•HPLC-MS/MS method was developed and validated for analysis of 52 multiclass illegal dyes.•ESI polarity switching for analysis of acidic, neutral and basic analytes in one run.•Dispersive SPE ...eliminated interfering compounds.•All illegal dyes were observed with acceptable matrix effects at 100-fold dilutions.
Simultaneous determination of multiclass illegal dyes possessing different chemical properties is difficult. By using LC-MS/MS via negative/positive ion switching mode, an efficient and fast multi-residual method for simultaneous determination of multiclass 52 illegal dyes with different acidic–basic properties in foodstuffs was developed and validated during one single run, including 23 fat-soluble neutral azo dyes, 8 acidic sulfonated azo dyes, 12 triphenylmethane basic dyes, three basic indole dyes, three xanthene dyes, one quinoline dye, and two anthraquinones dyes. The illegal dyes were extracted with methanol-acetonitrile and further purified with d-SPE procedure to reduce interference. Sample dilution with 100-fold was used for the elimination of matrix effects of the quantitation of LC-MS/MS analysis. Validation data showed the good recoveries in the range of 71.2–111.2%, with relative standard deviations less than 20%, suggesting the developed method is suitable for the identification and quantitation of multiclass illegal dyes at trace levels in foods.
Actualmente, el género y la diversidad como objeto de análisis, se entrelazan y fortalecen sus vínculos a través de la red que en esencia permite que la comunicación fluya en todo sentido desde una ...perspectiva interdisciplinaria e internacional que debe ser contemplada por toda institución educativa.
The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and efficient black hole finder. We present a simple mid-infrared color criterion, W1 - W2 > or =, slanted 0.8 (i.e., 3.4 -4.6 > ...or =, slanted 0.8, Vega), which identifies 61.9 + or - 5.4 active galactic nucleus (AGN) candidates per deg super(2) to a depth of W2 ~ 15.0. Uiis implies a much larger census of luminous AGNs than found by typical wide-area surveys, attributable to the fact that mid-infrared selection identifies both unobscured (type 1) and obscured (type 2) AGNs. Optical and soft X-ray surveys alone are highly biased toward only unobscured AGNs, while this simple WISE selection likely identifies even heavily obscured, Compton-thick AGNs. Using deep, public data in the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the mid-infrared depth considered, 160 mu Jy at 4.6 mu m, this simple criterion identifies 78% of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. and the reliability is 95%. We explore the demographics, multiwavelength properties and redshift distribution of WISE-selected AGN candidates in the COSMOS field.
ABSTRACT
The
FourStar
galaxy evolution survey (ZFOURGE) is a 45 night legacy program with the
FourStar
near-infrared camera on Magellan and one of the most sensitive surveys to date. ZFOURGE covers a ...total of 400 arcmin
2
in cosmic fields CDFS, COSMOS and UDS, overlapping CANDELS. We present photometric catalogs comprising >70,000 galaxies, selected from ultradeep
K
s
-band detection images (25.5–26.5 AB mag, 5
σ
, total), and >80% complete to
K
s
< 25.3–25.9 AB. We use 5 near-IR medium-bandwidth filters (
J
1
,
J
2
,
J
3
,
H
s
,
H
l
) as well as broad-band
K
s
at 1.05–2.16
μ
m to 25–26 AB at a seeing of ∼0.″5. Each field has ancillary imaging in 26–40 filters at 0.3–8
μ
m. We derive photometric redshifts and stellar population properties. Comparing with spectroscopic redshifts indicates a photometric redshift uncertainty
σ
z
= 0.010, 0.009, and 0.011 in CDFS, COSMOS, and UDS. As spectroscopic samples are often biased toward bright and blue sources, we also inspect the photometric redshift differences between close pairs of galaxies, finding
σ
z
,pairs
= 0.01–0.02 at 1 <
z
< 2.5. We quantify how
σ
z
,pairs
depends on redshift, magnitude, spectral energy distribution type, and the inclusion of
FourStar
medium bands.
