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Register a new userGalaxy Properties Derived with Spectral Energy Distribution Fitting in the Hawaii-Hubble Deep Field-North
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We compile multi-wavelength data from ultraviolet to infrared (IR) bands as well as redshift and source-type information for a large sample of 178,341 sources in the Hawaii-Hubble Deep Field-North field. A total of 145,635 sources among the full sample are classified/treated as galaxies and have redshift information available. We derive physical properties for these sources utilizing the spectral energy distribution fitting code CIGALE that is based on Bayesian analysis. Through various consistency and robustness check, we find that our stellar-mass and star-formation rate (SFR) estimates are reliable, which is mainly due to two facts. First, we adopt the most updated and accurate redshifts and point spread function-matched photometry; and second, we make sensible parameter choices with the CIGALE code and take into account influences of mid-IR/far-IR data, star-formation history models, and AGN contribution. We release our catalog of galaxy properties publicly (including, e.g., redshift, stellar mass, SFR, age, metallicity, dust attenuation), which is the largest of its kind in this field and should facilitate future relevant studies on formation and evolution of galaxies.
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We derive photometric redshifts (zp) for sources in the entire ($sim0.4$ deg$^2$) Hawaii-Hubble Deep Field-North (hdfn) field with the EAzY code, based on point spread function-matched photometry of 15 broad bands from the ultraviolet (bandu~band) to mid-infrared (IRAC 4.5 $mu$m). Our catalog consists of a total of 131,678 sources. We evaluate the zp~quality by comparing zp~with spectroscopic redshifts (zs) when available, and find a value of normalized median absolute deviation sigm$=$0.029 and an outlier fraction of 5.5% (outliers are defined as sources having $rm |zp - zs|/(1+zs) > 0.15$) for non-X-ray sources. More specifically, we obtain sigm$=0.024$ with 2.7% outliers for sources brighter than $R=23$~mag, sigm$=0.035$ with 7.4% outliers for sources fainter than $R=23$~mag, sigm$=$0.026 with 3.9% outliers for sources having $z<1$, and sigm$=$0.034 with 9.0% outliers for sources having $z>1$. Our zp quality shows an overall improvement over an earlier zp work that focused only on the central hdfn area. We also classify each object as star or galaxy through template spectral energy distribution fitting and complementary morphological parametrization, resulting in 4959 stars and 126,719 galaxies. Furthermore, we match our catalog with the 2~Ms {it Chandra} Deep Field-North main xray~catalog. For the 462 matched non-stellar xray~sources (281 having zs), we improve their zp~quality by adding three additional AGN templates, achieving sigm$=0.035$ and an outlier fraction of 12.5%. We make our catalog publicly available presenting both photometry and zp, and provide guidance on how to make use of our catalog.
We present a molecular line scan in the Hubble Deep Field North (HDF-N) that covers the entire 3mm window (79-115 GHz) using the IRAM Plateau de Bure Interferometer. Our CO redshift coverage spans z<0.45, 1<z<1.9 and all z>2. We reach a CO detection limit that is deep enough to detect essentially all z>1 CO lines reported in the literature so far. We have developed and applied different line searching algorithms, resulting in the discovery of 17 line candidates. We estimate that the rate of false positive line detections is ~2/17. We identify optical/NIR counterparts from the deep ancillary database of the HDF-N for seven of these candidates and investigate their available SEDs. Two secure CO detections in our scan are identified with star-forming galaxies at z=1.784 and at z=2.047. These galaxies have colors consistent with the `BzK color selection and they show relatively bright CO emission compared with galaxies of similar dust continuum luminosity. We also detect two spectral lines in the submillimeter galaxy HDF850.1 at z=5.183. We consider an additional 9 line candidates as high quality. Our observations also provide a deep 3mm continuum map (1-sigma noise level = 8.6 $mu$Jy/beam). Via a stacking approach, we find that optical/MIR bright galaxies contribute only to <50% of the SFR density at 1<z<3, unless high dust temperatures are invoked. The present study represents a first, fundamental step towards an unbiased census of molecular gas in `normal galaxies at high-z, a crucial goal of extragalactic astronomy in the ALMA era.
