High and Low Surface Brightness Galaxies in the Local Universe. IV. Optical and 21 Centimeter Spectroscopy (original) (raw)
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The Astrophysical Journal Supplement Series, 2000
We have obtained integrated and nuclear spectra, as well as U, B, R surface photometry, for a representative sample of 196 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (M B = −14 to −22). Here we present the spectrophotometry for these galaxies. The selection of the sample and the U, B, R surface photometry is described in a companion paper (Paper I). Our goals for the project include measuring the current star formation rates and metallicities of these galaxies, and elucidating their star formation histories, as a function of luminosity and morphology. We thereby extend the work of Kennicutt (1992a) to lower luminosity systems. We anticipate that our study will be useful as a benchmark for studies of galaxies at high redshift.
Shels: Optical spectral properties of wise 22 μm selected galaxies
Astrophysical Journal, 2012
We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4 square degree region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22 µm-selected galaxies. Among 507 WISE 22 µm-selected sources with (S/N) 22µm ≥ 3 (≈ S 22µm 2.5 mJy), we identify the optical counterparts of 481 sources (∼ 98%) at R < 25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R < 21 have SHELS spectroscopic data. Most of these objects are at z < 0.8. The infrared (IR) luminosities are in the range 4.5 × 10 8 (L ⊙ ) L IR 5.4 × 10 12 (L ⊙ ). Most 22 µm-selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000Å break. The stacked spectra of the 22 µm-selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to Hβ grows with increasing IR luminosity. The optical spectra of the 22 µm-selected galaxies also show that there are some (∼ 2.8%) unusual galaxies with very strong [Ne III] λ3869, 3968 emission lines that require hard ionizing radiation such as AGN or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22 µm flux densities are enhanced if the 22 µm-selected galaxies have close late-type neighbors. The sSFR distribution of the 22 µm-selected galaxies containing active galactic nuclei (AGNs) is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy (DOG) candidates with large ( 1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z ∼ 2.
Research in Astronomy and Astrophysics, 2009
Active galactic nuclei (AGN) in low surface brightness galaxies (LSBGs) have received little attention in previous studies. In this paper, we present detailed spectral analysis of 194 LSBGs from the Impey et al. (1996) APM LSBG sample which have been observed spectroscopically by the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). Our elaborate spectral analysis enables us to carry out, for the first time, reliable spectral classification of nuclear activities in LSBGs based on the standard emission line diagnostic diagrams in a rigorous way. Star-forming galaxies are common, as found in about 52% LSBGs. We find, contrary to some of the previous claims, that the fraction of galaxies containing an AGN is significantly lower than that found in nearby normal galaxies of high surface brightness. This is qualitatively in line with the finding of Impey et al. (2001). This result holds true even within each morphological type from Sa to Sc. LSBGs having larger central stellar velocity dispersions, or larger physical sizes, tend to have a higher chance to harbor an AGN. For three AGNs with broad emission lines, the black hole masses estimated from the emission lines are broadly consistent with the well known M-σ * relation established for normal galaxies and AGNs.
An Optical Spectroscopic Atlas of Low‐Redshift Active Galactic Nuclei
The Astrophysical Journal Supplement Series, 2003
We present a spectral atlas of the H region for 215 type 1 AGNs (luminous Seyfert 1/radio galaxy nuclei and low-z quasars) up to z % 0:8. Line profiles and measures were derived from the database of intermediate resolution spectra (Re1000) with average continuum level S/N ratio %30. Parameters including rest frame equivalent width and FWHM are provided for the Fe ii opt blend at 4570, H, He ii 4686, and the [O iii] 4959, 5007 emission lines. We extract clean broad component H profiles and provide wavelength measurements at 0, 1/4, 1/2, 3/4, and 0.9 peak intensity levels in order to permit a quantitative definition of the H broad component for statistical studies. We also discuss sources of uncertainty, selection effects, and biases in our sample. The data are especially important for tests of the eigenvector 1 parameter space occupation and correlation. We show that the I Zw 1 template Fe ii opt spectrum reproduces well the observed Fe ii opt emission for a wide range of line width and strength. A detailed analysis of the data within the eigenvector 1 context is deferred to a companion paper. E 199 2. OBSERVATIONS Spectra were obtained with very similar instrumental setups yielding resolution in the range 4-7.5 Å FWHM. The median value of the S/N of our spectra is %25. shows the distribution of S/N values for our sample. We use the value for an average spectrum in the case of sources with multiple spectra of comparable quality. Spectra were obtained with the following telescopes and spectrographs: ESO 1.5 m (B&Ch), San Pedro Martir 2.2 m (B&Ch), Calar Alto 2.2 m (B&Ch), KPNO 2.2 m (Gold), and Asiago 1.82 m (B&Ch). Results based on analysis of parts of this sample can be found in