σ
z
,pairs
is smallest for bright, blue star-forming samples, while red star-forming galaxies have the worst
σ
z
,pairs
. Including
FourStar
medium bands reduces
σ
z
,pairs
by 50% at 1.5 <
z
< 2.5. We calculate star formation rates (SFRs) based on ultraviolet and ultradeep far-IR
Spitzer
/MIPS and
Herschel
/PACS data. We derive rest-frame
U
−
V
and
V
−
J
colors, and illustrate how these correlate with specific SFR and dust emission to
z
= 3.5. We confirm the existence of quiescent galaxies at
z
∼ 3, demonstrating their SFRs are suppressed by > ×15.
The Wide-field Infrared Survey Explorer (WISE) has completed its all-sky survey in four channels at 3.4-22 mu m, detecting hundreds of millions of objects. We show that WISE colors alone are ...effective in isolating stars (or local early-type galaxies), star-forming galaxies, and strong active galactic nuclei (AGNs)/QSOs at z lap 3. We highlight three major applications of WISE colors: (1) Selection of strong AGNs/QSOs at z < or =, slant 3 using W1 - W2 > 0.8 and W2 < 15.2 criteria, producing a better census of this population. (2) Selection of dust-obscured, type-2 AGN/QSO candidates. (3) Selection of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 with extremely red colors, r - W4 > 14 or well-detected 22 mu m sources lacking detections in the 3.4 and 4.6 mu m bands. Optical spectroscopy of a small number of these high-redshift ULIRG candidates confirms our selection, and reveals a possible trend that optically fainter or r - W4 redder candidates are at higher redshifts.
Context.
The Mid-Infrared Instrument (MIRI) onboard the
James Webb
Space Telescope (JWST) will provide imaging, coronagraphy, low-resolution spectroscopy, and medium-resolution spectroscopy at ...unprecedented sensitivity levels in the mid-infrared wavelength range. The Medium Resolution Spectrometer (MRS) of MIRI is an integral field spectrograph that provides diffraction-limited spectroscopy between 4.9 and 28.3 μm, within a field of view (FOV) varying from ∼13 to ∼56 arcsec square. The design for MIRI MRS conforms with the goals of the JWST mission to observe high redshift galaxies and to study cosmology as well as observations of galactic objects, and stellar and planetary systems.
Aims.
From ground testing, we calculate the physical parameters essential for general observers and calibrating the wavelength solution and resolving power of the MRS which is critical for maximizing the scientific performance of the instrument.
Methods.
We have used ground-based observations of discrete spectral features in combination with Fabry-Perot etalon spectra to characterize the wavelength solution and spectral resolving power of the MRS. We present the methodology used to derive the MRS spectral characterization, which includes the precise wavelength coverage of each MRS sub-band, computation of the resolving power as a function of wavelength, and measuring slice-dependent spectral distortions.
Results.
The ground calibration of the MRS shows that it will cover the wavelength ranges from 4.9 to 28.3 μm, divided in 12 overlapping spectral sub-bands. The resolving power is
R
≳ 3500 in channel 1,
R
≳ 3000 in channel 2,
R
≳ 2500 in channel 3, and
R
≳ 1500 in channel 4. The MRS spectral resolution optimizes the sensitivity for detection of spectral features with a velocity width of ∼100 km s
−1
which is characteristic of most astronomical phenomena JWST aims to study in the mid-infrared. Based on the ground test data, the wavelength calibration accuracy is estimated to be below one-tenth of a pixel (0.1 nm at 5 μm and 0.4 at 28 μm), with small systematic shifts due to the target position within a slice for unresolved sources that have a maximum amplitude of about 0.25 spectral resolution elements. The absolute wavelength calibration is presently uncertain at the level of 0.35 nm at 5 μm and 46 nm at 28 μm, and it will be refined using in-flight commissioning observations.
Conclusions.
Based on ground test data, the MRS complies with the spectral requirements for both the
R
and wavelength accuracy for which it was designed. We also present the commissioning strategies and targets that will be followed to update the spectral characterization of the MRS.