We determine the physical properties of a sample of SMGs in the COSMOS field that were pre-selected at the observed wavelength of $lambda_{rm obs}=1.1$ mm, and followed up at $lambda_{rm obs}=1.3$ mm with ALMA. We used MAGPHYS to fit the panchromatic (ultraviolet to radio) SEDs of 124 of the target SMGs, 19.4% of which are spectroscopically confirmed. The SED analysis was complemented by estimating the gas masses of the SMGs by using the $lambda_{rm obs}=1.3$ mm emission as a tracer of the molecular gas. The sample median and 16th-84th percentile ranges of the stellar masses, SFRs, dust temperatures, and dust and gas masses were derived to be $log(M_{star}/{rm M}_{odot})=11.09^{+0.41}_{-0.53}$, ${rm SFR}=402^{+661}_{-233}$ ${rm M}_{odot}~{rm yr}^{-1}$, $T_{rm dust}=39.7^{+9.7}_{-7.4}$ K, $log(M_{rm dust}/{rm M}_{odot})=9.01^{+0.20}_{-0.31}$, and $log(M_{rm gas}/{rm M}_{odot})=11.34^{+0.20}_{-0.23}$, respectively. The median gas-to-dust ratio and gas fraction were found to be $120^{+73}_{-30}$ and $0.62^{+0.27}_{-0.23}$, respectively. We found that 57.3% of our SMGs populate the main sequence (MS) of star-forming galaxies, while 41.9% of the sources lie above the MS by a factor of >3 (one source lies below the MS). The largest 3 GHz radio sizes are found among the MS sources. Those SMGs that appear irregular in the rest-frame UV are predominantly starbursts, while the MS SMGs are mostly disk-like. The larger radio-emitting sizes of the MS SMGs compared to starbursts is a likely indication of their more widespread, less intense star formation. The irregular UV morphologies of the starburst SMGs are likely to echo their merger nature. Our results suggest that the transition from high-$z$ SMGs to local ellipticals via compact, quiescent galaxies (cQGs) at $z sim 2$ might not be universal, and the latter population might also descend from the so-called blue nuggets.
The sensitivity and angular resolution of photometric surveys executed by the Hubble Space Telescope (HST) enable studies of individual star clusters in galaxies out to a few tens of megaparsecs. The fitting of spectral energy distributions (SEDs) of star clusters is essential for measuring their physical properties and studying their evolution. We report on the use of the publicly available Code Investigating GALaxy Emission (CIGALE) SED fitting package to derive ages, stellar masses, and reddenings for star clusters identified in the Physics at High Angular resolution in Nearby GalaxieS-HST (PHANGS-HST) survey. Using samples of star clusters in the galaxy NGC 3351, we present results of benchmark analyses performed to validate the code and a comparison to SED fitting results from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS). We consider procedures for the PHANGS-HST SED fitting pipeline, e.g., the choice of single stellar population models, the treatment of nebular emission and dust, and the use of fluxes versus magnitudes for the SED fitting. We report on the properties of clusters in NGC 3351 and find, on average, the clusters residing in the inner star-forming ring of NGC 3351 are young ($< 10$ Myr) and massive ($10^{5} M_{odot}$) while clusters in the stellar bulge are significantly older. Cluster mass function fits yield $beta$ values around -2, consistent with prior results with a tendency to be shallower at the youngest ages. Finally, we explore a Bayesian analysis with additional physically-motivated priors for the distribution of ages and masses and analyze the resulting cluster distributions.
(Abridged) In a recent work we explored the dependence of galaxy stellar population properties derived from broad-band spectral energy distribution fitting on the fitting parameters, e.g. SFHs, age grid, metallicity, IMF, dust reddening, reddening law, filter setup and wavelength coverage. In this paper we consider also redshift as a free parameter in the fit and study whether one can obtain reasonable estimates of photometric redshifts and stellar population properties at once. We use mock star-forming as well as passive galaxies placed at various redshifts (0.5 to 3) as test particles. Mock star-forming galaxies are extracted from a semi-analytical galaxy formation model. We show that for high-z star-forming galaxies photometric redshifts, stellar masses and reddening can be determined simultaneously when using a broad wavelength coverage and a wide template setup in the fit. Masses are similarly well recovered (median ~ 0.2 dex) as at fixed redshift. For old galaxies with little recent star formation masses are better recovered than in the fixed redshift case, such that the median recovered stellar mass improves by up to 0.3 dex whereas the uncertainty in the redshift accuracy increases by only ~ 0.05. However, a failure in redshift recovery also means a failure in mass recovery. As at fixed redshift mismatches in SFH and degeneracies between age, dust and now also redshift cause underestimated ages, overestimated reddening and underestimated masses. Stellar masses are best determined at low redshift without reddening in the fit (median underestimation ~ 0.1 dex for similarly well recovered redshifts). Not surprisingly, the recovery of properties is substantially better for passive galaxies. In all cases, the recovery of physical parameters is crucially dependent on the wavelength coverage adopted in the fitting. Scaling relations for the transformation of stellar masses are provided.
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