اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDetermining Star Formation Rates for Infrared Galaxies
178
0
0.0
(
0
)
تأليف
G.H. Rieke
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 um or extinction-corrected Paschen-alpha luminosities are consistent in the total infrared luminosity = L(TIR) ~ 10^10 L_sun range. MIPS 24 micron photometry can yield star formation rates accurately from this luminosity upward: SFR(M_sun/yr) = 7.8 x 10^-10 L(24 um, L_sun) from L(TIR) = 5 x 10^9 L_sun to 10^11 L_sun, and SFR = 7.8 x 10^-10 L(24 um, L_sun) x (7.76 x 10^-11 L(24))^0.048 for higher L(TIR). For galaxies with L(TIR) >= 10^10 L_sun, these new expressions should provide SFRs to within 0.2 dex. For L(TIR) >= 10^11 L_sun, we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Pa-alpha (and presumably using any other optical or near infrared recombination lines). As a part of this work, we constructed spectral energy distribution (SED) templates for eleven luminous and ultraluminous purely star forming infrared galaxies (LIRGs and ULIRGs) and over the spectral range 0.4 microns to 30 cm. We use these templates and the SINGS data to construct average templates from 5 microns to 30 cm for infrared galaxies with L(TIR) = 5 x 10^9 to 10^13 L_sun. All of these templates are made available on line.
قيم البحث
اقرأ أيضاً
Gamma-Ray Bursts (GRBs) can be a promising tracer of cosmic star-formation rate history (CSFRH). In order to reveal the CSFRH using GRBs, it is important to understand whether they are biased tracers or not. For this purpose, it is crucial to underst
and properties of GRB host galaxies, in comparison to field galaxies. In this work, we report ALMA far-infrared (FIR) observations of six $zsim2$ IR-bright GRB host galaxies, which are selected for the brightness in IR. Among them, four host galaxies are detected for the first time in the rest-frame FIR. In addition to the ALMA data, we collected multi-wavelength data from previous studies for the six GRB host galaxies. Spectral energy distribution (SED) fitting analyses were performed with texttt{CIGALE} to investigate physical properties of the host galaxies, and to test whether active galactic nucleus (AGN) and radio components are required or not. Our results indicate that the best-fit templates of five GRB host galaxies do not require an AGN component, suggesting the absence of AGNs. One GRB host galaxy, 080207, shows a very small AGN contribution. While derived stellar masses of the three host galaxies are mostly consistent with those in previous studies, interestingly the value of star-formation rates (SFRs) of all six GRB hosts are inconsistent with previous studies. Our results indicate the importance of rest-frame FIR observations to correctly estimate SFRs by covering thermal emission from cold dust heated by star formation.
We present evolutionary synthesis models of starbursts on top of old stellar populations to investigate in detailed time evolution the relation between Ha luminosity and star formation rate (SFR). The models show that several effects have an impact o
n the ratio between L(Ha) and SFR. Metallicity different from solar abundance, a time delay between star formation and maximum Ha-luminosity, and a varying stellar initial mass function give rise to strong variations in the ratio of Ha luminosity to SFR and can cause large errors in the determination of the SFR when employing well-known calibrations. When studying star-bursting dwarf galaxies, and sub-galactic fragments at high redshift, which show SFR fluctuating on short timescales, these effects can add up to errors of two orders of magnitude compared with the calibrations. To accurately determine the true current SFR additional data in combination with models for the spectral energy distribution are needed.
Compact groups of galaxies provide insight into the role of low-mass, dense environments in galaxy evolution because the low velocity dispersions and close proximity of galaxy members result in frequent interactions that take place over extended time
scales. We expand the census of star formation in compact group galaxies by citet{tzanavaris10} and collaborators with Swift UVOT, Spitzer IRAC and MIPS 24 micron photometry of a sample of 183 galaxies in 46 compact groups. After correcting luminosities for the contribution from old stellar populations, we estimate the dust-unobscured star formation rate (SFR$_{mathrm{UV}}$) using the UVOT uvw2photometry. Similarly, we use the MIPS 24 micron photometry to estimate the component of the SFR that is obscured by dust (SFR$_{mathrm{IR}}$). We find that galaxies which are MIR-active (MIR-red), also have bluer UV colours, higher specific star formation rates, and tend to lie in H~{sc i}-rich groups, while galaxies that are MIR-inactive (MIR-blue) have redder UV colours, lower specific star formation rates, and tend to lie in H~{sc i}-poor groups. We find the SFRs to be continuously distributed with a peak at about 1 M$_{odot}$ yr$^{-1}$, indicating this might be the most common value in compact groups. In contrast, the specific star formation rate distribution is bimodal, and there is a clear distinction between star-forming and quiescent galaxies. Overall, our results suggest that the specific star formation rate is the best tracer of gas depletion and galaxy evolution in compact groups.
We use the near--infrared Brgamma hydrogen recombination line as a reference star formation rate (SFR) indicator to test the validity and establish the calibration of the {it Herschel} PACS 70 mu m emission as a SFR tracer for sub--galactic regions i
n external galaxies. Brgamma offers the double advantage of directly tracing ionizing photons and of being relatively insensitive to the effects of dust attenuation. For our first experiment, we use archival CFHT Brgamma and Ks images of two nearby galaxies: NGC,5055 and NGC,6946, which are also part of the {it Herschel} program KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel). We use the extinction corrected Brgamma emission to derive the SFR(70) calibration for H{sc ii} regions in these two galaxies. A comparison of the SFR(70) calibrations at different spatial scales, from 200 pc to the size of the whole galaxy, reveals that about 50% of the total 70mu m emission is due to dust heated by stellar populations that are unrelated to the current star formation. We use a simple model to qualitatively relate the increase of the SFR(70) calibration coefficient with decreasing region size to the star formation timescale. We provide a calibration for an unbiased SFR indicator that combines the observed Halpha with the 70 mu m emission, also for use in H{sc ii} regions. We briefly analyze the PACS 100 and 160 mu m maps and find that longer wavelengths are not as good SFR indicators as 70mu m, in agreement with previous results. We find that the calibrations show about 50% difference between the two galaxies, possibly due to effects of inclination.
We have used the Spitzer Space Telescope to study the dust properties of a sample of star-forming dwarf galaxies. The differences in the mid-infrared spectral energy distributions for these galaxies which, in general, are low metallicity systems, ind
icate differences in the physical properties, heating, and/or distribution of the dust. Specifically, these galaxies have more hot dust and/or very small grains and less PAH emission than either spiral or higher luminosity starburst galaxies. As has been shown in previous studies, there is a gradual decrease in PAH emission as a function of metallicity. Because much of the energy from star formation in galaxies is re-radiated in the mid-infrared, star-formation rate indicators based on both line and continuum measurements in this wavelength range are coming into more common usage. We show that the variations in the interstellar medium properties of galaxies in our sample, as measured in the mid-infrared, result in over an order of magnitude spread in the computed star-formation rates.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