Abstract
This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star ...formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between
z
= 0 and 4. The sample covers the stellar mass range log(
M
*
/
M
⊙
) = 9.0–11.8, and SFRs relative to that on the MS,
δ
MS = SFR/SFR(MS), from 10
−1.3
to 10
2.2
. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time
t
depl
, defined as the ratio of molecular gas mass to SFR, scales as (1 +
z
)
−0.6
× (
δ
MS)
−0.44
and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass
μ
gas
depends on (
1
+
z
)
2.5
×
(
δ
MS
)
0.52
×
(
M
*
)
−
0.36
, which tracks the evolution of the specific SFR. The redshift dependence of
μ
gas
requires a curvature term, as may the mass dependences of
t
depl
and
μ
gas
. We find no or only weak correlations of
t
depl
and
μ
gas
with optical size
R
or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high
z
.
Interstellar dust and starlight are modeled for the galaxies of the project "Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel." The galaxies were observed by the Infrared Array ...Camera and the Multiband Imaging Photometer for Spitzer on Spitzer Space Telescope, and the Photodetector Array Camera and Spectrometer and the Spectral and Photometric Imaging Receiver on Herschel Space Observatory. With data from 3.6 to 500 m, dust models are strongly constrained. Using a physical dust model, for each pixel in each galaxy we estimate (1) dust surface density, (2) dust mass fraction in polycyclic aromatic hydrocarbons (PAHs), (3) distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR luminosity originating in subregions with high starlight intensity. The dust models successfully reproduce the observed global and resolved spectral energy distributions. With the angular resolution of Herschel, we obtain well-resolved maps (available online) for the dust properties. As in previous studies, we find the PAH fraction to be an increasing function of metallicity, with a threshold oxygen abundance Z/Z 0.1, but we find the data to be fitted best with increasing linearly with above a threshold value of 0.15(O/H) . We obtain total dust masses for each galaxy by summing the dust mass over the individual map pixels; these "resolved" dust masses are consistent with the masses inferred from a model fit to the global photometry. The global dust-to-gas ratios obtained from this study are found to correlate with galaxy metallicities. Systems with Z/Z 0.5 have most of their refractory elements locked up in dust, whereas in systems with Z/Z 0.3 most of these elements tend to remain in the gas phase. Within galaxies, we find that is suppressed in regions with unusually warm dust with . With knowledge of one long-wavelength flux density ratio (e.g., f160/f500), the minimum starlight intensity heating the dust ( ) can be estimated to within ∼50%, despite a variation in of more than two orders of magnitude. For the adopted dust model, dust masses can be estimated to within ∼0.2 dex accuracy using the f160/f500 flux ratio and the integrated dust luminosity, and to ∼0.07 dex accuracy using the 500 m luminosity alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions for estimating starlight heating intensity and dust mass may be useful for studies of high-redshift galaxies.
We present observed mid-infrared and optical colors and composite spectral energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars selected from Sloan Digital Sky Survey (SDSS) ...spectroscopy. A significant fraction of powerful quasars are obscured by dust and are difficult to detect in optical photometric or spectroscopic surveys. However, these may be more easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using samples of SDSS type 1 and 2 matched in redshift and O iii luminosity, we produce composite rest-frame 0.2-15 m SEDs based on SDSS, UKIDSS, and Wide-field Infrared Survey Explorer photometry and perform model fits using simple galaxy and quasar SED templates. The SEDs of type 1 and 2 quasars are remarkably similar, with the differences explained primarily by the extinction of the quasar component in the type 2 systems. For both types of quasar, the flux of the active galactic nucleus (AGN) relative to the host galaxy increases with AGN luminosity ( L O III ) and redder observed MIR color, but we find only weak dependencies of the composite SEDs on mechanical jet power as determined through radio luminosity. We conclude that luminous quasars can be effectively selected using simple MIR color criteria similar to those identified previously ( W 1 - W 2 > 0.7 ; Vega), although these criteria miss many heavily obscured objects. Obscured quasars can be further identified based on optical-IR colors (for example, ( u - W 3 AB ) > 1.4 ( W 1 - W 2 Vega ) + 3.2 ). These results illustrate the power of large statistical studies of obscured quasars selected on the basis of MIR and optical photometry.
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