Low Surface Brightness Galaxies in the Local Universe. I. The Catalog
The Astrophysical Journal Supplement Series, 1996
We present a luminosity function for low surface brightness (LSB) galaxies identified in the APM survey of Impey et al. (1996). These galaxies have central surface brightnesses (µ(0)) in B in the range 22.0 ≤ mu(0) ≤ 25.0. Using standard maximum-likelihood estimators, we determine that the best-fit Schechter function parameters for this luminosity function (LF) are α = −1.42, M * = −18.34, and φ * = 0.0036, assuming H 0 = 100 h 100 km s −1 Mpc −1 . We compare the luminosity and number densities derived from this luminosity function to those obtained from other recent field galaxy studies and find that surveys which do not take account of the observation selection bias imposed by surface brightness are missing a substantial fraction of the galaxies in the local universe. Under our most conservative estimates, our derivation of the LF for LSB galaxies suggests that the CfA redshift survey has missed at least one third of the local galaxy population. This overlooked fraction is not enough by itself to explain the large number of faint blue galaxies observed at moderate redshift under no-evolution models, but it does help close the gap between local and moderate-redshift galaxy counts.
The Astrophysical Journal, 2015
To better characterize the global star formation (SF) activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared (FIR) color (e.g., the 60-to-100 µm color, C(60/100)] of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies [(U)LIRGs]. To this end, we exploit here a new spectroscopic approach involving only two emission lines: CO (7−6) at 372 µm and [N ii] at 205 µm ([N ii] 205µm ). For local (U)LIRGs, the ratios of the CO (7−6) luminosity (L CO (7−6) ) to the total infrared luminosity (L IR ; 8−1000 µm) are fairly tightly distributed (to within ∼0.12 dex) and show little dependence on C(60/100). This makes L CO (7−6) a good SFR tracer, which is less contaminated by active galactic nuclei (AGN) than L IR and may also be much less sensitive to metallicity than L CO (1−0) . Furthermore, the logarithmic [N ii] 205µm /CO (7−6) luminosity ratio is fairly steeply (at a slope of ∼−1.4) correlated with C(60/100), with a modest scatter (∼0.23 dex). This makes it a useful estimator on C(60/100) with an implied uncertainty of ∼0.15 [or 4 K in the dust temperature (T dust ) in the case of a graybody emission with T dust 30 K and a dust emissivity index β ≥ 1]. Our locally calibrated SFR and C(60/100) estimators are shown to be consistent with the published data of (U)LIRGs of z up to ∼6.5.
Astronomy and Astrophysics, 2016
We provide the basic integrated physical properties of all the galaxies contained in the full Cornell Atlas of Spitzer/IRS Sources (CASSIS) with available broad-band photometry from UV to 22 µm. We have collected broad-band photometric measurements in 14 wavelengths from available public surveys in order to study the spectral energy distribution (SED) of each galaxy in CASSIS, thus constructing a final sample of 1146 galaxies in the redshift range 0 < z < 2.5. The SEDs are modelled with the CIGALE code which relies on the energy balance between the absorbed stellar and the dust emission while taking into account the possible contribution due to the presence of an active galactic nucleus (AGN). We split the galaxies in three groups, a low-redshift (z < 0.1), a mid-redshift (0.1 ≤ z < 0.5) and a high-redshift (z ≥ 0.5) sub-sample and find that the vast majority of the Spitzer/IRS galaxies are star-forming and lie on or above the star-forming main sequence of the corresponding redshift. Moreover, the emission of Spitzer/IRS galaxies with z < 0.1 is mostly dominated by star-formation, galaxies in the mid-redshift bin are a mixture of star forming and AGN galaxies, while half of the galaxies with z ≥ 0.5 show moderate or high AGN activity. Additionally, using rest-frame NUV − r colour, Sérsic indices, optical [O III ] and [N II ] emission lines we explore the nature of these galaxies by investigating further their structure as well as their star-formation and AGN activity. Using a colour magnitude diagram we confirm that 97% of the galaxies with redshift smaller than 0.5 have experienced a recent star-formation episode. For a sub-sample of galaxies with available structural information and redshift smaller than 0.3 we find that early-type galaxies are placed below the main sequence, while late-type galaxies are found on the mainsequence as expected. Finally, for all the galaxies with redshift smaller than 0.5 and available optical spectral line measurements we compare the ability of CIGALE to detect the presence of an AGN in contrast to the optical spectra classification. We find that galaxies with high AGN luminosity, as calculated by CIGALE, are most likely to be classified as composite or AGNs by optical spectral lines.
