration of the star formation shorter in more massive galaxies. These latter two relations do not depend on galaxy morphological type. We have also sought possible correlations with the local galaxy density ρxyz; but neither metallicity nor α-enhancement show clear trends. However; we find that while low density environments (LDE) (ρxyz &le 0.4) contain very young objects (from 1 Gyr to 4 Gyr); none of the galaxies in the higher density environments (HDE) (40% of galaxies with a measured density) is younger than 5 Gyr. Considering the lack of environmental effect on the [α/Fe] ratio and the high value of [α/Fe] in some young massive objects; we argue that young galaxies in LDE are more likely due to recent rejuvenation episodes. By comparing the number of rejuvenated objects with the total number of galaxies in our sample; and by means of simple two-SSP component models; we estimate that; on average; the rejuvenation episodes do not involve more than 25% of the total galaxy mass. The good quality of the data also allow us to analyze the gradients of stellar populations. An average negative metallicity gradient Δlog Z/Δ log(r/re) ∼ -0.21 is firmly detected; while the age and α-enhancement spatial distributions within re/2 appear quite flat. These observations suggest that; in a given galaxy; the star formation proceeded on similar timescales all across the central re/2 region; but with an increasing efficiency toward the center. © ESO 2007;
D O I：
暂无
中图分类号：
学科分类号：
摘要：
Journal article (JA)
引用
收藏
页码：455 / 479
相关论文
共 45 条
  • [21] Nearby early-type galaxies with ionized gas: the UV emission from GALEX observations
    Marino, A.
    Rampazzo, R.
    Bianchi, L.
    Annibali, F.
    Bressan, A.
    Buson, L. M.
    Clemens, M. S.
    Panuzzo, P.
    Zeilinger, W. W.
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2011, 411 (01) : 311 - 331
  • [22] The SAURON project - XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies
    Kuntschner, Harald
    Emsellem, Eric
    Bacon, Roland
    Cappellari, Michele
    Davies, Roger L.
    de Zeeuw, P. Tim
    Falcon-Barroso, Jesus
    Krajnovic, Davor
    McDermid, Richard M.
    Peletier, Reynier F.
    Sarzi, Marc
    Shapiro, Kristen L.
    van den Bosch, Remco C. E.
    van de Ven, Glenn
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2010, 408 (01) : 97 - 132
  • [23] Star formation history of early-type galaxies in low density environments V. Blue line-strength indices for the nuclear region
    Longhetti, M
    Bressan, A
    Chiosi, C
    Rampazzo, R
    ASTRONOMY & ASTROPHYSICS, 1999, 345 (02) : 419 - 429
  • [24] Two-dimensional line-strength maps in three well-studied early-type galaxies
    Peletier, RF
    Vazdekis, A
    Arribas, S
    del Burgo, C
    García-Lorenzo, B
    Gutiérrez, C
    Mediavilla, E
    Prada, F
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1999, 310 (03) : 863 - 878
  • [25] The Stellar Initial Mass Function in Early-type Galaxies from Absorption Line Spectroscopy. III. Radial Gradients
    van Dokkum, Pieter
    Conroy, Charlie
    Villaume, Alexa
    Brodie, Jean
    Romanowsky, Aaron J.
    ASTROPHYSICAL JOURNAL, 2017, 841 (02):
  • [26] UNUSUAL PAH EMISSION IN NEARBY EARLY-TYPE GALAXIES: A SIGNATURE OF AN INTERMEDIATE-AGE STELLAR POPULATION?
    Vega, O.
    Bressan, A.
    Panuzzo, P.
    Rampazzo, R.
    Clemens, M.
    Granato, G. L.
    Buson, L.
    Silva, L.
    Zeilinger, W. W.
    ASTROPHYSICAL JOURNAL, 2010, 721 (02): : 1090 - 1104
  • [27] The stellar populations of early-type galaxies - I. Observations, line strengths and stellar population parameters
    Harrison, Craig D.
    Colless, Matthew
    Kuntschner, Harald
    Couch, Warrick J.
    De Propris, Roberto
    Pracy, Michael B.
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2010, 409 (04) : 1455 - 1469
  • [28] The stellar IMF in early-type galaxies from a non-degenerate set of optical line indices
    Spiniello, Chiara
    Trager, Scott
    Koopmans, Leon V. E.
    Conroy, Charlie
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2014, 438 (02) : 1483 - 1499
  • [29] Star formation history of early-type galaxies in low density environments IV. What do we learn from nuclear line-strength indices?
    Longhetti, M
    Bressan, A
    Chiosi, C
    Rampazzo, R
    ASTRONOMY & ASTROPHYSICS, 2000, 353 (03) : 917 - 929
  • [30] Stellar population analysis of MaNGA early-type galaxies: IMF dependence and systematic effects
    Bernardi, M.
    Sanchez, H. Dominguez
    Sheth, R. K.
    Brownstein, J. R.
    Lane, R. R.
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2022, 518 (03) : 4713 - 4733
12345