Using a simple color selection based on B-, z- and K-band photometry, BzK= (z-K)_AB-(B-z)_AB>-0.2, we picked out 52 star-forming galaxies at 1.4<z<2.5 (sBzKs) from a K-band selected sample (K_Vega<22.0) in an area of ~5.5 arcmin^2 of the Hubble Ultra Deep Field (UDF). We develop a new photometric redshift method, and the error in our photometric redshifts is less than 0.02(1+z). From the photometric redshift distribution, we find the BzK color criterion can be used to select star-forming galaxies at 1.4<z<2.5 with K_Vega<22.0.
Down to K_Vega<22.0, the number counts of sBzKs increase linearly with the K-band magnitude; the sBzKs are strongly clustered, and most of them have irregular morphologies on the ACS images. They have a median reddening of E(B-V)~0.28, an average star formation rate of ~36 M_sun/yr and a typical stellar mass of 10^10 M_sun. The UV criterion for the galaxies at z~2 can select most of the faint sBzKs in the UDF, but it does not work well for bright, massive, highly-reddened, actively star-forming galaxies.
We discuss new constraints on the epoch of cosmic reionization and test the assumption that most of the ionizing photons responsible arose from high redshift star-forming galaxies. Good progress has been made in charting the end of reionization through spectroscopic studies of z~6-8 QSOs, gamma-ray bursts and galaxies expected to host Lyman-alpha emission. However, the most stringent constraints on its duration have come from the integrated optical depth, tau, of Thomson scattering to the cosmic microwave background. Using the latest data on the abundance and luminosity distribution of distant…
In recent years, the rise in the number of Lyman Break Galaxies detected at high redshifts z >= 6 has opened up the possibility of understanding early galaxy formation physics in great detail. In particular, the faint-end slope (alpha) of the Ultra-violet luminosity function (UV LF) of these galaxies is a potential probe of feedback effects that suppress star formation in low mass haloes. In this work, we propose a proof-of-concept calculation for constraining the fluctuating UV background during reionization by constraining alpha in different volumes of the Universe. Because of patchy reioniz…
Hubble Space Telescope survey of the Perseus Cluster -IV: Compact stellar systems in the Perseus Cluster core and Ultra Compact Dwarf formation in star forming filaments
Emission-Line Galaxies from the Hubble Space Telescope Probing Evolution and Reionization Spectroscopically (PEARS) Grism Survey. II: The Complete Sample
We present photometry and derived redshifts from up to eleven bandpasses for 9927 galaxies in the Hubble Ultra Deep field (UDF), covering an observed wavelength range from the near-ultraviolet (NUV) to the near-infrared (NIR) with Hubble Space Telescope observations. Our Wide Field Camera 3 (WFC3)/UV F225W, F275W, and F336W image mosaics from the ultra-violet UDF (UVUDF) imaging campaign are newly calibrated to correct for charge transfer inefficiency, and use new dark calibrations to minimize background gradients and pattern noise. Our NIR WFC3/IR image mosaics combine the imaging from the UD…
We present a characterization of the physical properties of a sample of 35 securely-detected, dusty galaxies in the deep ALMA 1.2-mm image obtained as part of the ALMA Spectroscopic Survey in the {\it Hubble} Ultra Deep Field (ASPECS) Large Program. This sample is complemented by 26 additional sources identified via an optical/infrared source positional prior. Using their well-characterized spectral energy distributions, we derive median stellar masses and star formation rates (SFR) of $4.8\times10^{10}~M_\odot$ and 30 $M_\odot$ yr$^{-1}$, and interquartile ranges of $(2.4-11.7)\times10^{10}~M…
The Abundance of Star-Forming Galaxies in the Redshift Range 8.5 to 12: New Results from the 2012 Hubble Ultra Deep Field Campaign
我们提出了最深的搜索结果，迄今为止的恒星形成星系超越红移z~8.5利用一个新的序列的近红外宽视场相机3图像的哈勃超深场。2012年9月完成的这一“UDF 12”活动使WFC 3/IR在这一领域的早期曝光量增加了一倍，使用于定位此类遥远星系的关键F105 W滤光片的曝光量增加了四倍。结合F140 W滤波器中的额外成像，大大提高了高红移候选者的保真度。使用光谱能量分布拟合技术对从深多波段近红外堆叠中选择的对象进行拟合，我们发现7个有希望的z>8.5的候选者。由于之前声称的8.5<z<10的UDF候选者都没有被我们更深的多波段成像证实，我们的活动已经改变了在这个红移范围内测量的星系丰度。虽然我们恢复了候选的UDFj-39546284（先前提出的z=10.3），但在新添加的F140 W图像中没有检测到它，这意味着它位于z=11.9或z = 2.4的强烈发射线星系。虽然没有物理上合理的模型可以解释所需的线强度缺乏莱曼α或宽带紫外线信号，没有红外光谱，我们不能排除外来的闯入者。无论如何，我们强大的z ~ 8.5 - 10样本显示了亮度密度，继续使用JWST在6个< z 10星系上观察到的平滑下降< 8. Such continuity has important implications for models of cosmic reionization and future searc…
