The aromatic features in very faint dwarf galaxies

Ronin Wu, David W. Hogg, John Moustakas

    Research output: Contribution to journalArticle

    Abstract

    We present optical and mid-infrared photometry of a statistically complete sample of 29 dwarf galaxies (Mr > - 15 mag) selected from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and observed in the mid-infrared with Spitzer IRAC. This sample contains nearby (redshift ≲0.005) galaxies 3mag fainter than previously studied samples. We compare our sample with other star-forming galaxies that have been observed with both IRAC and SDSS. We examine the relationship of the infrared color, [3.6]-[7.8], sensitive to polycyclic aromatic hydrocarbon (PAH) abundance and also hot dust and stellar continuum, with star formation rates (SFRs), oxygen abundances, and radiation hardness, all estimated by optical emission lines. Consistent with studies of more luminous dwarfs, we find that these dwarf galaxies show much redder [3.6]-[7.8] color than luminous galaxies with similar specific SFRs. Unlike luminous galaxies, we find that these dwarf galaxies show no significant dependence at all of the [3.6]-[7.8] color on SFR, oxygen abundance, or radiation hardness, despite the fact that the sample spans a significant range in all of these quantities. When the dwarfs in our sample are compared with more luminous dwarfs, we find that the [3.6]-[7.8] color, potentially tracing the PAH emission, depends on oxygen abundance and radiation hardness. However, these two parameters are correlated with one another as well; we break this degeneracy by looking at the PAH-oxygen abundance relation at a fixed radiation hardness and the PAH-hardness relation at a fixed oxygen abundance. This test shows that the [3.6]-[7.8] color in dwarf galaxies appears to depend more directly on oxygen abundance based on the data currently available.

    Original languageEnglish (US)
    Article number111
    JournalAstrophysical Journal
    Volume730
    Issue number2
    DOIs
    StatePublished - Apr 1 2011

    Fingerprint

    dwarf galaxies
    hardness
    polycyclic aromatic hydrocarbons
    oxygen
    PAH
    color
    star formation rate
    galaxies
    radiation
    infrared photometry
    tracing
    light emission
    dust
    continuums
    stars
    rate

    Keywords

    • galaxies: dwarf
    • galaxies: evolution
    • galaxies: ISM
    • infrared: galaxies
    • ISM: general
    • stars: formation

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    The aromatic features in very faint dwarf galaxies. / Wu, Ronin; Hogg, David W.; Moustakas, John.

    In: Astrophysical Journal, Vol. 730, No. 2, 111, 01.04.2011.

    Research output: Contribution to journalArticle

    Wu, Ronin ; Hogg, David W. ; Moustakas, John. / The aromatic features in very faint dwarf galaxies. In: Astrophysical Journal. 2011 ; Vol. 730, No. 2.
    @article{213af96aeff94d498bd7ec6302b6a979,
    title = "The aromatic features in very faint dwarf galaxies",
    abstract = "We present optical and mid-infrared photometry of a statistically complete sample of 29 dwarf galaxies (Mr > - 15 mag) selected from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and observed in the mid-infrared with Spitzer IRAC. This sample contains nearby (redshift ≲0.005) galaxies 3mag fainter than previously studied samples. We compare our sample with other star-forming galaxies that have been observed with both IRAC and SDSS. We examine the relationship of the infrared color, [3.6]-[7.8], sensitive to polycyclic aromatic hydrocarbon (PAH) abundance and also hot dust and stellar continuum, with star formation rates (SFRs), oxygen abundances, and radiation hardness, all estimated by optical emission lines. Consistent with studies of more luminous dwarfs, we find that these dwarf galaxies show much redder [3.6]-[7.8] color than luminous galaxies with similar specific SFRs. Unlike luminous galaxies, we find that these dwarf galaxies show no significant dependence at all of the [3.6]-[7.8] color on SFR, oxygen abundance, or radiation hardness, despite the fact that the sample spans a significant range in all of these quantities. When the dwarfs in our sample are compared with more luminous dwarfs, we find that the [3.6]-[7.8] color, potentially tracing the PAH emission, depends on oxygen abundance and radiation hardness. However, these two parameters are correlated with one another as well; we break this degeneracy by looking at the PAH-oxygen abundance relation at a fixed radiation hardness and the PAH-hardness relation at a fixed oxygen abundance. This test shows that the [3.6]-[7.8] color in dwarf galaxies appears to depend more directly on oxygen abundance based on the data currently available.",
    keywords = "galaxies: dwarf, galaxies: evolution, galaxies: ISM, infrared: galaxies, ISM: general, stars: formation",
    author = "Ronin Wu and Hogg, {David W.} and John Moustakas",
    year = "2011",
    month = "4",
    day = "1",
    doi = "10.1088/0004-637X/730/2/111",
    language = "English (US)",
    volume = "730",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
    publisher = "IOP Publishing Ltd.",
    number = "2",