The Astrophysical Journal, 2010
We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z ∼ 0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey, which includes multiwavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ∼30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [Ne ii]12.8 μm/[O iv]25.9 μm line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs. The luminosity of individual PAH components, of the continuum, and, with poorer statistics, of the neon emission lines and molecular hydrogen lines are found to be tightly correlated to the total infrared (TIR) luminosity, making individual MIR components good gauges of the total dust emission in SF galaxies. Like the TIR luminosity, these individual components can be used to estimate dust attenuation in the UV and in Hα lines based on energy balance arguments. We also propose average scaling relations between these components and dust-corrected, Hα-derived SF rates.
THE NUCLEAR NEAR-INFRARED SPECTRAL PROPERTIES OF NEARBY GALAXIES
The Astrophysical Journal Supplement Series, 2015
We present spectra of the nuclear regions of 50 nearby (D = 1 -92 Mpc, median = 20 Mpc) galaxies of morphological types E to Sm. The spectra, obtained with the Gemini Near-IR Spectrograph on the Gemini North telescope, cover a wavelength range of approximately 0.85-2.5 µm at R∼1300-1800. There is evidence that most of the galaxies host an active galactic nucleus (AGN), but the range of AGN luminosities (log (L 2−10 keV [erg s −1 ]) = 37.0-43.2) in the sample means that the spectra display a wide variety of features. Some nuclei, especially the Seyferts, exhibit a rich emission-line spectrum. Other objects, in particular the type 2 Low Ionisation Nuclear Emission Region galaxies, show just a few, weak emission lines, allowing a detailed view of the underlying stellar population. These spectra display numerous absorption features sensitive to the stellar initial mass function, as well as molecular bands arising in cool stars, and many other atomic absorption lines. We compare the spectra of subsets of galaxies known to be characterised by intermediate-age and old stellar populations, and find clear differences in their absorption lines and continuum shapes. We also examine the effect of atmospheric water vapor on the signal-to-noise ratio achieved in regions between the conventional NIR atmospheric windows, of potential interest to those planning observations of redshifted emission lines or other features affected by telluric H 2 O. Further exploitation of this data set is in progress, and the reduced spectra and data reduction tools are made available to the community.
Early-type galaxies in the near-infrared: 1.5–2.4 μm spectroscopy
Astronomy and Astrophysics, 2009
Context. Near-infrared (hereafter NIR) data may provide complementary information to the traditional optical population synthesis analysis of unresolved stellar populations because the spectral energy distribution of the galaxies in the 1-2.5 µm range is dominated by different types of stars than at optical wavelengths. Furthermore, NIR data are subjected to less absorption and hence could constrain the stellar populations in dust-obscured galaxies. Aims. We want to develop observational constraints on the stellar populations of unresolved stellar systems in the NIR. Methods. To achieve this goal we need a benchmark sample of NIR spectra of "simple" early-type galaxies, to be used for testing and calibrating the outputs of population synthesis models. We obtained low-resolution (R∼1000) long-slit spectra between 1.5 and 2.4 µm for 14 nearby early-type galaxies using SofI at the ESO 3.5-m New Technology Telescope and higher resolution (R∼3000) long-slit spectra, centered at the MgI at ∼1.51 µm for a heterogeneous sample of 5 nearby galaxies observed with ISAAC at Antu, one of the 8.2-m ESO Very Large Telescope. Results. We defined spectral indices for CO, NaI, CaI and MgI features and measured the strengths of these features in the sample galaxies. We defined a new global NIR metallicity index, suitable for abundance measurements in low-resolution spectra. Finally, we present an average NIR spectrum of an early-type galaxy, built from a homogenized subset of our sample. Conclusions. The NIR spectra of the sample galaxies show great similarity and the strength of some features does correlate with the iron abundance [Fe/H] and optical metal features of the galaxies. The data suggest that the NIR metal features, in combination with a hydrogen absorption feature may be able to break the age-metallicity degeneracy just like the Mg and Fe features in the optical wavelength range.