Constraints on the $z\sim5$ Star-Forming Galaxy Luminosity Function From $\textit{Hubble Space Telescope}$ Imaging of an Unbiased and Complete Sample of Long Gamma-ray Burst Host Galaxies
Although the Hubble constant $H_0$ and spatial curvature $Ω_{K}$ have been measured with very high precision, they still suffer from some tensions. In this paper, we propose an improved method to combine the observations of ultra-compact structure in radio quasars and strong gravitational lensing with quasars acting as background sources to determine $H_0$ and $Ω_{K}$ simultaneously. By applying the distance sum rule to the time-delay measurements of 7 strong lensing systems and 120 intermediate-luminosity quasars calibrated as standard rulers, we obtain stringent constraints on the Hubble con…
We have developed a Java-based teaching tool, "Appreciating Hubble at Hyper-speed" ($\textit{AHaH}$), intended for use by students and instructors in beginning astronomy and cosmology courses, which we have made available online. This tool lets the user hypothetically traverse the Hubble Ultra Deep Field (HUDF) in three dimensions at over $\sim500\!\times\!10^{12}$ times the speed of light, from redshifts $z\!=\!0$ today to $z\!=\!6$, about 1 Gyr after the Big Bang. Users may also view the Universe in various cosmology configurations and two different geometry modes - standard geometry that in…
Extremely large surveys with future experiments like Euclid and the SKA will soon allow us to access perturbation modes close to the Hubble scale, with wavenumbers $k \sim \mathcal{H}$. If a modified gravity theory is responsible for cosmic acceleration, the Hubble scale is a natural regime for deviations from General Relativity (GR) to become manifest. The majority of studies to date have concentrated on the consequences of alternative gravity theories for the subhorizon, quasi-static regime, however. In this paper we investigate how modifications to the gravitational field equations affect p…
Listening to galaxies tuning at z ~ 2.5 - 3.0: The first strikes of the Hubble fork
我们调查的494个星系从GMASS调查中选择在z>1，主要是在其光学静止框架，使用HST图像，从CANDELS调查的形态学特性。我们认为哈勃序列的星系形态在红移2.5<z 1时形成<3. The fractions of both ellipticals and disks decrease with increasing lookback time at z>，因此在红移z=2.5-2.7及以上时，哈勃类型无法识别，大多数星系被归类为不规则星系。定量形态学分析表明，在1<z<3时，形态学参数在区分不同形态的哈勃类型时不如在低红移时有效。没有显着的形态k-校正被发现需要哈勃类型的分类，有一些例外。一般来说，不同的形态类型占据了星系的静止坐标系（U-B）色双峰的两个峰：大多数不规则星系占据蓝峰，而椭圆星系主要位于红峰，尽管有一定程度的污染。椭圆星系比不规则星系和椭圆星系分布更均匀。我们发现，在UVJ图中的星系的位置是有关其形态类型：“静止”的绘图区域主要是由椭圆形，并在较小程度上，由磁盘。我们发现，在我们的样本中，只有~33%的所有形态椭圆星系是红色和被动演化的星系。形态上被归类为椭圆星系的蓝色星系与红色星系有着显著的结构相似性。几乎所有的不规则星系都有一个恒星形成的星系光谱。此外，大多数盘在其光谱中显示出恒星形成活动的迹象，尽管在某些情况下，它们的红色连续谱表明了…
We examine whether the Hubble tension, the mismatch between early and late measurements of $H_0$, can be alleviated by ultralight scalar fields in the early universe, and we assess its plausibility within UV physics. Since their energy density needs to rapidly redshift away, we explore decays to massless fields around the era of matter-radiation equality. We highlight a concrete implementation of ultralight pseudo-scalars, axions, that decay to an abelian dark sector. This scenario circumvents major problems of other popular realizations of early universe scalar models in that it uses a regula…
Dark photon is a massive vector field which interacts only with the physical photon through the kinetic mixing. This coupling is assumed to be weak so that the dark photon becomes almost unobservable in processes with elementary particles, but can serve as a dark matter particle. We argue that in very early Universe ($z>3000$) this vector field may have the equation of state of radiation ($w=1/3$) but later behaves as cold dark matter ($w=0$). This may slightly change the expansion rate of the Universe at early time and reduce the value of the sound horizon of baryon acoustic oscillations (sta…
We consider an ultra-light scalar field with a mass comparable to (or lighter than) the Hubble parameter of the present universe, and calculate the time evolution of the energy-momentum tensor of the vacuum fluctuations generated during and before inflation until the late-time radiation-dominated and matter-dominated universe. The equation of state changes from $w=1/3$ in the early universe to $w=-1$ at present, and it can give a candidate for the dark energy that we observe today. It then oscillates between $w=-1$ and $1$ with the amplitude of the energy density decaying as $a^{-3}$. If the f…