    }

    TY - JOUR

    T1 - The aromatic features in very faint dwarf galaxies

    AU - Wu, Ronin

    AU - Hogg, David W.

    AU - Moustakas, John

    PY - 2011/4/1

    Y1 - 2011/4/1

    N2 - We present optical and mid-infrared photometry of a statistically complete sample of 29 dwarf galaxies (Mr > - 15 mag) selected from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and observed in the mid-infrared with Spitzer IRAC. This sample contains nearby (redshift ≲0.005) galaxies 3mag fainter than previously studied samples. We compare our sample with other star-forming galaxies that have been observed with both IRAC and SDSS. We examine the relationship of the infrared color, [3.6]-[7.8], sensitive to polycyclic aromatic hydrocarbon (PAH) abundance and also hot dust and stellar continuum, with star formation rates (SFRs), oxygen abundances, and radiation hardness, all estimated by optical emission lines. Consistent with studies of more luminous dwarfs, we find that these dwarf galaxies show much redder [3.6]-[7.8] color than luminous galaxies with similar specific SFRs. Unlike luminous galaxies, we find that these dwarf galaxies show no significant dependence at all of the [3.6]-[7.8] color on SFR, oxygen abundance, or radiation hardness, despite the fact that the sample spans a significant range in all of these quantities. When the dwarfs in our sample are compared with more luminous dwarfs, we find that the [3.6]-[7.8] color, potentially tracing the PAH emission, depends on oxygen abundance and radiation hardness. However, these two parameters are correlated with one another as well; we break this degeneracy by looking at the PAH-oxygen abundance relation at a fixed radiation hardness and the PAH-hardness relation at a fixed oxygen abundance. This test shows that the [3.6]-[7.8] color in dwarf galaxies appears to depend more directly on oxygen abundance based on the data currently available.

    AB - We present optical and mid-infrared photometry of a statistically complete sample of 29 dwarf galaxies (Mr > - 15 mag) selected from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and observed in the mid-infrared with Spitzer IRAC. This sample contains nearby (redshift ≲0.005) galaxies 3mag fainter than previously studied samples. We compare our sample with other star-forming galaxies that have been observed with both IRAC and SDSS. We examine the relationship of the infrared color, [3.6]-[7.8], sensitive to polycyclic aromatic hydrocarbon (PAH) abundance and also hot dust and stellar continuum, with star formation rates (SFRs), oxygen abundances, and radiation hardness, all estimated by optical emission lines. Consistent with studies of more luminous dwarfs, we find that these dwarf galaxies show much redder [3.6]-[7.8] color than luminous galaxies with similar specific SFRs. Unlike luminous galaxies, we find that these dwarf galaxies show no significant dependence at all of the [3.6]-[7.8] color on SFR, oxygen abundance, or radiation hardness, despite the fact that the sample spans a significant range in all of these quantities. When the dwarfs in our sample are compared with more luminous dwarfs, we find that the [3.6]-[7.8] color, potentially tracing the PAH emission, depends on oxygen abundance and radiation hardness. However, these two parameters are correlated with one another as well; we break this degeneracy by looking at the PAH-oxygen abundance relation at a fixed radiation hardness and the PAH-hardness relation at a fixed oxygen abundance. This test shows that the [3.6]-[7.8] color in dwarf galaxies appears to depend more directly on oxygen abundance based on the data currently available.

    KW - galaxies: dwarf

    KW - galaxies: evolution

    KW - galaxies: ISM

    KW - infrared: galaxies

    KW - ISM: general

    KW - stars: formation

    UR - http://www.scopus.com/inward/record.url?scp=79953723186&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=79953723186&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/730/2/111

    DO - 10.1088/0004-637X/730/2/111

    M3 - Article

    VL - 730

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 2

    M1 - 111

    ER -